Dissertations / Theses on the topic 'Omnivory'

One of the basic questions of concern in mathematical biology is the long-term survival of each species in a set of populations. This question is particularly puzzling for a natural system with omnivory due to the fact that simple mathematical models of omnivory are prone to species extinction. Omnivory is defined as the consumption of resources from more than one trophic level. In this work, we investigate three omnivory models of increasing complexity. We use the notion of permanent coexistence, or permanence, to study the long-term survival of three interacting species governed by a mixture of competition and predation. We show the permanence of our models under certain parameter restrictions and include the biological interpretations of these parameter restrictions. Sensitivity analysis is used to obtain important information about meaningful parameter data collection. Examples are also given that demonstrate the ubiquity of omnivory in natural systems.
Ph. D.

Publisher version
We utilised stable isotope ratios to assess differences in diet among three indigenous and syntopic rocky shore suspension-feeders (mussels Perna perna, barnacles Tetraclita serrata, and polychaetes Gunnarea gaimardi). We also determined the spatial and temporal variability in the suspension-feeder diets by collecting specimens on two occasions from two regions adjacent to hydrologically distinct river mouths (i.e. one with larger annual freshwater throughput than the other). The results showed that the isotopic niches (used as proxies for trophic niches) of the three species did not overlap and that the barnacles occupied a trophic position (3.4) well above those of the mussels (2) and polychaetes (2.6). We ascribed the interspecific differences primarily to the disparate feeding mechanisms used by the species. Large-scale regional (~50 km) differences in suspension-feeder diets were apparent, but not small-scale (up to a few km north and south of each estuary mouth). The regional differences in diet resulted from the increased availability of estuarine-origin suspended particulate matter (SPM) and zooplankton in the region adjacent to the river with relatively larger freshwater output, although overall incorporation of zooplankton versus mixed SPM into consumer diets was relatively consistent between regions and through time. Temporal shifts in suspension-feeder diets were apparent from stable carbon isotope ratios in the consumers. Our results showcase the measurable effects of regional-scale processes that can alter the food sources for dominant primary consumers in the rocky intertidal, thus potentially affecting entire food webs through bottom-up processes. The clear evidence for trophic niche partitioning offers valuable insights into how potentially strong competitors can coexist.

Thesis (Ph. D.) -- University of Maryland, College Park, 2007.
Thesis research directed by: Entomology. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

The role of omnivores in structuring communities is poorly understood. I studied the effect of two abundant omnivores, grass shrimp (Palaemonetes paludosas) and eastern mosquitofish (Gambusia holbrooki), on periphyton biomass of the Florida Everglades. I performed field experiments to test for consumer top-down and “complex” top-down effects on periphyton biomass. My experiments suggested that shrimp and mosquitofish had consumptive effects on periphyton but in many instances, periphyton wet weight, AFDM, and chlorophyll a increased significantly with shrimp or fish density, suggesting compensation by nutrient regeneration or trophic cascade processes. I propose that characteristic periphyton mat structure and integrity deters herbivory and affects the outcome of the periphyton-consumer interaction. Results from a descriptive study and a laboratory experiment support this hypothesis. Overall, consumption by shrimp and mosquitofish was significant, but coupled with and sometimes compensated by “complex” top-down effects, making these consumers “functional” omnivores.

Insecticidal neonicotinoid seed treatments in agriculture is a common insect pest management strategy. Seed treatments have systemic and residual toxicity, which are effective against target insect pests. However, effects on other arthropod pests is less straightforward. We evaluated the effects of a neonicotinoid seed treatment, thiamethoxam, on two soybean pests, herbivorous two-spotted spider mites (Tetranychus urticae Koch) and an omnivore and facultative predator of spider mite eggs, western flower thrips (Frankliniella occidentalis Pergande). We used greenhouse and laboratory experiments to evaluate thiamethoxam soybean seed treatments on spider mite densities and thrips omnivorous feeding behavior. Our results suggest seed treatment may encourage spider mite reproduction and influence thrips herbivory over egg predation when both resources are available. Implications of this study highlight the use of thiamethoxam soybean seed treatment as a potential contributor to increased spider mite populations, thrips reduced role as spider mite predator, and increased role as herbivorous pest.

Biomanipulation im Sinne einer top-down Steuerung des Nahrungsnetzes wurde in Standgewässern intensiv erforscht und wird als Mittel zur Verbesserung der Wasserqualität bzw. Verringerung der Eutrophierungserscheinungen eingesetzt. Ebenso könnte die Idee der Biomanipulation genutzt werden, um die Eutrophierung in kleinen Fließgewässern zu verringern. Eine Förderung benthischer herbivorer Schlüsselorganismen (z.B. Eintagsfliegenlarven) durch die Reduzierung des Fischfraßdruckes könnte helfen, Algenmassenentwicklungen zu vermeiden. Studien zur Biomanipulation von Nahrungsnetzen in Standgewässern zeigten allerdings eine zunehmende Entwicklung von planktischen invertebraten Räubern bei Abwesenheit planktivorer Fische. Die Bedeutung des Fraßdruckes invertebrater Räuber in fischfreien Fließgewässernahrungsnetzen ist dagegen noch unbekannt. Aufgrund von letalen und subletalen Fischeffekten könnte die Konsumtion räuberischer Invertebraten bei Fischabwesenheit so stark gefördert werden, dass das Ziel der Biomanipulation verfehlt wird. Invertebrate Räuber haben insgesamt einen relativ hohen Anteil an der Biomasse der Benthosgemeinschaft in Fließgewässernahrungsnetzen. Sie könnten somit potentiell einen ähnlichen Fraßdruck wie vertebrate Räuber (z.B. benthivore Fische) auf die unteren trophischen Ebenen ausüben. Auch der Anteil der Omnivorie ist in Fließgewässernahrungsnetzen hoch. Ziel dieser Arbeit war es deshalb, die Bedeutung invertebrater Prädation im Nahrungsnetz eines kleinen Fließgewässers (Gauernitzbach) unter Berücksichtigung der obligaten Räuber sowie des räuberischen Potentials Omnivorer abzuschätzen. Außerdem wurde der Einfluss benthivorer Fische auf die Populationsentwicklung und das Ernährungsverhalten der wichtigsten invertebraten Räuber und Omnivoren untersucht. Dazu wurde ein Bachabschnitt, der mit benthivoren Fischen (Gobio gobio, Barbatula barbatula) besetzt war, mit einem fischfreien Abschnitt über zwei Jahre verglichen. Nach der Identifizierung wichtiger Räuber- und Omnivorenarten anhand ihrer Biomasse und ihrer trophischen Positionen mittels Isotopenanalyse wurