Dissertations / Theses on the topic 'Plant-pollinator interactions'

Previous work has demonstrated that coflowering plant species (those that flower simultaneously in the same place) can potentially compete for pollination services. Competition for pollination among plant species can negatively impact their reproductive success. To minimise competition, plants can partition the activity of shared pollinators through releasing their floral resources at different times. Resource partitioning has been studied in several individual plant species, and some guilds of plants (e.g. African acacias), but little is known about temporal changes in resources at a community level. This thesis examines the spatiotemporal changes of floral resources at a community level and its implications for pollinator activity patterns. The temporal patterns of nectar and pollen provision of 70 plant species in two different plots were investigated at Mpala, in north central Kenya between 2004 and 2006. The communities studied showed that seasonal and daily microclimatic fluctuations significantly affect flowering patterns, times of flower opening, dehiscence and nectar production; and consequently the overall amount of pollen mass and nectar volume available at different times. I explored the effects of daily temporal changes in floral resource availability on pollinator activity patterns both in a guild of Malvaceae plant species, and at the community level through pollination webs. Detailed observations of daily patterns of resource provision and floral visitation in six Malvaceae plant species showed that plants can effectively avoid competition through attracting different pollinators, and via resource partition. Examination of daily changes in resource availability and the links portrayed in plant-visitor webs revealed that visitors move from one plant species to another, actively tracking changes in floral resource provision. These results suggest that in combination with physiological limitations imposed to the pollinators by temperature, bottom-up influences are a main force shaping daily pollinator activity patterns at a community level. Competition for pollination can only occur if plant species flower simultaneously and share pollinators within the same geographic area. Competition for pollination has been investigated in at least two African communities, but none of these studies have assessed the geographic spatial scale over which competition among coflowering species might happen. With the aim of measuring the geographic distance that pollinators visiting African acacias fly whilst foraging, I used molecular techniques to conduct paternity analysis as a proxy of how far pollen is carried away from particular trees within a population of Senegalia (Acacia) mellifera. The paternity analysis showed that pollinators move on average a maximum of 60 metres from the sampled trees, and that trees producing more flowers (resources) receive more visits, confirming that if sufficient resources are available pollinators can stay within relatively small geographic areas. Pollen movement only provides a partial measurement of the genetic neighbourhood of individual plants, because genes via seed dispersal can travel longer distances than those encompassed by the pollinators foraging areas. To investigate patterns of genetic variability in S. mellifera, I used microsatellites to conduct landscape genetic analyses including 25 adult populations and 9 seedling populations. Fourteen distinctive genetic clusters separated by four main geographic barriers were identified in the analyses. Significantly higher inbreeding was found in the seedling populations than in the adult populations. I discuss the possibility that this situation has been caused by anthropogenic exploitation and fragmentation of the adult stands.

Les interaccions planta-pol·linitzador són un component essencial de la biodiversitat i la funció ecològica dels ecosistemes terrestres. Un dels principals objectius de l'ecologia de la pol·linització és descriure aquestes interaccions i comprendre els factors subjacents a la seva estructura. En aquesta tesi doctoral es presenten els resultats dels estudis duts a terme durant tres anys en una comunitat mediterrània de plantes i els seus insectes pol·linitzadors al parc natural del Garraf (NE Espanya). En el capítol 1 es van registrar les interaccions planta-pol·linitzador i es van mesurar diferents trets morfològics, fenològics i ecològics de les especies de plantes i pol·linitzadors en un intent d'establir quins d’aquest trets estructuren les relacions planta-pol·linitzador. Es van registrar 14.713 contactes entre les principals 23 espècies de plantes i 221 espècies de pol·linitzadors, que van representar 960 interaccions específiques. Trobem que un tret ecològic (densitat de flors) i un tret fenològic (temps de floració) de les plantes van ser els principals factors que expliquen les interaccions observades. Trets florals, com la restricció de la corol·la i el pol·len i la producció de nèctar per flor, van tenir un efecte menor. En el capítol 2 s’explora el paper d'un atribut floral diferent i complex, l’aroma floral, en l'estructuració de la variació temporal de les taxes de visites de pol·linitzadors en la mateixa comunitat. Trobem que les plantes que floreixen a principis de la temporada, en un moment en què les flors són més abundants però els pol·linitzadors són escassos, produeixen major quantitats de compostos volàtils que les plantes que floreixen més tard, quan els pol·linitzadors són molt més abundants en relació a les poques flors disponibles. Aquest és el primer estudi en el qual s'analitzen els patrons d'emissió de fragàncies florals a nivell comunitari. Finalment, al capítol 3 s'exploren amb més detall la importància d’aquestes fragàncies florals mitjançant un cas d’estudi realitzat en el Jardí Botànic i Ecològic de la Universitat de Bayreuth (Alemanya). En aquest estudi es va utilitzar una planta focal (la composta Cirsium arvense) i un dels seus pol·linitzadors principal (el sírfid Episyrphus balteatus). Mitjançant mesures de volàtils al laboratori, tècniques d’electroantenografia i bioassajos es va trobar que els senyals olfactius eren més importants que els senyals visuals com a atraients de E. balteatus cap a les inflorescències de C. arvense.
Plant-pollinator interactions are an essential component of biodiversity and ecological function in terrestrial ecosystems. One of the main objectives of pollination ecology is to describe these interactions and to understand the factors underlying their structure. In this PhD thesis we present the results of studies conducted over three years in a Mediterranean plant-pollinator community in the natural park of el Garraf (NE Spain). In chapter 1 we monitored plant-pollinator interactions and measured plant and pollinator traits in an attempt to establish the main drivers of plant-pollinator relationships. We recorded 14713 contacts between the main 23 plant species and 221 pollinator species, representing 960 specific interactions. We found that an ecological trait (flower density) and a phonological trait (flowering time) were the main factors explaining the observed interactions. Floral traits, such as corolla restrictiveness and pollen and nectar production per flower, had a lesser effect. In chapter 2 we explore the role of a different and complex floral attribute, floral scent, in structuring temporal variation in pollinator visitation rates in the same community. We found that plants blooming early in the season, at a time when flowers are most abundant but pollinators are scarce, produce larger amounts of volatiles than plants blooming later, when pollinators are plentiful for the few flowers available. This is the first study in which emission patterns are analysed at the community level. Floral fragrances are further explored in chapter 3, which describes a case study conducted at the Ecological Botanical Garden of the University of Bayreuth (Germany). This study involves a focal plant (the composite Cirsium arvense) and a focal pollinator (the syrphid fly Episyrphus balteatus), and uses laboratory volatile measurements, electroantennography techniques and biossays. We found that olfactory cues were more important than visual cues as attractants of E. balteatus to C. arvense inflorescences.

Ecological systems are inherently dynamic, and a primary way in which they are dynamic is through time. Individual organisms, populations, communities, species interactions, and ecosystem functions all follow a temporal progression from the past, to the present, and into the future. This temporal progression can occur over the course of minutes, hours, days, weeks, months, years, decades, or various other timescales. In this sense, temporal dynamics are an intrinsic property of all biological systems. In fact, one of the most prominent signals of recent global climate change is the significant change in the timing of biological events for a diversity of organisms. In light of this widespread pattern, there is a renewed interest in understanding the multifaceted importance of time in ecology. In this dissertation, I investigate the temporal ecology of a subalpine ecosystem, specifically focusing on flowering plant communities and plant-pollinator interactions. I examine the temporal dynamics of this system over multiple decades in response to ongoing climate change as well as over shorter time scales within a growing season. Using a 39-year record of flowering phenology, I show that species-specific shifts in the timing of flowering in response to climate change can substantially reshape a subalpine plant community over this time period. Community phylogenetic analyses reveal that these changes are largely independent of evolutionary history. Using a laboratory experiment, I show that the timing of an important harsh abiotic event-low temperatures that cause frost damage to plants-can differentially affect flowering plant species, with implications for plant demography, community structure, and interactions with pollinators. Finally, I show that plant-pollinator interactions exhibit substantial within-season temporal turnover, and that this temporal flexibility of plant-pollinator interactions from one week to the next is consistent and predictable across years. Taken together, this dissertation provides a multifaceted investigation of the temporal ecology of plant communities and plant-pollinator interactions, revealing the important consequences of ecological timing at short-term and longer-term scales.

La grande majorité des plantes à fleurs se reproduisent grâce à leurs pollinisateurs. L’évolution chez les plantes est pourtant souvent étudiée sans prendre en compte ces interactions, et cette thèse vise à mieux comprendre leur impact sur l’évolution des plantes. Dans un premier chapitre, je présenterai les effets connus des pollinisateurs sur le taux d’autofécondation des plantes et sur son évolution. Dans un second chapitre, j’ai modélisé l’évolution du taux d’autofécondation des plantes lorsque celui-ci affecte la démographie des plantes et des pollinisateurs, et l’investissement des plantes dans la pollinisation. Cette étude montre que l’évolution vers l’autofécondation peut mener à l’extinction des plantes. Dans un troisième chapitre, je m’intéresserai à l’évolution des caractéristiques florales pour des espèces qui dépendent obligatoirement du transfert de pollen entre individus : les espèces dioïques. Cette étude montre que l’attractivité des plantes peut évoluer différemment chez les individus mâles et femelles, surtout dans les grandes populations qui subissent peu de limitation en pollen. Ce résultat suggère que le dimorphisme sexuel ne menacerait pas le maintien des populations dioïques. Enfin, même si elles prennent en compte les pollinisateurs de manière sommaire, les études précédentes ont montré leur importance pour la démographie et l’évolution chez les plantes. La dernière étude de cette thèse a donc pour but de mieux décrire et quantifier les mécanismes sous-jacents au comportement du pollinisateur, en particulier concernant l’impact des traits floraux. Elle permettra une meilleure intégration des interactions plantes-pollinisateurs dans les modèles
The mode of pollination is often neglected regarding the evolution of plant traits, although the reproduction of most flowering plants is based on their interactions with pollinators. This thesis aims at a better understanding of the interplay between animal-pollination and the evolution of plant traits. First, I will present a detailed review on the interplay between plant mating system and pollinator behavior, which highlights the impact of pollinators on the immediate ecological selfing rate and on its evolution. Second, I modeled the evolution of plant selfing rate when it affects both the demography of plants and pollinators and the investment of plants in pollination. This study provides new theoretical evidence that evolution towards selfing can lead to an evolutionary suicide in some conditions. Third, I will present a modeling analysis of the impact of animal-pollination for species that compulsorily rely on outcross pollination: entomophilous dioecious species. This study revealed that under pollinator-mediated selection, attractiveness of males and females should evolve in large populations that do not suffer from pollen limitation. This result suggests that dimorphism may not be a threat for dioecious populations. Finally, although the previous models integrated pollinators in a basic way, they highlighted strong interplays between pollinators, plant demography, and the evolution of plant traits. The last study of this thesis, aims at defining and quantifying the mechanisms underlying pollinator foraging behavior, and especially the impact of plants floral traits on pollen transfer. This would allow for a better modeling of plant-pollinators interactions

Bumble bees are important pollinators of both crops and wildflowers and t heir foraging behaviour greatly affects pollination interactions. The ability to predict these interactions can be improved by understanding the factors influencing bumble bee foraging choices. One method that has been applied to bumble bee foraging with some success is the use of optimal foraging theory to predict and understand foraging choices. This study has used optimal foraging theory in an attempt to explore a number of key assumptions and factors related to bumble bee foraging: whether net rate or efficiency maximisation is a more appropriate currency for modelling bumble bees; examining the preferences of bumble bees to identify factors which may influence the accuracy of their prediction; investigating how models based on different assumptions predict bumble bee distribution across adjacent habitats; and exploring how bumble bee body mass influences flower choice and foraging behaviour. The findings of this study are discussed in terms of predicting pollinator behaviour and its impact on plant -pollinator interactions.

Neste trabalho avaliámos o impacto que a perturbação humana das comunidades da floresta nativa da ilha Terceira (Açores) tem sobre a riqueza específica e nas interações ecológicas entre plantas e polinizadores. Para o efeito selecionámos dois locais emparelhados (um bem conservado e outro degradado), em duas áreas de estudo (Lomba e Pico Galhardo) e analisámos a integridade das redes ecológicas planta-polinizador. Constatámos que nas áreas bem conservadas as interações são dominadas por espécies nativas, enquanto que nas áreas perturbadas, apesar da prevalência de plantas introduzidas, os polinizadores nativos têm um papel relevante. Em cada área houve apenas uma planta que concentrou as visitas dos polinizadores, que na sua maioria pertenceram à ordem Diptera e tiveram hábitos generalistas; Biodiversity and plant-pollinator interactions in native forest areas of Terceira island (Azores) Abstract: In this work we evaluate the effect of anthropogenic disturbance in native forest communities of Terceira island (Azores) on species richness and on plant-pollinator ecological interactions. We selected paired sampling sites (one well-preserved and one disturbed) in two study areas (Lomba and Pico Galhardo) and we analysed plant-pollinator networks integrity. We found that native species dominate in well-preserved sites whereas in disturbed sites, despite the prevalence of introduced plants, native pollinators play an important role. In each area there was a plant that received most of the insect visits, being these mainly from Diptera order and having generalist behaviour.

Els patrons de variabilitat espacial en comunitats naturals han sigut habitualment estudiats en escales espacials grans, comparant hàbitats, on la distribució d’espècies està bàsicament relacionada amb factors ambientals. Tot i això, dintre un hàbitat és possible trobar variabilitat espacial a petita escala. La variació en la ocurrència i l’abundància de les espècies al llarg de l’espai afectarà l’estructura de les interaccions ja que diferents espècies varien en les seves característiques i amb el nombre i identitat de les espècies amb qui poden interactuar. La variabilitat espacial en les comunitats pot tenir també conseqüències ecològiques i evolutives ja que la variació en la distribució de les espècies afecta el funcionament dels ecosistemes. La pol·linització és un procés clau als ecosistemes terrestres, ja que al menys el 90% de les espècies d’angiospermes depenen de la pol·linització per animals. L’objectiu general d’aquesta tesi és analitzar la relació entre l’estructura de les comunitats planta-pol·linitzador, la funció ecosistèmica, i els patrons d’interacció al llarg de l’espai. Primer, volem veure el grau de variabilitat espacial a escala local en una comunitat planta-pol·linitzador en un hàbitat uniforme i entendre els factors afectant la variabilitat. Amb tal fi analitzem l’heterogeneïtat espacial d’una comunitat de plantes i els seus pol·linitzadors en un matollar mediterrani. Mostrem que, tot i l’aparent uniformitat, tant flors com pol·linitzadors mostren uns alts nivells de variabilitat resultant en un mosaic de comunitats locals. Els recursos no són limitants, i l’abella de la mel no afecta la distribució de la comunitat de pol·linitzadors silvestres. En general mostrem que la variabilitat de la comunitat floral no és el major predictor de la comunitat de pol·linitzadors, indicant que altres factors són importants per explicar la distribució dels pol·linitzadors a escala local. Segon, ens aprofitem de la variabilitat espacial en la comunitat de pol·linitzadors en el mateix matollar mediterrani i analitzem els efectes en la funció pol·linitzadora i l’èxit reproductiu de l’espècie ginodioica Thymus vulgaris. La deposició de pol·len es veu afectada per l’estructura de la comunitat de pol·linitzadors en els dos morfs, però no hem trobat efecte dels pol·linitzadors en l’èxit reproductiu de cap dels dos morfs indicant que la pol·linització és adequada en la majoria de poblacions estudiades. El nostre estudi mostra que la variabilitat local en la composició dels pol·linitzadors pot tenir conseqüències importants en la funció pol·linitzadora, especialment en les plantes que són més dependents dels pol·linitzadors. Finalment estudiem si hi ha una relació entre les característiques florals i les visites dels pol·linitzadors en comunitats naturals, centrant-nos en el color. Tot i que els pol·linitzadors presenten preferències de color innates, la idea de que els colors d’una flor poden ser un predictor important dels seus principals pol·linitzadors és molt controvertit ja que l’elecció de flor és dependent del context. Trobem associacions consistents entre grups de pol·linitzadors i determinats colors, i aquestes associacions coincideixen amb les predites per la teoria dels síndromes de pol·linització. Tot i això, les flors amb colors similars no atreuen assemblatges de pol·linitzadors similars. L’explicació d’aquest resultat paradoxal seria que la majoria d’espècies de flors són generalistes. Veiem que a pesar de que les preferències de color dels pol·linitzadors sembla que condicionin les interaccions planta-pol·linitzador, les forces selectives sota aquestes preferències no són suficientment fortes com per mediar l’aparició i manteniment d’associacions estretes entre plantes i pol·linitzadors basades en el color.
Los patrones de variabilidad espacial en comunidades naturales han sido habitualmente estudiados en escalas espaciales grandes, comparando hábitats, donde la distribución de especies está básicamente relacionada con factores ambientales. Aun así, dentro de un hábitat es posible encontrar variabilidad espacial a pequeña escala. La variación en la ocurrencia y abundancia de las especies a lo largo del espacio afectará la estructura de las interacciones ya que las diferentes especies varían en sus características y en el nombre e identidad de las especies con quien pueden interactuar. La variabilidad espacial en las comunidades puede tener también consecuencias ecológicas y evolutivas ya que la variación en la distribución de las especies afecta el funcionamiento de los ecosistemas. La polinización es un proceso clave en los ecosistemas terrestres, donde al menos el 90% de las especies de angiospermas dependen de la polinización por animales. El objetivo general de esta tesis es analizar la relación entre la estructura de las comunidades planta-polinizador, la función ecosistémica y los patrones de interacción a lo largo del espacio. Primero, queremos ver el grado de variabilidad espacial a escala local en una comunidad planta-polinizador en un hábitat uniforme y entender los factores que afectan dicha variabilidad. Con tal objetivo analizamos la heterogeneidad espacial de una comunidad de plantas y sus polinizadores en un matorral mediterráneo. Mostramos que, a pesar de la aparente uniformidad, tanto flores como polinizadores muestran unos elevados niveles de variabilidad resultando en un mosaico de comunidades locales. Los recursos no son limitantes, y la abeja de la miel no afecta la distribución de las comunidades de polinizadores silvestres. En general mostramos que la variabilidad en la comunidad floral no es el mayor predictor de la comunidad de polinizadores, indicando que otros factores son más importantes para explicar la distribución de los polinizadores a escala local. Segundo, aprovechamos la variabilidad espacial en la comunidad de polinizadores en el mismo matorral mediterráneo y analizamos los efectos en la función polinizadora y el éxito reproductivo de la especie ginodioica Thymus vulgaris. La deposición de polen se ve afectada por la estructura de la comunidad de polinizadores en los dos morfos, pero no hemos encontrado efectos de los polinizadores en el éxito reproductivo de ninguno de los dos morfos indicando que la polinización es adecuada en la mayoría de poblaciones estudiadas. Nuestro estudio muestra que la variabilidad local en la composición de los polinizadores puede tener consecuencias importantes en la función polinizadora, especialmente en las plantas que son más dependientes de los polinizadores. Finalmente estudiamos si hay una relación entre las características florales y las visitas de los polinizadores en comunidades naturales, centrándonos en el color. Aunque los polinizadores presentan preferencias de color innatas, la idea de que el color de la flor puede ser un predictor importante de sus principales polinizadores es muy controvertida ya que la elección de flor es dependiente del contexto. Encontramos asociaciones consistentes entre grupos de polinizadores y ciertos colores, y estas asociaciones coinciden con las predichas por la teoría de los síndromes de polinización. Aun así, las flores con colores similares no atraen ensamblajes de polinizadores similares. La explicación de este resultado paradójico seria que la mayoría de especies de flores son generalistas. Vemos que a pesar de que las preferencias de color de los polinizadores parece que condicionen las interacciones planta-polinizador, las fuerzas selectivas bajo estas preferencias no son suficientemente fuertes como para mediar la aparición y mantenimiento de asociaciones estrechas entre plantas y sus polinizadores basadas en el color.
Patterns of spatial variation in species communities have been usually studied at large spatial scales, comparing different habitats, where the distribution of species is mostly related to environmental factors. However, even within a habitat is possible to find important levels of spatial variability at the local scale. Variability in species occurrence and abundance across space will affect interaction structure because species differ in their functional traits and therefore in the number and identity of species with which they may interact. Furthermore, within-habitat spatial heterogeneity in species community structure may have far-reaching ecological and evolutionary consequences because variability in the spatial distribution of the species affects the functioning of ecosystems. Pollination is a key function in terrestrial ecosystems, with almost 90% of the angiosperm species depending on animal pollinators for sexual reproduction. The general objective of this thesis is to analyze the relationship between plant-pollinator community structure, ecological function, and interaction patterns across space. First, we aim to highlight the degree of spatial variation at the local scale in a plant-pollinator community across a uniform habitat and to understand the deterministic factors affecting this variation. For this purpose we analyse the spatial heterogeneity of a community of flowering plants and their pollinators within an uninterrupted Mediterranean scrubland. Also, since the study area is a honey producing area we want to know whether wild pollinator communities were affected by honey bee abundance. We show that, in spite of the apparent physiognomic uniformity, both flowers and pollinators display high levels of heterogeneity, resulting in a mosaic of idiosyncratic local communities. Resources appear to be non-limiting, and honey bee visitation rate did not affect the distribution of the wild pollinator community. Overall, our results show that the spatial variation of the flower community is not the main predictor of the pollinator community, indicating that other factors besides flower community composition are important to explain pollinator distribution at the local scale. Second, we take advantage of the spatial variability in local pollinator community across the same Mediterranean scrubland and analyse its effects on pollination function and reproductive success in the gynodioecious Thymus vulgaris. Pollen deposition is affected by pollinator assemblage structure and composition in both morphs, but we found no effect of the pollinator assemblage on plant reproductive success in either of the two morphs, showing that pollination appears to be adequate in most of the populations sampled. Our study shows that local variation in pollinator composition may have important consequences on pollination function, especially on plants that are more dependent on pollinators. Finally, we aim to establish whether there is a relationship between floral traits and pollinator visitation in natural communities, specifically focusing on floral colour. Although pollinators show innate colour preferences, the view that the colour of a flower may be considered an important predictor of its main pollinators is highly controversial because flower choice is highly context-dependent. We found consistent associations between pollinator groups and certain colours, and these associations matched predictions of the pollination syndrome theory. However, flowers with similar colours did not attract similar pollinator assemblages. The explanation for this paradoxical result is that most flower species are pollinator generalists. We conclude that although pollinator colour preferences seem to condition plant-pollinator interactions, the selective force behind these preferences has not been strong enough to mediate the appearance and maintenance of tight colour-based plant-pollinator associations.

Les xarxes complexes serveixen als ec olegs per a estudiar les interaccions de pollinitzaci o a nivell comunitari. Actualment, es necessari construir xarxes que siguin representacions m es realistes del proc es de pol.linitzaci o per tal d'incrementar la seva utilitat pr actica. Per aix o, aquesta tesi es centra en incorporar a les xarxes la variaci o interindividual i informaci o sobre la magnitud i el signe (positiu, neutre o negatiu) dels efectes de les interaccions sobre la reproducci o de les plantes. Les esp ecies consten de poblacions d'individus amb fenotips, genotips i comportaments diferents, que per tant poden diferir en les interaccions. Aquesta variaci o intraespec ca es rellevant per molts processos ecol ogics i evolutius, per o no s'ha tengut en compte en la majoria d'estudis de xarxes planta-pol.linitzador. En els cap tols 1 i 2 s'estudien les c arregues pol.l niques d'exemplars d'insectes pol.linitzadors en dues comunitats de muntanya a Mallorca i es construeixen xarxes on els nodes dels pol.linitzadors representen individus en lloc d'esp ecies. Aquesta aproximaci o permet considerar la variaci o interindividual i aporta una nova perspectiva sobre l'estructura de les xarxes i els mecanismes que determinen les interaccions. Les xarxes de transport de pol.len a nivell d'individu tenen una densitat d'interaccions, connect ancia, grau d'anidament i diversitat d'interaccions m es baixa que les mateixes xarxes a nivell d'esp ecies, i per contra una modularitat major. Es troben aquestes difer encies perqu e les esp ecies de pol.linitzadors generalistes estan formades per individus especialistes i heterogenis en l' us de recursos. El grau d'especialitzaci o individual est a associat a la intensitat de compet encia inter- i intraespec ca. Per a que les xarxes planta-pol.linitzador representin millor les implicacions funcionals, han d'incloure mesures dels efectes de les interaccions sobre les esp ecies o de la magnitud real en qu e les esp ecies depenen d'aquestes interaccions. La freq u encia d'interacci o es considera una estimaci o v alida de la magnitud de l'efecte del pol.linitzador sobre l' exit reproductiu de la planta, per o no aporta cap informaci o del seu signe. Per exemple, en plantes amb mecanismes de producci o de llavors que no depenen d'insectes (e.g. autog amia, anemog amia), les interaccions poden tenir efectes neutres sobre la reproducci o. En el cap tol 3, per diferents plantes de dues comunitats d'estudi (costa i muntanya) es quanti ca el seu grau de depend encia dels pol.linitzadors, comparant experimentalment la producci o de llavors amb i sense insectes. L'objectiu es determinar si les esp ecies que s on m es depenents dels pol.linitzadors s on tamb e les que estan m es connectades en les xarxes de visites orals, es a dir si tenen major centralitat, nombre i diversitat d'interaccions. Nom es en una de les dues comunitats estudiades es troba aquesta relaci o, fet que suggereix que pot dependre del contexte comunitari. D'altra banda, hi ha interaccions que poden causar m es efectes negatius que positius sobre l' exit reproductiu de les plantes. Aix o pot passar quan els pol.linitzadors depositen pol.len conespec c en els estigmes, per o alhora tamb e pol.len heterospec c. La transfer encia interespec ca de pol.len es relativament comuna, perqu e sovint les esp ecies de oraci o simult ania comparteixen pol.linitzadors, i pot tenir efectes perjudicials per les plantes (e.g. p erdua de pol.len, obstrucci o dels estigmes). En el cap tol 4, s'estudien les transfer encies de pol.len interespec ques en tres comunitats andines al llarg d'un gradient altitudinal. Es construeixen xarxes dirigides representant la transfer encia de pol.len des de les esp ecies donants a les receptores i a cada interacci o de la xarxa s'hi associa un signe per representar l'efecte. Aquest signe s'obt e de la relaci o entre el pol.len conespec c i heteroespec c depositat sobre els estigmes. En totes les comunitats estudiades, les interaccions positives i neutres s on predominants, particularment en la comunitat de major altitud. Aquesta troballa suggereix que la facilitaci o entre plantes d'una comunitat pot augmentar quan les condicions pel servei de pol.linitzaci o es tornen menys favorables.
Las redes complejas sirven a los ec ologos para estudiar las interacciones de polinizaci on a nivel comunitario. Actualmente, para incrementar su utilidad pr actica, es necesario construir redes que sean representaciones lo m as realistas posibles del proceso de polinizaci on. Por este motivo, esta tesis se centra en incorporar a las redes la variaci on interindividual y informaci on sobre la magnitud y el signo (positivo, neutro o negativo) de los efectos de las interacciones sobre la reproducci on de las plantas. Las especies constan de poblaciones de individuos con fenotipos, genotipos y comportamientos distintos, que por tanto pueden diferir en sus interacciones. Esta variaci on intraespec ca es relevante para muchos procesos ecol ogicos y evolutivos, pero no se ha considerado en la mayor a de estudios de redes plantapolinizador. En los cap tulos 1 y 2 se estudian las cargas pol nicas de ejemplares de insectos polinizadores en dos comunidades de monta~na en Mallorca y se construyen redes donde los nodos de los polinizadores representan individuos en lugar de especies. Esto permite incorporar la variaci on interindividual y aportar una nueva perspectiva sobre la estructura de las redes y los mecanismos que determinan las interacciones. Las redes de transporte de polen a nivel de individuo tienen una densidad de interacciones, conectancia, anidamiento y diversidad de interacciones m as baja que las mismas redes a nivel de especies, pero una modularidad mayor. Estas diferencias ocurren porque las especies de polinizadores generalistas est an formadas por individuos especialistas y heterog eneos en la utilizaci on de recursos. El grado de especializaci on individual est a asociado a la intensidad de competencia inter- e intraespec ca. Para que las redes planta-polinizador sean m as representativas de las implicaciones funcionales deben incluir medidas de los efectos de las interacciones sobre las especies o de la magnitud real en que las especies dependen de estas interacciones. La frecuencia de interacci on se considera una estimaci on v alida del efecto del polinizador sobre el exito reproductivo de la planta, aunque no aporta informaci on sobre su signo. Por ejemplo, en plantas con mecanismos de producci on de semillas independientes de los insectos (e.g. autogamia, anemogamia), las interacciones pueden tener efectos neutros sobre la reproducci on. En el cap tulo 3, para diferentes plantas de dos comunidades de estudio (costa y monta~na) se cuanti ca el grado de dependencia de polinizadores comparando experimentalmente la producci on de semillas con y sin insectos. El objetivo es determinar si las especies m as dependientes de polinizadores son tambi en las m as conectadas en las redes, con mayor centralidad, n umero y diversidad de interacciones. S olo en una de las comunidades de estudio se encuentra esta relaci on, sugiriendo que es variable en funci on del contexto comunitario. Por otro lado, hay interacciones que pueden causar efectos m as negativos que positivos sobre el exito reproductivo de las plantas. Esto puede pasar cuando los polinizadores depositan polen conespec co y heterospec co en los estigmas. La transferencia interespec ca de polen es relativamente com un, porque a menudo las especies de oraci on simult anea comparten polinizadores, y puede tener efectos perjudiciales para las plantas (e.g. p erdida de polen, obstrucci on de estigmas). En el cap tulo 4, se estudian las transferencias de polen interespec cas en tres comunidades andinas a lo largo de un gradiente altitudinal. Se construyen redes dirigidas que representan la transferencia de polen desde las especies donantes a las receptoras y a cada interacci on se le asocia un signo mostrando el efecto. Este signo se obtiene de la relaci on entre el polen conespec co y heteroespec co depositado sobre los estigmas. En todas las comunidades estudiadas, predominan las interacciones positivas y neutras, particularmente en la comunidad de mayor altitud. Esto sugiere que la facilitaci on en una comunidad puede aumentar cuando las condiciones para la polinizaci on se vuelven menos favorables.
Ecologists use network analysis to study pollination interactions at a communitywide level. The construction of plant-pollinator networks which are realistic representations of the pollination process is fundamental to increase their usefulness and ecological meaning. For that reason, this thesis focuses on incorporating to such networks individual variation and information about the magnitude and sign (positive, neutral or negative) of interaction e ects on plant reproduction. Species consist of populations of phenotypically, genetically and behaviourally diverse individuals which thus di er in their interactions and foraging decisions. Despite its relevance for many ecological and evolutionary processes, intraspeci c variation has been overlooked in most plant-pollinator network studies. In chapters 1 and 2, pollen loads of insect pollinator individuals are studied in two mountain communities of Mallorca, and networks where pollinator nodes depict individuals instead of species are built. Such approach (network downscaling) permits to account for the variation within species and provides new insights on network interaction patterns and their causal mechanisms. Pollen-transport networks at the individual level had lower linkage density, connectance, nestedness and interaction diversity, than the same networks at the species level, but higher modularity. These di erences occur because generalist pollinator species are composed of heterogeneous specialist individuals in the use of resources. The degree of individual specialization is associated with inter- and intraspeci c competition. Plant-pollinator networks which represent more accurately functional implications should include measures of interaction e ects on species or estimates of the actual degree to which species depend on such interactions. In general, interaction frequency is considered a good surrogate of the magnitude of interaction e ects, although it does not give any information about the e ect sign. For instance, in plant species with mechanisms for producing seeds independently of pollinators (e.g. autogamy, anemogamy), interactions may have a neutral reproductive e ect. In chapter 3, the degree of reproductive dependence on pollinators is quanti ed for several plant species in two study communities (coast and mountain), comparing seed set with and without insects. The objective is to determine whether plant species which depend more on pollinators are also more connected in ower-visitation networks, i.e. have high centrality, number and diversity of interactions. Such relationship is only found in one of the two study communities, which suggests that it is community-context dependent. On the other hand, there are interactions which may cause more negative than positive e ects on plant reproductive success. This may happen when owervisitors deposit both conspeci c and heterospeci c pollen on stigmas. Such interspeci c pollen transfer is common because co- owering plants often share pollinators, and can have detrimental e ects on plant tness (e.g. pollen loss and stigma clogging). In chapter 4, interspeci c pollen transfers are studied in three high-Andean communities along a mountain altitudinal gradient. Directed networks depicting pollen transfers from donor to receptor species are constructed, and a sign is associated to each network link to represent the e ect. This sign is obtained from the study of the relationship between conspeci c and heterospeci c pollen deposited on stigmas. In all study communities, facilitative and neutral pollinator-mediated interactions among plants prevail over competition, particularly in the highest elevation community. This nding suggests that pollination facilitation in communities can increase under less favourable conditions for the pollination service, supporting previous predictions of higher incidence of facilitative interactions in stressful environments.

本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものである
Kyoto University (京都大学)
0048
新制・課程博士
博士(理学)
甲第7693号
理博第2078号
新制||理||1105(附属図書館)
UT51-99-G287
京都大学大学院理学研究科生物科学専攻
(主査)教授 山村 則男, 教授 堀 道雄, 教授 浅野 透
学位規則第4条第1項該当

Doctor of Philosophy (PhD)
A renewed focus on generalised pollinator systems has inspired a conceptual framework which highlights that spatial and temporal interactions among plants and their assemblage of pollinators can vary across the individual, population, regional and species levels. Pollination is clearly a dynamic interaction, varying in the number and interdependence of participants and the strength of the outcome of the interaction. Therefore, the role of variation in pollination is fundamental for understanding ecological dynamics of plant populations and is a major factor in the evolution and maintenance of generalised and specialised pollination systems. My study centred on these basic concepts by addressing the following questions: (1) How variable are pollinators in a generalised pollination system? To what degree do insect visitation rates and assemblage composition vary spatially among populations and temporally among flowering seasons? (2) How does variation in pollinators affect plant reproductive success? I chose to do this using a model system, Trachymene incisa subsp. incisa (Apiaceae), which is a widespread Australian herbaceous species with simple white flowers grouped into umbels that attract a high diversity of insect visitors. The Apiaceae are considered to be highly generalist in terms of pollination, due to their simple and uniform floral display and easily accessible floral rewards. Three populations of T. incisa located between 70 km and 210 km apart were studied over 2-3 years. The few studies investigating spatial and temporal variation simultaneously over geographic and yearly/seasonal scales indicate that there is a trend for more spatial than temporal variation in pollinators of generalist-pollinated plants. My study showed both spatial and temporal variation in assemblage composition among all populations and variation in insect visitation rates, in the form of a significant population by year interaction. However, removing ants from the analyses to restrict the assemblage to flying insects and the most likely pollinators, resulted in a significant difference in overall visitation rate between years but no difference in assemblage composition between the Myall Lakes and Tomago populations. These results indicate more temporal than spatial variation in the flying insect visitor assemblage of T. incisa. Foraging behaviour provides another source of variation in plant-pollinator interactions. Trachymene incisa exhibits umbels that function as either male or female at any one time and offer different floral rewards in each phase. For successful pollination, pollinators must visit both male and female umbels during a foraging trip. Insects showed both preferences and non-preferences for umbel phases in natural patches where the gender ratio was male biased. In contrast, insects showed no bias in visitation during a foraging trip or in time spent foraging on male and female umbels in experimental arrays where the gender ratio was equal. Pollinator assemblages consisting of a mixture of different pollinator types coupled with temporal variation in the assemblages of populations among years maintains generalisation at the population/local level. In addition, spatial variation in assemblages among populations maintains generalisation at the species level. Fire alters pollination in T. incisa by shifting the flowering season and reducing the abundance of flying insects. Therefore, fire plays an important role in maintaining spatial and temporal variation in this fire-prone system. Although insect pollinators are important in determining the mating opportunities of 90% of flowering plant species worldwide, few studies have looked at the effects of variation in pollinator assemblages on plant reproductive success and mating. In T. incisa, high insect visitation rates do not guarantee high plant reproductive success, indicating that the quality of visit is more important than the rate of visitation. This is shown by comparing the Agnes Banks and Myall Lakes populations in 2003: Agnes Banks received the highest visitation rate from an assemblage dominated by ants but produced the lowest reproductive output, and Myall Lakes received the lowest visitation rate by an assemblage dominated by a native bee and produced the highest seedling emergence. Interestingly, populations with different assemblage composition can produce similar percentage seed set per umbel. However, similar percentage seed set did not result in similar percentage seedling emergence. Differences among years in reproductive output (total seed production) were due to differences in umbel production (reproductive effort) and proportion of umbels with seeds, and not seed set per umbel. Trachymene incisa is self-compatible and suffers weak to intermediate levels of inbreeding depression through early stages of the life cycle when seeds are self-pollinated and biparentally inbred. Floral phenology, in the form of synchronous protandry, plays an important role in avoiding self-pollination within umbels and reducing the chance of geitonogamous pollination between umbels on the same plant. Although pollinators can increase the rate of inbreeding in T. incisa by foraging on both male and female phase umbels on the same plant or closely related plants, most consecutive insect movements were between plants not located adjacent to each other. This indicates that inbreeding is mostly avoided and that T. incisa is a predominantly outcrossing species, although further genetic analyses are required to confirm this hypothesis. A new conceptual understanding has emerged from the key empirical results in the study of this model generalised pollination system. The large differences among populations and between years indicate that populations are not equally serviced by pollinators and are not equally generalist. Insect visitation rates varied significantly throughout the day, highlighting that sampling of pollinators at one time will result in an inaccurate estimate and usually underestimate the degree of generalisation. The visitor assemblage is not equivalent to the pollinator assemblage, although non-pollinating floral visitors are likely to influence the overall effectiveness of the pollinator assemblage. Given the high degree of variation in both the number of pollinator species and number of pollinator types, I have constructed a model which includes the degree of ecological and functional specialisation of a plant species on pollinators and the variation encountered across different levels of plant organisation. This model describes the ecological or current state of plant species and their pollinators, as well as presenting the patterns of generalisation across a range of populations, which is critical for understanding the evolution and maintenance of the system. In-depth examination of pollination systems is required in order to understand the range of strategies utilised by plants and their pollinators, and I advocate a complete floral visitor assemblage approach to future studies in pollination ecology. In particular, future studies should focus on the role of introduced pollinators in altering generalised plant-pollinator systems and the contribution of non-pollinating floral visitors to pollinator assemblage effectiveness. Comparative studies involving plants with highly conserved floral displays, such as those in the genus Trachymene and in the Apiaceae, will be useful for investigating the dynamics of generalised pollination systems across a range of widespread and restricted species.

1. Insect pollinators have been shown to alter their foraging patterns in response to habitat and landscape composition, particularly in relation to changes in the availability of floral resources which provide essential pollen and nectar provisions. Changes to pollinator behaviour and community composition, may alter the distance, directness and frequency of pollen movement and thus, the compatibility and genetic relatedness of pollen transferred between plants. We still lack good understanding of how variation in the spatial and temporal availability of floral resources drives pollinator responses and in turn, affects the fitness of outcrossing plants. Knowledge in this area could contribute to improved management interventions to enhance pollination services for plant conservation. 2. Through a combination of habitat and landscape scale field experiments, I explored how the availability of floral resources at different spatial scales affected plant-pollinator interactions, pollen transfer and mating success in plant populations, particularly those isolated from conspecifics. This involved introducing different species of plants in experimental arrays across a range of study systems that varied in structure and floral availability. Over the course of the thesis, I measured the community composition and behaviour of pollinators visiting experimental arrays; focusing on traits considered important for pollen transfer (e.g. Inter-tegular ('IT') span). Pollen movement was quantified within and between populations (5-150m) and the resulting plant outcrossing rates were measured using different methods including paternity analysis and the use of a dominance inheritance system. In addition, the implications of variations in pollinator foraging and pollination services can be attributed to pollen and gene flow and subsequently the reproduction and fitness of plants were assessed as a means of predicting the impacts on longer-term plant survival. 3. Findings from this thesis demonstrate reductions in the activity density (the abundance of actively foraging pollinators) and richness of pollinators and thus, the potential for plant visitation in response to a high abundance of floral resources within a habitat. This led to disruptions in pollen transfer, illustrated through a lower incidence of intra and inter-population pollen movement, and ultimately, reduced plant outcrossing rates. In parallel, plant seed set and germination rates were also reduced in habitats with high resource availability. Changes to pollinator communities and pollination services varied with the spatial scale at which floral resources were measured. Pollinator communities (activity density, richness and IT span) were most affected by floral resource abundance at a local scale (1-50m), particularly within a 20m radius of a plant population. Intra-population pollen movement was similarly affected by floral resources at a local spatial scale (within a 1m radius of a plant population). In contrast, no effect was observed on pollinator communities, intra-population pollen movement or plant reproduction when floral resources were measured at a landscape scale (within a 100-1500m radius of a plant population). However, findings were variable across different experiments at the same scale of measurement. For instance, the availability of floral resources at a local scale did not always elicit an effect on plant reproduction. This reflects differences in plant species identity and the effects of breeding system and floral traits, illustrated through variations in visitation rates between plant species. Inconsistencies were further observed with pollinator activity density and richness, which were not related to floral resources at a habitat scale in one chapter. 4. This thesis highlights the importance of the availability of floral resources at a local scale on plant-pollinator interactions and pollination services to plants. Co-flowering plants within florally rich habitats compete for pollinators and subsequently, visitation and pollen transfer between individuals of low density plant populations is diluted rather than facilitated. This suggests that although pollinator abundance and diversity may be enhanced through florally rich habitats (e.g. habitats implemented under the agri-environment scheme), pollination services are not automatically improved for plants which are present at low frequency in the landscape. This needs to be considered when designing and implementing management for threatened or isolated plants where plants may instead benefit from focused interventions. For instance, pollination services may be increased by efforts to maximise the facilitative effect of surrounding habitats, while increasing the ability of threatened or isolated plants to withstand competition from co-flowering plants.

Butterflies fulfill a unique role among insect pollinators as long-distance flyers. This makes butterflies particularly valuable as vectors of genetic diversity among spatially isolated plant populations. Like many insects, though, butterfly populations have experienced significant declines in recent years. To help inform conservation efforts, and to investigate community and species level dynamics, I studied butterflies and their floral resources as part of a three year pollinator survey across the state of North Dakota. At the community level, I analyzed butterfly-flower interaction networks across space and time. I then examined the specialization of individual species within those networks and their contributions to network structure. I also evaluated spatial and temporal distribution patterns of monarch butterflies, regal fritillaries, and their plant resources. Results revealed dynamic spatiotemporal relationships between butterflies and their plant resources that have important implications for conservation efforts and the study of ecological communities.

Resums pendents
Les comunitats ecològiques són entitats dinàmiques l’estructura i composició de les quals està conformada per processos ecològics i per variabilitat ambiental. Degut a que les espècies interaccionen entre elles, els canvis en l’estructura i la composició de les comunitats poden alterar les xarxes d’interacció i el funcionament dels ecosistemes. En aquesta tesi estudio com un procés ecològic (la colonització d’un hàbitat per una nova espècie) i un component important de la variabilitat espacial (la grandària de l’hàbitat) afecta a les comunitats de pol·linitzadors, d’abelles i vespes, així com a les seves interaccions mutualistes i antagonistes. També investigo si aquests canvis afecten l’estructura de la xarxa d’interaccions i les conseqüències potencials sobre la funció ecosistèmica (pol·linització, reproducció de les plantes, i parasitisme).Els canvis en la composició de les comunitats de plantes són cada vegada més freqüents en el context actual de les invasions biològiques. Tot i així, les invasions de plantes normalment representen escenaris extrems de dominància ecològica i els seus efectes han sigut estudiats relativament bé. Contràriament, els efectes de la colonització dels hàbitats per espècies autòctones (per exemple, com a resultat dels canvis en la distribució geogràfica mediats pel canvi climàtic) han rebut molta menys atenció.Al Capítol 1 analitzem els efectes de l’arribada d’una nova espècie de planta autòctona a un matollar, incloent els canvis en la composició de la comunitat de pol·linitzadors, els patrons d’interacció i l’estructura de la xarxa planta-pol·linitzador, y les conseqüències per a la pol·linització i per a l’èxit reproductiu de les espècies de plantes residents. Per a això vam manipular experimentalment taques de matollar introduint una planta autòctona (planta colonitzadora d’ara endavant), ajustant el número de flors introduïdes a la quantitat de recursos florals localment disponibles. La planta colonitzadora va atraure borinots, facilitant les interaccions a les plantes residents. Les comunitats colonitzades van exhibir una generalització de la xarxa més gran, un aniuament més gran, i modificacions en la composició dels mòduls de la xarxa. Tots aquests canvis van resultar en una deposició de pol·len heteroespecífic (però no conespecífic) més gran, i va tenir efectes contrastats en l’èxit reproductiu de les plantes residents (neutral, positiu, o negatiu depenent de l’espècie). El nostre estudi mostra que les interaccions planta-pol·linitzador es reorganitzen ràpidament com a resposta a noves situacions (inclús quan la nova planta no és excessivament dominant), amb conseqüències funcionals importants en la pol·linització i en la reproducció de les plantes. La relació espècies-àrea (increment en la riquesa d’espècies amb l’àrea) és una de les lleis de l’Ecologia més antigues i fonamentals i, recentment, ha sigut estesa a la riquesa d’interaccions (relació enllaços-àrea) i a l’estructura de la xarxa (relació xarxa-àrea). Tot i així, tot i que les relacions espècies-àrea i enllaços-àrea han rebut un ampli suport d’estudis empírics, la relació entre l’estructura de la xarxa i l’àrea roman en gran part inexplorada. Entendre aquesta relació és important perquè la fragmentació antropogènica dels hàbitats està tenint impactes profunds en la configuració dels hàbitats i està reduint la grandària dels mateixos.Al Capítol 2 testem vàries hipòtesis relacionades amb les relacions espècies-àrea, enllaços-àrea, i xarxa-àrea utilitzant comunitats d’abelles i vespes nidificants en cavitats preestablertes així com la fauna associada als seus nius (hostes i parasitoides d’ara endavant, respectivament) com a sistema d’estudi. Per a obtenir nius d’abelles i vespes vam instal·lar estacions de niadors en taques d’hàbitat obert (favorable) –envoltats de bosc dens (hàbitat desfavorable)- de tres categories de grandària (petites, ~0.1 ha; mitjanes, ~5ha; i grans, hàbitat obert continu). Els nius obtinguts en cada taca van ser disseccionats i els seus contingut van ser analitzats anotant la identitat i l’abundància de cada espècie d’hoste i parasitoid. La riquesa d’hostes, parasitoides, i interaccions va incrementar de les taques petites a les mitjanes, però no de les taques mitjanes a les grans. Els enllaços per espècie van incrementar amb la grandària de la taca, però la taxa de parasitisme no va seguir cap tendència relacionada amb la grandària de la taca. L’especialització de la xarxa va disminuir de les taques petites a les mitjanes, però les taques grans van mostrar una especialització similar a la de les taques petites i mitjanes. La modularitat va disminuir de les taques petites a les mitjanes, però no va haver-hi diferències entre les taques mitjanes i les grans. El número de mòduls va incrementar amb la grandària de la taca. Els nostres resultats estan, majoritàriament, parcialment d’acord amb les relacions espècies-àrea i enllaços-àrea. L’absència de diferències entre les taques mitjanes i grans indica l’existència d’un llindar per damunt del qual la riquesa d’espècies i d’interaccions ja no està limitada per la grandària de l’hàbitat, amb implicacions importants per a la conservació. D’altra banda, els nostres resultats estan majoritàriament en desacord amb les prediccions de la relació xarxa-àrea. Suggerim que l’empobriment de les comunitats a les taques petites resulta en una limitació en l’elecció dels hostes per part dels parasitoides generalistes, donant lloc a nivells alts d’especialització ecològica i de modularitat.S’espera que els canvis en la composició de plantes afectin a les comunitats planta-pol·linitzador de múltiples maneres depenent del context floral, de l’abundància relativa de la planta colonitzadora, del seu grau de generalització, i del seu síndrome floral. La facilitació o la competència pels pol·linitzadors poden resultar en canvis predictibles en l’estructura de la xarxa i en la pol·linització, però s’espera que els efectes sobre la reproducció de les plantes siguin altament contingents a cada espècie. S’espera que la grandària de l’hàbitat afecti a les espècies i a les interaccions seguint les relacions espècies-àrea i enllaços-área. Unint les evidències empíriques amb les prediccions teòriques, desenvolupem un marc de referència per a la relació xarxa-àrea. Les respostes de les xarxes mutualistes i antagonistes als canvis són predictibles. Tot i així, les conseqüències sobre la funció ecosistèmica segueixen sent altament contingents.
Las comunidades ecológicas son entidades dinámicas cuya estructura y composición está conformada por procesos ecológicos y por variabilidad ambiental. Debido a que las especies interaccionan entre ellas, los cambios en la estructura y composición de las comunidades pueden alterar las redes de interacción y el funcionamiento de los ecosistemas. En esta tesis estudio cómo un proceso ecológico (la colonización de un hábitat por una nueva especie) y un componente importante de la variabilidad espacial (el tamaño del hábitat) afecta a las comunidades de polinizadores, de abejas y avispas, así como a sus interacciones mutualistas y antagonistas. También investigo si estos cambios afectan a la estructura de la red de interacciones y las consecuencias potenciales sobre la función ecosistémica (polinización, reproducción de las plantas, y parasitismo).Los cambios en la composición de las comunidades de plantas son cada vez más frecuentes en el contexto actual de las invasiones biológicas. Sin embargo, las invasiones de plantas normalmente representan escenarios extremos de dominancia ecológica y sus efectos han sido estudiados relativamente bien. Por el contrario, los efectos de la colonización de los hábitats por especies autóctonas (por ejemplo, como resultado de los cambios en la distribución geográfica mediados por el cambio climático) han recibido mucha menos atención.En el Capítulo 1 analizamos los efectos de la llegada de una nueva especie de planta autóctona en un matorral, incluyendo los cambios en la composición de la comunidad de polinizadores, los patrones de interacción y la estructura de la red planta-polinizador, y las consecuencias para la polinización y para el éxito reproductivo de las especies de plantas residentes. Para ello manipulamos experimentalmente parches de matorral introduciendo una planta autóctona (planta colonizadora de ahora en adelante), ajustando el número de flores introducidas a la cantidad de recursos florales localmente disponibles. La planta colonizadora atrajo a abejorros, facilitando las interacciones a las plantas residentes. Las comunidades colonizadas exhibieron una mayor generalización de la red, un mayor anidamiento, y modificaciones en la composición de los módulos de la red. Todos estos cambios resultaron en una mayor deposición de polen heteroespecífico (pero no conespecífico) y tuvo efectos contrastados en el éxito reproductivo de las plantas residentes (neutral, positivo, o negativo dependiendo de la especie). Nuestro estudio muestra que las interacciones planta-polinizador se reorganizan rápidamente en respuesta a nuevas situaciones (incluso cuando la nueva planta no es excesivamente dominante), con consecuencias funcionales importantes en la polinización y en la reproducción de las plantas.La relación especies-área (incremento de la riqueza de especies con el área) es una de las leyes de la Ecología más antiguas y fundamentales y, recientemente, ha sido extendida a la riqueza de interacciones (relación enlaces-área) y a la estructura de la red (relación red-área). Sin embargo, a pesar que las relaciones especies- y enlaces- área han recibido un soporte amplio de estudios empíricos, la relación entre la estructura de la red y el área permanece en gran parte inexplorada. Entender esta relación es importante porque la fragmentación antropogénica de los hábitats está teniendo impactos profundos en la configuración de los hábitats y está reduciendo el tamaño de los mismos.En el Capítulo 2 testamos varias hipótesis relacionadas con las relaciones especies-área, enlaces-área y red-área utilizando comunidades de abejas y avispas nidificantes en cavidades preestablecidas así como la fauna asociada a sus nidos (huéspedes y parasitoides de ahora en adelante, respectivamente) como sistema de estudio. Para obtener nidos de abejas y avispas instalamos estaciones de nidales en parches de hábitat abierto (favorable) –rodeados por bosque denso (hábitat desfavorable)- de tres categorías de tamaño (pequeños, ~0.1 ha; medianos, ~5 ha; y grandes, hábitat abierto continuo). Los nidos obtenidos en cada parche fueron diseccionados y sus contenidos fueron analizados anotando la identidad y la abundancia de cada especie de huésped y parasitoide. La riqueza de huéspedes, parasitoides, e interacciones incrementó de los parches pequeños a los medianos, pero no de los parches medianos a los grandes. Los enlaces por especie incrementaron con el tamaño del parche, pero la tasa de parasitismo no siguió ninguna tendencia relacionada con el tamaño del hábitat. La especialización de la red disminuyó de los parches pequeños a los medianos, pero los parches grandes mostraron una especialización similar a la de los parches pequeños y medianos. La modularidad disminuyó de los parches pequeños a los medianos, pero no hubo diferencias entre los parches medianos y los grandes. El número de módulos incrementó con el tamaño del parche. Nuestros resultados están, en su mayor parte, parcialmente de acuerdo con las relaciones especies-área y enlaces-área. La ausencia de diferencias entre los parches medianos y grandes indica la existencia de un umbral por encima del cual la riqueza de especies y de interacciones ya no está limitada por el tamaño del hábitat, con implicaciones importantes para la conservación. Por otro lado, nuestros resultados están mayoritariamente en desacuerdo con las predicciones de la relación red-área. Sugerimos que el empobrecimiento de las comunidades en los parches pequeños resulta en una limitación en la elección de los huéspedes por parte de los parasitoides generalistas, dando lugar a altos niveles de especialización ecológica y de modularidad.Se espera que los cambios en la composición de plantas afecten a las comunidades planta-polinizador de múltiples maneras dependiendo del contexto floral, de la abundancia relativa de la planta colonizadora, de su grado de generalización, y de su síndrome floral. La facilitación o la competencia por los polinizadores pueden resultar en cambios predecibles en la estructura de la red y en la polinización, pero se espera que los efectos sobre la reproducción de las plantas sean altamente contingentes en cada especie. Se espera que el tamaño del hábitat afecte a las especies y a las interacciones siguiendo las relaciones especies-área y enlaces-área. Uniendo las evidencias empíricas con las predicciones teóricas, desarrollamos un marco de referencia para la relación red-área. Las respuestas de las redes mutualistas y antagonistas a los cambios son predecibles. Sin embargo, las consecuencias sobre la función ecosistémica siguen siendo altamente contingentes.
Ecological communities are dynamic entities whose structure and composition are shaped by ecological processes and environmental variability. Because species interact with one another, changes in community structure and composition are likely to alter interaction networks and ecosystem functioning. In this thesis I study how an ecological process (the colonization of a habitat by a new species) and an important component of spatial variability (habitat area) affect pollinator and bee-wasp communities and their mutualistic and antagonistic interactions. I also investigate whether these changes affect interaction network structure and the potential consequences on ecosystem function (pollination, plant reproduction, and parasitism). Changes in plant community composition are becoming increasingly frequent in the current context of pervasive biological invasions. However, plant invasions usually represent extreme scenarios of ecological dominance and their effects have been relatively well studied. By contrast, the effects of habitat colonization by native species (for example, as a result of changes in geographical distribution mediated by climate change) have received much less attention.In Chapter 1 we analyze the effects of the arrival of a new native plant into a scrubland community, including changes in pollinator community composition, plant–pollinator interaction patterns and network structure, and the consequences for pollination and reproductive success of resident plant species. To do so, we experimentally manipulated patches of scrubland by introducing a native plant (henceforth colonizing plant), adjusting the number of flowers introduced to the amount of floral resources locally available. The colonizing plant attracted bumblebees, facilitating interactions to resident plants. Colonized communities exhibited higher network generalization, nestedness, and modifications in the composition of network modules. All these changes resulted in higher heterospecific (but not conspecific) pollen deposition and had contrasting effects on the reproductive success of resident plants (neutral, positive, or negative depending on the species). Our study shows that plant-pollinator interactions are rapidly rearranged in response to novel situations (even when the new plant is not overly dominant), with important functional consequences on pollination and plant reproduction.The species-area relationship (increasing species richness with area) is one of the oldest and most fundamental laws in Ecology and, in recent years, has extended to interaction richness (link-area relationship) and network structure (network-area relationship). However, although the species- and link-area relationships have received ample support from empirical studies, the relationship between network structure and area remains largely unexplored. Understanding this relationship is important because anthropogenic habitat fragmentation is having a profound impact on habitat configuration and effectively reducing the size of natural habitats.In Chapter 2 we test several hypothesis related to the species-area, link-area and network-area relationships using cavity-nesting bee-wasp communities and their nest associates (henceforth hosts and parasitoids, respectively), as a study system. To obtain bee-wasp nests we set up nest-trapping stations in patches of (favorable) open habitat -surrounded by dense forest (unfavorable habitat)- of three size categories (small, ~0.1 ha; medium, ~5 ha; and large, continuous open habitat). The nests obtained in each patch were dissected and their contents analyzed by noting the identity and abundance of each host and parasitoid species. Host, parasitoid, and interaction richness increase from small to medium patches, but not from medium to large patches. Links per species increased with patch size, but parasitism rate did not follow any patch-size-mediated trend. Network specialization decreased from small to medium patches, but large patches showed similar specialization to that of small and medium patches. Modularity decreased from small to medium patches but there were no differences between medium and large patches. The number of modules increased with patch size. Our results are mostly in partial agreement with the species-area and the link-area relationships. The lack of differences between medium and large patches indicates the existence of a threshold above which local species/link richness are no longer limited by habitat size, with important implications for conservation. On the other hand, our results are mostly in disagreement with the predictions of the network-area relationship. We suggest that community impoverishment in small patches results in limited host choice by generalist parasitoids, leading to high levels of ecological specialization and modularity. Changes in plant composition are expected to affect plant-pollinator communities in multiple ways depending on the flower context, the relative abundance of the colonizing plant, its degree of generalization, and its pollination syndrome. Facilitation or competition for pollinators may result in predictable responses in network structure and pollination, but the effects on plant reproduction are expected to be highly contingent on each species. Habitat size is expected to affect species and interactions following the species-area and the link-area relationships. Merging empirical evidence with theoretical predictions, we developed a framework for the network-area relationship. Mutualistic and antagonistic network responses to changes are predictable. However, consequences on ecosystem function remain highly contingent.

Previous studies of plant-pollinator interactions have relied on the use of floral visitation data. Although, this may be insufficient to fully characterize the diversity and strength of plant-pollinator interactions. By using pollen transport data (i.e. pollen on pollinators), new insights can be gained on the structure and function of plant-pollinator communities. Yet studies that characterize and compare pollen-transport with floral-visitation networks are scarce. Furthermore, the strength and frequency of plant-pollinator interactions can vary across temporal scales. Although, monthly and within-day variation in network structure has been little studied. By evaluating variation in network structure across these biologically relevant time scales we will gain a better understanding of the factors that shape plant-pollinator communities. Here, we build plant-pollinator interactions networks based on floral visitation and pollen transport data by observing, collecting and sampling pollen from floral visitors in a southern Appalachian floral community. We aim to 1) compare the congruence of plant-pollinator networks built on floral visitation and pollen transport data and 2) evaluate within season and within-day variation in plant-pollinator network structure. To assess floral visitation and to quantify pollen transport, four 1x40m transects were set up at the study site. Morning collections were conducted between 8:00 AM and 3:00 PM twice per week while afternoon collections took place once per week between 3:01 PM and 5:00 PM over 20 non-consecutive days. All flower visitors observed interacting with a flower’s reproductive structures (i.e. searching for pollen and nectar) were collected.All collected pollinators were processed for surface pollen loads by dabbing the body with a 3x3mm fuschin jelly cube. Each area of the body was dabbed three times to standardize sampling. Identification and quantification of pollen was done using a compound light microscope. Data was then analyzed with the “bipartite” package of R to create bipartite plant-pollinator networks. Procrustes analysis was used to identify differences in network structure. Preliminary results show that the structure of floral visitation and pollen transport networks are significantly different from each other (P <0.01). Pollen-transport network size is almost four times larger (496 links) compared to the floral-visitation network (109 links). Species in the pollen transport network tend to be more connected (connectance = 2.3) and have five times more links per species on average (5.22 links) than floral visitation networks (connectance = 1.1, links = 1.8). Within-season and within-day differences in network structure are currently being evaluated. Our results so far show that pollen transport networks at our study site captured 78% more unique interactions and, thus, provide more accurate network structure. Interpretation of pollen transfer versus floral visitation networks can have important implications for our understanding of community-level functions such as their resilience and stability.

Orientador: Felipe Wanderley Amorim
Resumo: As mudanças globais mediadas pela ação antrópica estão alterando a biodiversidade e os ecossistemas em um ritmo acelerado. Um dos principais impulsionadores dessas mudanças é a introdução de espécies exóticas em ecossistemas nativos. Entre os grupos de organismos afetados por este processo, o das plantas é reconhecido um dos mais preocupantes, uma vez que a produção primária limita o tamanho e a composição das comunidades e participa através de efeitos em cascata em interações multi-tróficas. Uma das principais relações ecológicas influenciada por esse efeito é a relação entre plantas e polinizadores, cujo papel é importante para estrutura e funcionamento das comunidades biológicas, não apenas porque as plantas fornecem recursos alimentares essenciais para muitos grupos de animais que visitam flores, mas também porque o sucesso reprodutivo da maioria das plantas com flores depende dos serviços bióticos fornecidos por estes animais. Neste contexto, a introdução de espécies de plantas exóticas invasoras pode ter impactos críticos nas interações planta-polinizador ao nível da comunidade, principalmente através da competição com espécies nativas. Como as interações planta-polinizador são cruciais para determinar a estrutura da comunidade, nesse estudo nós testamos como o crescimento rápido de uma gramínea invasora altera a composição das espécies de plantas nativas em um campo cerrado, juntamente com os impactos deste processo sobre a estrutura das interações planta-polinizador. ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The global change mediated by anthropic action is altering biodiversity and ecosystems in a fast pace. One major driver of these changes is the introduction of alien species in native ecosystems. Among the groups of organisms that are affected by this process, plants are recognized to be one of the most concern, since primary production limit global communities’ sizes and composition, and participate through cascade effects on multitrophic interactions. One crucial type of interaction that is influenced by this effect is the plant-pollinator relationship, which have an important role in the structure and functioning of biological communities, not only because plants provide essential food resources for many groups of animals that visit flowers, but also because the reproductive success of most flowering plants depends on the biotic services provided by animals. In this context, the introduction of invasive alien plant species may have critical impacts on plant-pollinator interactions at community level, mainly through competition with native species. Since plantpollinator interactions are determinants of community structure, here we evaluated how the rising of a fast-growing invasive alien grass species changes plant species composition of a Neotropical grassland community along with its impacts on the structure of plant-pollinator interactions. For this, we analyzed the changes in community composition and plantpollinator interactions over time, through the temporal turnover... (Complete abstract click electronic access below)
Mestre

I combined comparative and experimental studies in the field and in the greenhouse to examine factors influencing reproductive success in two insect-pollinated herbs, the tristylous, selfincompatible perennial Lythrum salicaria and the self-compatible, biennial Pedicularis palustris. More specifically, I explored (i) the effects of plant population characteristics on the intensity and outcome of interactions with pollinators and seed predators, (ii) whether flower morphology affects duration of stigma receptivity, and (iii) whether damage-induced reduction in floral display reduces pollinator visitation and increases pollen limitation.

As predicted, the rate of pollinator visitation tended to increase and the number of flowers probed per plant tended to decrease with increasing population size in L. salicaria, but these relationships only approached statistical significance. By taking advantage of the pollen size polymorphism that is typical of many heterostylous plants, I could show that the number of compatible pollen grains received increased with population size, and that this was associated with a reduction in pollen limitation and increased seed output per flower. The deposition of high numbers of incompatible conspecific and heterospecific pollen grains did not appear to reduce seed set.

In P. palustris, fruit set and seed predation varied markedly among populations and years, but this variation could only partly be explained by variation in population size. Fruit set was positively related to population size, and seed predation was negatively related to population size, in one of three years. Similarly, the level of pollen limitation, which was quantified in two years, varied among populations, but was not related to population size, density or isolation.

In L. salicaria, both the duration of stigma receptivity and the effect of prior self-pollination on seed output varied among style morphs. These differences may contribute to morph-specific differences in pollen limitation and seed production documented in the field.

The results of a field experiment demonstrated that damage to the shoot apex may markedly reduce fruit production in L. salicaria, and suggested that this is mainly because damage reduces flower number. I found no evidence that a reduced floral display increased the severity of pollen limitation.

Taken together, the results show that interactions with both pollinators and herbivores may markedly affect reproductive output in the two plant species, and that the intensity of both mutualistic and antagonistic interactions vary considerably in space and time. Moreover, they are consistent with the hypothesis that pollination success should depend less on population size in selfcompatible than in self-incompatible plants.

Thesis (PhD)--Stellenbosch University, 2013.
Pollinators play a fundamental role in floral evolution. They can exert selection on the flowers they visit in a plethora of different ways, ranging from innate floral preferences to differences in body size and shape and behavioural elements such as flower constancy and learning capacity. Since different pollinators exhibit differences in these characters, shifts between pollinating species are often considered the most likely drivers of floral diversification. While many lines of evidence support this claim, numerous angiosperms pollinated by a single species also exhibit floral variation. Throughout my thesis, I explore and investigate floral diversification in such species in the absence of pollinator shifts. In Chapter 2, I investigate variation in the preference of conspecific male and female pollinators for the floral traits of a sexually deceptive daisy that comprises distinct floral forms. I show that its pollinator exhibits gender-specific variation in floral preferences, and that some floral forms have specialized on the male pollinator. This chapter thus illustrates the importance of intraspecific variation in pollinator preference for floral diversification, an underappreciated mechanism in this field of research. The innate preferences of pollinators are likely to have a genetic basis, especially innate preferences that govern mate choice. Genetic structure within the pollinators of sexually deceptive plants, which mimic female insects to achieve pollination, may thus provide an important source of selection on the plants they pollinate. This depends on an association between genetic divergence and divergent mate preferences, and I explore this intriguing idea in Chapter 3. While pollinators associated with sexually deceptive floral forms did exhibit significant genetic structuring, male pollinators from different phylogeographic clades all exhibited preference for the same sexually deceptive floral form, thus rejecting this hypothesis. Another behavioural attribute of pollinators that may affect floral evolution, particularly in deceptive plant species, is learning ability. Studies on sexually deceptive orchids often report that male pollinators tend to avoid sexually deceptive flowers with experience. In Chapter 4, I systematically investigate learning abilities within male pollinators and the costs they suffer on sexually deceptive floral forms that vary in deceptiveness. Results reveal a positive relationship between the level of floral deceptiveness and the 4 associated mating costs that deceived males suffer. Pollinator learning, however, appears to occur only on the most deceptive floral forms, suggesting a link between the costs suffered to the occurrence of learning. In Chapter 4, I systematically investigate learning abilities within male pollinators and the costs they suffer on sexually deceptive floral forms that vary in deceptiveness. Results reveal a positive relationship between the level of floral deceptiveness and the associated mating costs that deceived males suffer. Pollinator learning, however, appears to occur only on the most deceptive floral forms, suggesting a link between the costs suffered to the occurrence of learning. In Chapter 5, I explore the importance of florivory damage in a polymorphic daisy. Studies on floral evolution often overlook the significance of florivorous visits and focus only on pollinator-mediated selection. I show that floral polymorphism is maintained by antagonistic selection exerted by pollinators and florivores on the same floral traits. Lastly, I focus on evolutionary history to explore similarity in the patterns of South African angiosperm evolution and the pollinator species used throughout my thesis. Molecular dating shows this pollinator exhibits broadly congruent evolutionary patterns to these angiosperms, indicative of a shared biogeography. Taken together, my thesis demonstrates the vast impact of floral visitors, in particular pollinating insects, on the evolution of floral form.
My research was funded by the National Research Foundation of South Africa (NRF) and personal funding was provided by a NRF Innovation scholarship and merit bursaries from the Botany and Zoology department at Stellenbosch University. A WhiteSci Travel Grant and financial support from Prof. Erik Svensson at Lund University also allowed me to present parts of my research at international conference.

Observation of floral visitation is an accepted method to describe plant-pollinator interactions despite potential biases. Collecting pollen from pollinators offers new insights on the structure and function of plant-pollinator communities. Furthermore, the strength and frequency of plant-pollinator interactions can vary across temporal scales. However, within-season and within-day (morning vs. evening) variation in plant-pollinator networks has been little studied. By evaluating variation in network structure across these biologically relevant time scales, we will gain a better understanding of the factors that shape plant-pollinator communities. The objectives of this study are to 1) Compare the structure of plant-pollinator networks built on floral visitation and pollen transport data, 2) Evaluate intra-annual variation in plant-pollinator network structure and 3) Evaluate variation in plant-pollinator structure within a single day (i.e. morning vs. evening). Congruence and Temporal Variation of Floral Visitation and Pollen Transport Networks in Southern Appalachia

Observation of floral visitation is an accepted method to describe plant-pollinator interactions despite potential biases. Collecting pollen from pollinators offers new insights on the structure and function of plant-pollinator communities. Furthermore, the strength and frequency of plant-pollinator interactions can vary across temporal scales. However, within-season and within-day (morning vs. evening) variation in plant-pollinator networks has been little studied. By evaluating variation in network structure across these biologically relevant time scales, we will gain a better understanding of the factors that shape plant-pollinator communities. The objectives of this study are to 1) Compare the structure of plant-pollinator networks built on floral visitation and pollen transport data, 2) Evaluate intra-annual variation in plant-pollinator network structure and 3) Evaluate variation in plant-pollinator structure within a single day (i.e. morning vs. evening). Congruence and Temporal Variation of Floral Visitation and Pollen Transport Networks in Southern Appalachia

A polinização pode ser entendida ao nível da comunidade ecológica como uma rede de interacções mutualistas entre dois níveis tróficos, já que a maior das plantas utiliza múltiplos polinizadores e vice-versa. Nos últimos dez anos houve um crescente interesse nas redes de polinização e muitas têm sido estudadas e descritas cobrindo uma ampla variedade geográfica e ecológica. Contudo o estudo dos polinizadores nocturnos ao nível da comunidade, tem sido descurado e praticamente não existem redes nocturnas de polinização descritas na literatura especializada. Os Lepidópteros nocturnos são talvez dos mais comuns polinizadores nocturnos e desempenham um papel muito importante nas comunidades biológicas também como presas e herbívoros. Neste estudo descrevem-se dois tipos de redes de polinização: transferência de pólen e visitação floral; também se identificam alguns lepidópteros polinizadores nocturnos e constrói-se a primeira rede nocturna planta - polinizador para Portugal. As propriedades das redes de polinização estudadas revelaram um valor abaixo do esperado para o aninhamento ponderado e um elevado número de ligações por espécies, o que se reflecte nos valores elevados da diversidade e regularidade das interacções. O grau de especialização é elevado no caso da rede de transferência de polén mas muito baixo no caso da rede de visitação floral. A comprensão da ecologia das borboletas nocturnas é muito importante para a sua conservação e também para a preservação da polinização enquanto serviço dos ecossistemas; ABSTRACT:Pollination can be viewed at the level of an entire ecological community as a network of mutualistic interactions between two trophic levels as most plants utilise multiple pollinators and vice versa. Over the last ten years there has been growing interest in pollination networks and pollination webs have been studied covering a variety of geographical and ecological settings. However, nocturnal pollination as a community-level phenomenon has been overlooked and there are almost no published nocturnal pollination networks. Moths are probably the most common nocturnal pollinators and they play a significant role in many communities as they are also herbivores and prey. In this study two types of networks have been described: pollen transfer and flower visitation, nocturnal Lepidoptera pollinators have been identified and the construction of Portugal´s first nocturnal plant-pollinator network has been described. The main properties studied revealed a lower nestedness than expected when compared with other pollination networks, high number of interactions between species reflected on the high values of interaction evenness and interaction diversity; specialization was high for pollen transfer network and low for flower visitation network. Understanding the ecology of moths is important for the conservation of moth and ecosystem services of pollination.

Whether species interactions are static or change over time has wide-reaching ecological and evolutionary consequences. However, species interaction networks are typically constructed from temporally aggregated interaction data, thereby implicitly assuming that interactions are fixed. This approach has advanced our understanding of communities, but it obscures the timescale at which interactions form (or dissolve) and the drivers and consequences of such dynamics. We address this knowledge gap by quantifying the within-season turnover of plant-pollinator interactions from weekly censuses across 3years in a subalpine ecosystem. Week-to-week turnover of interactions (1) was high, (2) followed a consistent seasonal progression in all years of study and (3) was dominated by interaction rewiring (the reassembly of interactions among species). Simulation models revealed that species' phenologies and relative abundances constrained both total interaction turnover and rewiring. Our findings reveal the diversity of species interactions that may be missed when the temporal dynamics of networks are ignored.

Phenotypic plasticity plays an important role in organisms’ adaptability to environmental change such as global warming caused by greenhouse-gas emissions. One plastic response to increased temperatures is for organisms to shift their phenology. It is of great concern that the phenologies of interacting species, such as plants and pollinators, may be shifting at different rates, causing temporal mismatches, which for plants can lead to unsuccessful reproduction. The “reproductive assurance hypothesis” states that plants capable of self-pollination should be under high selection to employ this as their main reproductive strategy in the event of pollinator scarcity to ensure reproduction, and consequently invest less in attracting pollinators. This study examines how soil warming in the Hengill geothermal area in Iceland affects the flowering phenology, reproductive strategy and investment in attractiveness to pollinators in the self-compatible herb Cerastium fontanum (Caryophyllaceae), when grown in a common garden in Stockholm, Sweden. Previous research showed that C. fontanum from warmed soils flowered earlier in situ than plants from colder soils, and later when grown in a common environment. In this study, C. fontanum plants collected along a temperature gradient followed the same counter-gradient pattern, where plants from warmer soils flowered later than plants from colder soils. Soil temperature at site of origin positively affected flower number but had no effect on flower size, seed production from autogamous self-pollination or visitation rate. Based on my findings it does not appear that C. fontanum, despite having an earlier flowering phenology in situ, is under any selection to alter its reproductive strategy or investment in attractiveness to pollinators when grown in a common temperature, and therefore it seems unlikely that plants are experiencing a temporal mismatch with insect pollinators. However, it would be worthwhile to conduct a similar experiment in Iceland to better understand how an earlier flowering affects pollination systems.

Parmi les polluants présents dans la troposphère, l’ozone (O3) est probablement l’un des plus stressant pour les organismes, du fait de son fort potentiel oxydant. Par exemple, de fortes concentrations d’O3 ([O3]) peuvent affecter l’émission des composés organiques volatils (COVs) permettant aux plantes de communiquer avec leur environnement. De plus, l’O3 peut réagir avec ces COVs dans l’atmosphère pour créer de nouvelles molécules, modifiant ainsi le signal chimique émis par les plantes. Or, ce signal est déterminant dans les interactions plantes-insectes. De nombreuses études ont montré les effets de l’O3 sur les parties végétatives des plantes mais très peu se sont intéressées aux parties reproductives, généralement responsables de l’attraction des pollinisateurs. L’objectif de cette thèse est donc d’améliorer nos connaissances sur l’effet de l’O3 dans les étapes de la communication chimique plantes-pollinisateurs, à savoir (i) l’émission par la plante des COVs floraux, (ii) le signal chimique lors de son transport dans l’atmosphère et (iii) la reconnaissance de ce signal par les pollinisateurs.En Méditerranée, les interactions entre le figuier méditerranéen, Ficus carica (Moraceae), et son pollinisateur très spécifique, Blastophaga psenes (Agaonidae), et entre la lavande vraie, Lavandula angustifolia (Lamiaceae) et son pollinisateur très généraliste l’abeille domestique, Apis mellifera (Apidae), sont les deux modèles d’études emblématiques choisis pour répondre aux objectifs de cette thèse, de par leur degré de spécificité, et la fréquence et l’intensité des pics de pollution à l’O3 dans cette région.Ces travaux de thèse ont combiné des études descriptives et expérimentales afin de déterminer (i) le rythme journalier d’émission des COVs chez la lavande et le figuier, (ii) les variations in natura d’émission des COVs floraux de figuiers exposés de façon chronique ou ponctuelle à une pollution à l’O3 et à d’autres facteurs du changement climatique, (iii) la réponse des deux espèces exposées, en conditions contrôlées, à un pic de pollution à l’O3 en terme d’émission de leurs COVs floraux, (iv) la réaction de l’O3 avec les COVs floraux dans une atmosphère contrôlée et (v) les conséquences de ces deux effets sur l’attraction de leurs pollinisateurs.Les résultats mettent en évidence (i) pour les deux modèles, un rythme d’émission de COVs a priori corrélé à l’intensité lumineuse mais avec différents pics d’émission dans la journée selon les COVs ; (ii) pour le figuier, une variation saisonnière très marquée de l’émission des COVs floraux in natura, en lien avec la température, la sécheresse et les pollutions chroniques et ponctuelles à l’O3 ; (iii) qu’une exposition en conditions contrôlées des deux espèces pendant 5 h à 200 ppb d’O3 ([O3] maximale répertoriée dans les 15 dernières années en méditerranée) n’a pas d’effets immédiats sur l’émission de leurs COVs floraux, mais que (iv) ces COVs seuls exposés à différentes [O3] réagissent différentiellement avec l’O3 pour former de nouvelles molécules, ceci faisant varier les proportions de COVs dans le mélange dès 40 ppb d’O3, et enfin, (v) chez le figuier, que ces variations de COVs inhibent l’attraction du pollinisateur. Cette étude a mis en évidence des sources de variations dans l’émission des COVs floraux chez les deux espèces modèles mais a également permis d’avoir une vision intégrative de l’effet d’un pic de pollution à l’O3 sur la concentration des COVs autour de ces plantes. Plus généralement, ces travaux de thèse soulignent l’importance d’étudier les facteurs du changement climatique co-occurant in natura, notamment les effets de la concentration de différents polluants atmosphériques, sur la communication chimique dans différentes interactions plantes-pollinisateurs afin de mettre en place des mesures de protection de ces interactions face aux changements environnementaux actuels et futurs
Among the pollutants present in the troposphere, ozone (O3) is probably one of the most stressful for organisms, owing to its strong oxidizing potential. For example, high concentrations of O3 ([O3]) can affect the emission of volatile organic compounds (VOCs) that allow plants to communicate with their environment. Moreover, O3 can react with these VOCs in the atmosphere to create new molecules, thus degrading the chemical signals upon which plant-insect interactions, including plant-pollinator interactions, depend. Many studies have shown the effects of O3 on the vegetative parts of plants but very few have studied their effects on their reproductive parts, which are generally responsible for the attraction of pollinators. This work therefore aims to provide knowledge on the effect of O3 in plant-pollinator chemical communication, namely, its effects on (i) the emission of floral VOCs by the plant, (ii) the chemical signal during its transport in the atmosphere and (iii) the recognition of this signal by pollinators.In the Mediterranean region, the interactions between the Mediterranean fig tree, Ficus carica (Moraceae), and its specific pollinator, Blastophaga psenes (Agaonidae), and between the true lavender, Lavandula angustifolia (Lamiaceae), and its generalist pollinator, the honeybee, Apis mellifera (Apidae), are the two emblematic study models chosen to meet the objectives of this dissertation, owing to their specificity and to the frequency and intensity of O3 pollution peaks in this region.This work combined descriptive and experimental studies to determine (i) the daily rate of VOCs emission from flowering plants, (ii) the in natura variation in emission of floral VOCs from fig trees exposed chronically or punctually to O3 pollution and other variables affected by climate change, (iii) the response of plants exposed under controlled conditions to a peak of O3 pollution, in terms of their emission of floral VOCs, (iv) the reaction of O3 with floral VOCs in a controlled atmosphere, and (v) the consequences of these two effects on the attraction of pollinators.The results show that (i) for both models, VOCs emission is correlated with light intensity but also shows different emission peaks during the day, depending on identity of the VOCs; (ii) for F. carica, there is marked seasonal variation in the emission of VOCs in natura, with light intensity, temperature, drought and chronic and acute source of O3 pollution responsible for variations in the emission of floral VOCs; (iii) for both species, exposure under controlled conditions for 5h to 200 ppb O3 (maximum ([O3] recorded in the last 15 years in the Mediterranean region) has no immediate effect on emission of floral VOCs, but (iv) floral VOCs alone exposed to different [O3] react differentially with the pollutant to form new molecules, thus modifying the proportions of VOCs in the mixture at [O3] as low as 40 ppb, and finally, (v) in F. carica, these modifications of VOCs significantly inhibit the attraction of the specific pollinator. This study highlights sources of variation in floral VOC emission in the two model species but also provides an integrative view of the effect of acute exposure to high [O3] on the concentration of VOCs around these plants. Behavioral tests with different pollinators are now essential to characterize the resilience of these interactions to the [O3]-induced variations in VOCs highlighted in this study. More generally, this work points to the importance of studying factors of climate change co-occurring in natura, including the effects of the concentrations of different air pollutants, on chemical communication in different plant-pollinator interactions in order to define measures to protect these interactions in the face of current and future environmental changes

Thesis (PhD(Agric) (Conservation Ecology and Entomology))--University of Stellenbosch, 2010.
ENGLISH ABSTRACT: See full text document for abstract
AFRIKAANSE OPSOMMING: sien volteks dokument vir die opsomming

Kyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第21176号
人博第848号
新制||人||203(附属図書館)
29||人博||848(吉田南総合図書館)
京都大学大学院人間・環境学研究科相関環境学専攻
(主査)教授 加藤 眞, 教授 市岡 孝朗, 教授 瀬戸口 浩彰
学位規則第4条第1項該当

Várias podem ser as causas da variação local no sucesso reprodutivo de espécies vegetais, sendo a disponibilidade de recursos abióticos, herbivoria, polinização e dispersão de sementes comumente consideradas. Em espécies distílicas, a variação na disponibilidade de recursos abióticos pode determinar diferenças na quantidade e no período de produção das estruturas reprodutivas, e estas por sua vez podem influenciar a interação planta polinizador, modulando o comportamento de forrageio de visitantes florais. Este trabalho teve como objetivos verificar como alguns fatores poderiam determinar variação na fenologia e no sucesso reprodutivo de Psychotria suterella, uma espécie arbórea distílica comum em florestas no sudeste do Brasil. Os fatores experimentalmente investigados foram água, luz, nutrientes inorgânicos e superfície foliar. Além disto, investigamos a resposta de abelhas Bombus, B. brasiliensis e B. morio, à disponibilidade de recursos florais em quatro escalas espaciais. A variação na oferta de recursos não afetou o padrão temporal sincrônico de emissão de botões e desenvolvimento de flores dos tipos florais de P. suterella, mas condicionou alterações na quantidade das estruturas reprodutivas produzidas de forma distinta em cada tipo floral. Plantas com morfologia floral longistila parecem estar se reproduzindo sob condições ambientais limitantes, em função de responderem positivamente ao aumento na disponibilidade de recursos, enquanto plantas com morfologia floral brevistila parecem estar melhor adaptadas às condições ambientais, uma vez que responderam negativamente a todos os tratamentos. Respostas fisiológicas singulares parecem ser as responsáveis por essas diferenças. Não houve variação no número de flores, energia produzida no néctar das flores e freqüência de visitas a flores e plantas para os tipos florais de P. suterella. A oferta de energia por flor e a freqüência de visitas por flor variaram entre plantas. Bombus morio e Bombus brasiliensis responderam à variação na disponibilidade de recursos florais de P. suterella em escala espacias menores que 5m, visitando com mais freqüência plantas com maior oferta de energia, independente da disponibilidade energética na vizinhança. Porém, a freqüência de visitas média por flor não apresentou relação com a quantidade de recursos florais nas plantas, e não foi influenciada pela densidade de energia nas demais escalas, fato que deve estar relacionado à grande variação na produção de néctar entre as flores dentro de uma mesma planta.
Several factors might cause intrapopulational variation in plant reproductive success, being often mentioned abiotic resource availability, herbivory, pollination and frugivory as possible factors. In distylous species, the variation on abiotic resources availability can determine differences in quantity as well as in the moment of emisssion of reproductive structures. Those structures might influence the plant-pollinator interaction, modeling foraging behaviour of floral visitors. The aims of this study were to identify how variation in some abiotic resources change the phenology and reproductive success of Psychotria suterella, a common distylous species from Brazilian southeastern forests. We experimentally changed the amounts of light, water, inorganic nutrients and foliar surface. In addition, we measured the frequency of Bombus, B. brasiliensis and B. morio, in relation to floral density at four spatial scales. The variation in abiotic resources availability did not change the temporal pattern of flowering in both, pin and thrum morphs, although bud and flower number was different. Pin plants seemed to be under restrict environmental conditions because the addition of resources increased the number of reproductive structures. On the other hand, any alteration in environmental resources affected negativelly thrum plants. We did not register variation in flower number, energy production in nectar, plant and flower visitation rates for both P. suterella floral morphs. Energy supply per flower and flower visitation rates varied among plants. Bombus morio and Bombus brasiliensis responded to availabitity of floral resources in spatial scales smaller than five meters, visiting more frequently plants with more energy reward regardless of neighbourhood energetic availability. The flower visitation rate was not related to flower resource availability in P. suterella plants. This result might be determined by the high variation in flower energy production within plant.

Pervasive growth in industrialization and advances in technology now exposes much of the world to anthropogenic night light and noise (ANLN), which pose a global environmental challenge in terrestrial environments. An estimated one-tenth of the planet’s land area experiences artificial light at night — and that rises to 23% if skyglow is included. Moreover, anthropogenic noise is associated with urban development and transportation networks, as the ecological impact of roads alone is estimated to affect one-fifth of the total land cover of the United States and is increasing in space and intensity. Existing research involving impacts of light or noise has primarily focused on a single sensory stressor and single species; yet, little information is known about how different sources of sensory stressors impact the relationships within tightly-knit and complex systems, such as within plant-pollinator communities. Furthermore, ANLN often co-occur, yet little is known about how co-exposure to these stressors influences wildlife, nor the extent and scale of how these stressors impact ecological processes and patterns. In Chapter 1, we had two aims: to investigate species-specific responses to artificial night light, anthropogenic noise, and the interaction between the two by using spatially-explicit models to model changes in abundance of 140 of the most prevalent overwintering bird species across North America, and to identify functional traits and contexts that explain variation in species-specific responses to ANLN stressors with phylogenetically-informed models. We found species that responded to noise exposure generally decreased in abundance, and the interaction with light resulted in negative synergistic responses that exacerbated the negative influence of noise among many species. Moreover, the interaction revealed negative emergent responses of species that only reacted when both ANLN were presented in combination. The functional trait that was the most indicative of avian response to ANLN was habitat preference. Specifically, species that occupy closed habitat were less tolerant of both sensory stressors compared to those that occupy open habitat. Species-specific responses to ANLN are context-dependent; thus, knowing the information that regulates when, where, how, and why sensory pollutants influence species will help management efforts effectively mitigate these anthropogenic stressors on the natural environment. In Chapter 2, using field-placed light manipulations at sites exposed to a gradient of skyglow, we investigated the influence of direct and indirect light on the yucca-yucca moth mutualism by quantifying chaparral yucca (Hesperoyucca whipplei) fruit set and the obligate moth (Tegeticula maculata maculata) larval density per fruit. Although many diurnal insects are thought to exhibit minimal phototaxis, we show that direct light attracted adult moths and incited higher pollination activity, resulting in an increase in fruit set. However, larval recruitment decreased with elevated light exposure and the effect was strongest for plants exposed to light levels exceeding natural moonlit conditions (> 0.5 lux). Contrarily, increases in ambient skyglow resulted in an increase in both fruit set and larva counts. Our results suggest that plant-pollinator communities may respond in complicated ways to different sources of light, such that novel selection pressures of direct and indirect light have the potential to benefit or disrupt networks within complex diurnal plant-pollinator communities, and ultimately alter the biodiversity reliant on these systems. By analyzing pervasive stressors across a continental-wide scale, we revealed considerable heterogeneity in avian responses to light and noise alone, as well as the interaction between them. Based on overall responses to the interaction between light v and noise, we suggest management efforts should focus on ameliorating excessive noise for overwintering bird species, which should decrease the impact from synergistic responses, as well as the negative impact from noise alone. There is still much to learn about responses to these stressors and smaller-scale studies should take our approach of systematically assessing interaction responses to ANLN. Moreover, our small-scale study revealed both local sources of direct light and skyglow impact the recruitment for both yucca moths and their reciprocal plant hosts. However, it is still unknown if or why other diurnal pollinators experience positive phototaxis, and whether direct lighting influences the physiology, behavior, or multiple factors relating to reproduction and fitness. Correspondingly, it is unknown if the novel selection pressures of direct and indirect light are disrupting complex diurnal plant-pollinator communities. Future research on artificial night light will need to investigate the intricate responses of diurnal pollinators to both direct and indirect light that will identify concrete mechanisms relating to physiological or behavioral susceptibility and inform predictions on how wide-spread communities will shift with this global driver of emerging change.

Les mécanismes à l'origine de la mise en place de l'isolement reproducteur sont relativement peu étudiés dans les radiations adaptatives insulaires. Selon la théorie de la spéciation écologique, l'isolement reproducteur résulte de la sélection divergente agissant sur des populations écologiquement différentes. Par leurs caractéristiques uniques, les îles océaniques constituent des systèmes idéals pour étudier le rôle des facteurs écologiques dans la diversification des lignées endémiques. Le rôle de l'habitat et des pollinisateurs dans la restriction des flux géniques inter et intraspécifique est examiné chez le faham (Jumellea rossii et J. fragrans), une orchidée endémique des Mascareignes. Pour ce faire, les patrons de différenciation phénotypique (traits floraux morphologiques et chimiques), environnementale (habitat, altitude, climat) et génétique (microsatellites nucléaires) ont été confrontés. À l'échelle intraspécifique, les résultats montrent que les flux de gènes sont principalement limités par les différences environnementales entre habitats sans rôle évident des pollinisateurs. A l'échelle interspécifique, outre les variations d'habitat, le changement de pollinisateur semble expliquer l'absence de flux de gènes. Dans le cadre du continuum de spéciation chez le faham, l'isolement reproducteur évoluerait en premier lieu en réponse à l'adaptation aux différents habitats, puis serait renforcé par l'adaptation à différents pollinisateurs. La révision de la taxinomie du clade et les priorités en terme de conservation sont également discutées
Mechanisms responsible for the establishment of reproductive isolation are little studied in island adaptive radiations. According to the theory of ecological speciation, reproductive isolation results from the ecologically-based divergent selection. By their unique characteristics, oceanic islands are ideal systems to study the role of ecological factors in the diversification of endemic lineages. This study focuses on the role of habitat and pollinators in restricting inter and intraspecific gene flow between populations of faham (Jumellea spp.), an orchid endemic to Mascarene Islands. To do this, patterns of phenotypic differentiation (floral traits), environmental differentiation (habitat, altitude, climate) and genetic differentiation (nuclear microsatellites) were compared. At the intraspecific level, the results show that gene flow restriction is mainly due to the colonization of different habitat types with no obvious role of pollinators. At the interspecific level, in addition to the role of habitat, pollinator shift seems to explain effective complete reproductive isolation. By placing these results into the continuum of speciation, it appears that reproductive isolation evolve initially in response to adaptation to different habitats and, in a second phase, would be enhanced by pollinator-driven divergent selection. Operationally, this study reviews the taxonomy of faham and proposes to define management units and priorities in terms of conservation

Le déclin de la biodiversité et son impact sur le fonctionnement des écosystèmes sont un enjeu majeur du XXIème siècle. L’agriculture intensive est aujourd’hui considérée comme l’un des facteurs responsables de ce déclin, suscitant une volonté sociétale pour une transition vers l’agroécologie. Celle-ci vise à intégrer les fonctions écologiques dans la production des biens agricoles. Les prairies permanentes sont au cœur de ces enjeux, étant à la fois essentielles pour l’alimentation du bétail, tout en pouvant abriter une forte biodiversité. L'intensification des pratiques agricoles peut modifier les communautés de plantes et de pollinisateurs et leurs interactions plantes-pollinisateurs. Actuellement, les mécanismes expliquant ces changements sont peu étudiés, encore moins avec une approche utilisant les traits fonctionnels comme celle que nous proposons dans cette thèse. Les objectifs de cette thèse sont : 1) d’étudier l’effet de l’intensification agricole locale sur la diversité fonctionnelle des traits floraux et les conséquences sur la fonction de pollinisation ; 2) d’étudier les relations entre diversité des traits floraux et diversités taxonomique et fonctionnelle des pollinisateurs ; 3) de déterminer si la pilosité et la surface de la face des pollinisateurs sont des bons prédicteurs de la quantité de pollen transporté. Afin d’atteindre ces objectifs, nous avons sélectionné en Moselle 16 prairies permanentes appartenant à un gradient d’intensification agricole. Nous avons mesuré cinq traits floraux appartenant à trois catégories (signal, barrière à l’exploitation, récompense) sur les espèces de plantes de nos communautés. Nous avons constitué des réseaux visuels d’interactions plantes-pollinisateurs en capturant les insectes butineurs le long de transects. Enfin, nous avons mesuré la masse de ces insectes ainsi que la surface et la pilosité de leur face que nous avons relié à la quantité de pollen qu’ils transportaient. Tout d’abord, nous avons montré que la fertilité du sol a une influence significative sur la diversité fonctionnelle des traits floraux mais pas l’intensification agricole. Alors que la fertilité du sol est connue pour influencer la diversité fonctionnelle des traits végétatifs, ces résultats sont les premiers à montrer un effet du sol sur la diversité fonctionnelle des traits floraux, et pourraient avoir comme origine un phénomène d’exclusion compétitive. L’augmentation de la diversité fonctionnelle des traits floraux augmente significativement la fréquence des interactions plantes-pollinisateurs, proxy de la fonction de pollinisation. Ces résultats sont en concordance avec les relations positives attendues entre biodiversité et fonctionnement des écosystèmes. L’augmentation de la diversité fonctionnelle de la production de sucre augmente significativement la richesse taxonomique des pollinisateurs mais pas la diversité fonctionnelle de leur masse corporelle, suggérant l’importance de maximiser la diversité fonctionnelle de la production de sucre pour maintenir une forte diversité taxonomique de pollinisateurs à l’heure où cette dernière connaît un déclin. Enfin, nous avons montré que la quantité de pollen transporté sur la face des pollinisateurs augmente significativement avec la surface et la pilosité de cette partie de leur corps. Ce résultat est une validation de ces deux traits d’effet pour la pollinisation à un ensemble d’espèces de plantes sauvages, là où ils n’étaient partiellement validés que pour quelques espèces de plantes cultivées. Cette thèse apporte donc une perspective unique sur les effets en cascade des facteurs locaux jusqu’à la fonction de pollinisation en prairie permanente
Decline in biodiversity and its impacts on ecosystem functioning are critical issues we are facing in the 21st century. Intensive agriculture is nowadays considered as one of the factors behind this decline, sparking off a societal desire toward an agroecological transition. Agroecology aims at integrating ecological functions into food production processes. Permanent grasslands are at the core of these issues, because of their essential roles in livestock feeding, but also because of their ability to harbor a rich biodiversity. Intensification of agricultural practices can modify plant and pollinator communities, but also interactions between these two trophic levels. Presently, the mechanisms behind these modifications are little studied, and even less with a functional trait-based approach as we propose in this PhD thesis. The goals of this PhD thesis are: 1) to study the effects of local land-use intensification on functional diversity of floral traits and their consequences on pollination function; 2) to study the relationships between functional diversity of floral traits and both taxonomic and functional diversities of pollinators; 3) to determine if hairiness and surface of pollinator face are good predictors of face pollen load. To do so, we selected 16 permanent grasslands belonging to a land-use intensification gradient in Moselle, France. We measured five floral traits belonging to three categories (cue/signal, exploitation barrier, reward) from plant species in the communities we followed. We established visual plant-pollinator interaction networks by catching foraging insects along transects. Finally, we measured insect body mass, as well as the surface and the hairiness of their face which were related to their face pollen load. Firstly, we found a significant effect of soil fertility on functional diversity of floral traits, but no effect of land-use intensification. While soil fertility is already known to influence functional diversity of vegetative traits, our results show for the first time an effect of soil characteristics on functional diversity of floral traits, that could be caused by exclusive competition. Moreover, an increase in functional diversity of floral traits results in an increase in plant-pollinator interaction frequency, a proxy of pollination function. This result is in congruence with the expected positive relationships between biodiversity and ecosystem functioning. We also found that an increase in functional diversity of nectar sugar production increases pollinator taxonomic richness but not functional diversity of their body mass. This result suggests the importance to maximize functional diversity of sugar production to maintain a high taxonomic diversity of pollinators, while pollinators face currently a global decline. Lastly, we showed an increase in face pollen load of pollinators with hairiness as well as surface of this body part, validating these two pollination effect traits for a set of wild plant species, while until now it was only done for a few cultivated plant species. This PhD thesis thus brings a unique perspective of cascading effects from local factors to pollination function in permanent grasslands

Orientador: Leonor Patricia Cerdeira Morellato
Resumo: A visão é o principal sentido utilizado pelos polinizadores para forragear, no qual a cor das flores é a primeira característica de atração. A percepção dos sinais de cores depende da coloração do segundo plano das flores, composto principalmente pelas folhas. Diferenças na composição das espécies e na estrutura da vegetação, e também na sazonalidade climática, podem interferir na cor do segundo plano de folhas em diferentes vegetações e estações, interferindo como os polinizadores percebem a flor. Portanto, a diversidade de cores das flores e os padrões de floração de uma comunidade podem estar relacionados com a composição de polinizadores e condições ambientais. Desta maneira, utilizando comunidades vegetais e considerando o sistema visual das abelhas, nós descrevemos e comparamos a diversidade de cores das flores e seus sinais, dando importância para a cor do segundo plano de folhas em duas vegetações sazonais tropicais e uma vegetação sazonal temperada. Em seguida, para vincular os sinais florais com a sazonalidade, nós analisamos a importância das síndromes de polinização levantadas, o padrão de floração, a influência da cor do segundo plano de folhas no padrão de cor das flores entre as estações. Nós encontramos diferenças na diversidade de cores das flores e confirmamos a influência da coloração do segundo plano de folhas, juntamente com a estrutura da vegetação e a intensidade da sazonalidade nos sinais florais exibidos em diferentes vegetações sazonais, de acordo co... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Vision is the main sense used to forage by pollinators being the flower colour the primary feature of attraction. Colour signals perception depend on the flower background colouration, mainly composed by leaves. Differences in species composition and vegetation structure, and also the seasonality, may change the leaf-background colouration of different vegetations and seasons, interfering how the pollinators perceive a flower. Therefore, flower colour diversity and flowering patterns of a community may be related to the pollinators’ composition and environmental conditions. Using a community level-approach and according to bee visual system, we described and compared the flower colour diversity and the signals of a temperate and two tropical seasonal vegetations, considering their leaf background colouration. Then, to link flower signals to seasonality and using the cerrado sensu stricto as a model of seasonal vegetation, we analysed the importance of the surveyed pollination syndromes, the community flowering pattern, flowering patterns according to the colour of flowers and the influence of seasonal changes in the background colouration in the flower colour signals between seasons. We found differences in flower colour diversity and confirmed the influence of the leaf- background colouration, along with the vegetation structure and seasonality intensity, in flower colour signals displayed in different seasonal vegetations according to the colour vision of bees. Higher value... (Complete abstract click electronic access below)
Mestre

The world-wide intensification of agriculture has led to a decline in species richness due to land use change, isolation, and fragmentation of natural and semi-natural habitats in agricultural and forestry landscapes. As a consequence, there is a current landscape management focus on the importance of green infrastructure to mitigate biodiversity decline and preserve ecosystem functions e.g. pollination services and pest control. Even though intensification in agriculture has been ongoing for several hundreds of years, remnant habitats from earlier management practices may still be remaining with a surprisingly high plant richness. Preserving these habitats could help conserving plant species richness in agricultural landscapes, as well as other organisms that are dependent on plants for food and shelter. In this thesis I focus on two small remnant habitats; midfield islets and borders between managed forest and crop field in southeastern Sweden. In the past, both habitats were included in the grazing system and therefore often still have remnant population of grassland specialist species left today. I have used these two remnant habitats as model habitats to investigate the effect of landscape factors and local factors on species richness of plants, flower morphologies and plants with fleshy fruits. Additively, I analysed the effect of surrounding landscape and local openness on the functions; pollination success, biological pest control of aphids and seed predation on midfield islets. One of my studies showed that spatial distribution and size of the habitat affected plant species richness. Larger habitat size and higher connectivity between habitats increased species richness of plants in the habitats. Openness of the habitats was shown to be an important factor to increase species richness and richness of flower morphologies, both on midfield islets and in forest borders. Even though midfield islets had the highest species and morphology richness, both habitat types are needed for habitat complementary as forest borders have more plants with fleshy fruits and a higher richness of plant species that flowers in spring/early summer. It was also shown that a more complex forest border, not just with gaps in the canopy, but also with high variation in tree stem sizes increases plant species richness in the field layer. The conclusion is that by managing small remnant habitats to remain or become more semi-open and complex in their structure, would increase species richness of plants, grassland specialist species, and flower morphologies. It would also increase some ecosystem functions as seed predation and biologic pest control of aphids are more effective close to trees. If both midfield islets and forest borders would be managed to be semi-open, the area and connectivity of semi-open habitat would increase in the agricultural landscape, which may also improve pollination success as the connectivity between populations has a possibility to increase. Grassland specialist species are clearly abundant in the small remnant habitats. As the decline of semi-natural grasslands is causing a decline in grassland specialists’ species, not only plants, I recommend that small remnant habitats are included in conservation and management plans and strategies to improve habitat availability and connectivity for grassland species in agricultural landscapes.

Research funder Ekoklim. Project:4339602.

At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Manuscript.

Climate change is shifting the seasonal timing of many biological events, and the possibility of non-parallel shifts in different taxa has raised concerns about phenological decoupling of interacting species. My thesis investigates interactions between climate, phenology, and pollination, using the plants and pollinators of Rocky Mountain meadows as a study system. Interannual variation in timing of snowmelt since the 1970s has been associated with changes in the assemblages of concurrently flowering species in these meadows, suggesting that plant species differ in their phenological responses to climate. Differences between plants and pollinators in responsiveness to changing climate could, in principle, cause early-flowering plants to flower too early in warm years, before pollinators are active. In fact, I found only transient evidence for pollinator deficits in one early-flowering species (Mertensia fusiformis), even in an early-snowmelt year. However, the assemblage of pollinators visiting M. fusiformis does change predictably over the season, with likely consequences for selection on floral morphology in years when pollen is limiting. Hence, early- and late-flowering populations may evolve in response to phenology of the pollinator community. Differences between plant and pollinator phenologies appear to be due to generally lower temperature thresholds for development in plants, combined with microclimate differences between the soil and the above-ground nests of some pollinators. Phenological decoupling between plants and pollinators seems possible but unlikely to be catastrophic, since many taxa possess adaptations to temporally variable environments. Nevertheless, for many species, adaptation to novel climates will entail evolutionary change, and species interactions can influence evolutionary trajectories. For species affected by increasing late-summer drought, earlier flowering may be advantageous. However, in laboratory experiments, bumble bees avoid rare, unfamiliar flower types, causing simulated plant populations to fail to adapt to changing conditions. Overall, my work emphasizes the importance of the interplay between species interactions and environmental change.

Dissertação de Mestrado em Ecologia apresentada à Faculdade de Ciências e Tecnologia
O uso crescente de agroquímicos, sobretudo fertilizantes e pesticidas, torna-se cada vez mais um fator preocupante no que toca ao ténue equilíbrio entre estabilidade ecológica e expansão agrícola. Ainda mais quando a expansão de terras agrícolas e intensificação agrícola podem causar um impacto drástico na composição floral e disponibilidade de locais de nidificação e, por sua vez, alterar as interações planta-polinizador. Não são só as flores silvestres que dependem dos polinizadores, mas também as espécies agrícolas, já que uma esmagadora parte das espécies agrícolas são polinizadas pelos insetos e uma disrupção neste mutualismo também poderá causar uma disrupção na produção agrícola. Um aumento de nutrientes disponíveis no solo pode afetar os ecossistemas contíguos, e.g., sistemas de água doce, devido ao runoff de nutrientes, aumentando a eutrofização. Infelizmente, faltam-nos conhecimentos no que diz respeito ao impacto dos fertilizantes no comportamento e saúde de polinizadores. Como tal, o objetivo deste estudo foi avaliar como é que diferentes níveis de azoto (N) e fósforo (P) podem afetar características florais, como a produção de flores, e subsequentemente alterar as taxas de visita e produtividade em espécies agrícolas. As espécies foram selecionadas com base na sua capacidade de reterem azoto, portanto foram usadas espécies fixadoras de azoto (Vicia faba e Phacelia tanacetifolia) e não-fixadoras de azoto (Solanum lycopersicum). Os tratamentos resultaram de um design fatorial, entre três níveis de azoto (N) e dois de fósforo (P). Os resultados indicam que os efeitos dos fertilizantes são específicos das espécies e das doses usadas: em S. lycopersicum, os polinizadores visitaram mais plantas em solos com a dose recomendada de N e P; ao passo que V. faba e P. tanacetifolia não demonstraram diferenças significativas. Também foi demonstrado que a produção de frutos não foi afetada pelas taxas de visita dos polinizadores, apesar da produção de sementes poder potencialmente beneficiar do aumento de polinização. Deste modo, um uso crescente de fertilizantes para obter uma produção ótima poderá não ser a melhor abordagem a ter, já que a produção também vai depender de outros fatores, como a polinização. Para que possamos satisfazer as nossas necessidades alimentares, ao mesmo tempo que se salvaguarda a estabilidade ecológica, é necessário investigar mais como é que os diferentes fatores que envolvem as interações planta-polinizador e a eutrofização interagem nas diferentes espécies agrícolas.
The increased use of agrochemicals, mainly fertilizers and pesticides, is becoming a worrying trend in the precarious balance between ecological stability and agricultural expansion. The increased land use and agricultural intensification can impact drastically floral composition and nesting sites suitability and thus, mediate changes in plant-pollinator interactions. Not only wildflowers depend on pollinators but also crops, being that most of the crop species in the world are pollinated by insects and a disruption in this mutualism can also translate into disruption in crop production. An increase in nutrient availability in the soil can impact adjacent ecosystems, e.g., freshwater ecosystems, due to nutrient runoff, enhancing eutrophication. Unfortunately, there are quite some gaps in the knowledge we currently possess when it comes to fertilizer effects in pollinator behavior and health. Therefore, the objective of this study was to assess how different levels of nitrogen (N) and phosphorus (P) can affect flower characteristics, such as flower production, and subsequently affect pollinator visitation rates and yield in crop species. Crops were selected based on their nitrogen-fixing ability and thus, nitrogen-fixing (Vicia faba and Phacelia tanacetifolia) and non-nitrogen fixing (Solanum lycopersicum) species were used. Treatments consisted in a full factorial design between three levels of N and two levels of P. It was found that fertilizers effects on crops are species-specific and dose-specific: in S. lycopersicum, pollinator visits were higher in plants growing in soils with recommended dosages of N and P; while V. faba and P. tanacetifolia showed no significant differences. It was also found that fruit set was not affected by visitation rates, despite seed set can be potentially benefited from increased pollination. Therefore, increased use of fertilizers for maximum crop production might not be the best approach, as plant yield will also depend on insect visitation. In order to guarantee that our dietary needs are met, while also maintaining ecological stability, we need to further investigate how the different drivers surrounding plant-pollinator interactions and eutrophication act in various crop species.
Outro - Effect of EUtrophication and CLimate on POllinators and ecosystem service provision (EUCLIPO); EUCLIPO project PTDC/BIA-ECO/28360/2017; The project is funded by FCT and European Union via the Lisbon Regional Operational Program 2014/2020 (Lisboa2020).

Several aspects of plant-pollinator interactions are presented in the thesis. It contains a review on the open questions of plant-pollinator interactions from single species to complex networks. The following sections document novel results. Firstly, the conservation of complex pollination networks is addressed through the hierarchy of species' importance. In addition, the habitat requirements and interactions of a threatened rare pollinator species are explored. In the following chapters, the results from manipulative approaches applied in the field to plant-pollinator interactions are presented. The effect of pollinator's population decline on pollinators' foraging for pollen is investigated. Moreover, the way plant species loss impact several aspects of pollinator visitation is presented. Lastly, the impact of species removal on plant-pollinator network topology and on species ability of establishing new interactions is investigated.

Montane meadows comprise less than 5% of the landscape of the western Cascades of Oregon, but they provide habitat for diverse species of plants and pollinators. Little is known about plant-pollinator network structure at these sites. This study quantified plant-pollinator interactions over the summer of 2011, based on six observations of 10 permanent subplots in 15 meadows, stratified by size and isolation. The study examined (1) relationships between richness and abundance of flowers, pollinators, and interactions; (2) distribution of abundance and richness of flowers, pollinators, and interactions with regards to surrounding meadow habitat; (3) change in flower and pollinator abundance over the season; (4) factors associated with the presence of various guilds of pollinators; and (5) the structure of plant-pollinator networks. The study showed that (1) richness of pollinators increased 2x faster than richness of flowers with increased abundance; (2) density of flowers and interactions was positively correlated with meadow size and diversity of pollinators and interactions were both correlated with surrounding habitat at two spatial scales; (3) peak flower abundance coincided with or preceded peaks in pollinator populations; (4) abundance of three guilds of bees exhibited different patterns of association to surrounding habitat and meadow soil moisture corresponding to various dispersal potential and phenology of guild species; and (5) the number of network pairings for plants and pollinators increased with increasing species richness of potential interaction partners and all networks were found to be significantly nested. Results of this study indicate that plant-pollinator networks are complex assemblages of species, in which spatial and temporal patterns of habitat affect species composition and network structure. In particular, flower and pollinator abundance and richness are depressed in small and isolated meadows. Significant nestedness emerged as a pattern of network level organization across the study meadows.
Graduation date: 2013

There is concern that climate change may cause mismatches between timing of flowering and activity of pollinators (phenology). However, concluding that mismatches will occur, and have serious consequences for pollination services, requires assumptions that have not yet been tested. I begin by discussing a set of these assumptions, bringing past research into the context of mismatch. Briefly, the assumptions are that 1) dates of first-flowering or emergence (DFFE) correctly describe phenology (and therefore mismatch); 2) differences in DFFE represent the magnitude of mismatch; 3) advancement of DFFE will be the primary phenological change; 4) shifts will be random and independent for each species; 5) populations of plants and pollinators are “bottom-up” regulated by their mutualistic interactions; 6) all interactions are of similar strength and importance; 7) dispersal, and the spatial context of phenological mismatches can be ignored; and ecological processes including 8) phenotypic plasticity and adaptive evolution of phenology, 9) competition and facilitation, and 10) emergence of novel interactions, will not affect mismatches. I then describe novel experiments, which could help to account for some of these assumptions, clarifying the existence and impacts of mismatches. Next, I present an original field experiment on factors affecting seed set in an alpine meadow in the Coast Range of British Columbia, Canada. I found evidence contradicting the assumption that seed set is primarily limited by pollination. My data highlight the roles of phenology, temperature (degree-days above 15°C, and frost hours), and interactions with pollinators (mutualists) and seed-predators (floral antagonists) in driving patterns of seed set. Seed set of early and late-flowering species responded differently to a 400m elevation gradient, which might be explained by phenology of bumble bees. My data suggest that the consequences of mismatch may be smallest for plants that are fly-pollinated and self-fertile. Non-selfing, bee-pollinated species might be more prone to reproductive limitation through mismatch (affected by snowmelt and cumulative degree-days). Plants that are limited by seed-predators might be negatively affected by warming temperatures with fewer frost hours, and extreme events such as late-season frosts and hail storms can prevent plants from setting seed entirely. Overall, my work emphasizes the importance of complementing theory, data-driven simulations, and meta-analyses with experiments carried out in the field.
Graduate

In present thesis, I treat the topic of impacts of plant-animal interactions, namely herbivory and pollination, on plant life cycle and lifetime fitness. First, I identify the components of the impact of plant-animal interactions: i) interaction frequency; ii) per-interaction effect; iii) sensitivity of the plant's life cycle to the changes in vital rate impacted by the animals. Furthermore, I also classify other causes changing the outcome of a plant-animal interaction into two categories: i) plant's traits; ii) plant's environment. A review of extant literature on the topic revealed that especially the role of plant's environment in changing the outcome of plant-animal interactions is largely understudied and I attempt to reduce this gap in knowledge in the five detailed studies encompassed in this thesis. The detailed studies focus on a model system of Central European wet grasslands and especially on three species typical to it: Succisa pratensis, Achillea millefolium and A. ptarmica. The first two studies examine the effects of environment on frequency of plant- animal interactions. The next two studies are more integrative, one focusing on the impacts of different herbivore groups on the complete life cycle and the other on interaction of herbivory and pollination on plant lifetime fitness....

Plant-pollinator interactions figure as key elements promoting the natural regeneration of terrestrial vegetation, as most plants depend on animals to transfer their gametes between flowers and produce seeds. Bees are the most common pollinators of plants and their interactions with flowers have served as model systems for the study of specialized mutualisms since Darwin's time. While most plants offer nectar as a reward and attract a variety of floral visitors, others produce distinctive types of resources which are sought by particular groups of pollinators. Such associations may involve specialization at the morphological, behavioral, or physiological levels and are especially common in tropical habitats. The interactions between oil-producing flowers of Neotropical Malpighiaceae and oil-collecting bees are an example of a specialized mutualism in which plants offer lipids to attract pollinators that use the resource to build nest cells and feed their offspring. Although several studies have focused on specialized pollination at the species level, their effects on the organization of tropical communities remain largely unexplored. This dissertation aims to help fill this gap through an analysis of the mechanisms of pollinator partitioning in multi-species assemblages of specialists as well as a study of the organization of communities in which they occur. The motivation for pursuing the study of specialized interactions using Neotropical species of Malpighiaceae as a model system is outlined in the first chapter. In Chapter 2, I present an evaluation of the structural properties of a plant-pollinator community from the Cerrado, a seasonal ecosystem that hosts a large diversity of oil flowers. The third chapter analyzes pollinator partitioning and reproductive strategies promoting the coexistence of closely related Malpighiaceae. A possible outcome for the selective pressures imposed by the coexistence of specialists is presented in Chapter 4 by a case study providing evidence for a shift from specialized to generalized pollination in a Neotropical Malpighiaceae species. The last chapter includes reports of active floral oil foraging by males of Tetrapedia and a description of an oil storage structure without precedence among bees and unique to males of this genus suggesting that floral oils may also play a role in bees mating systems.
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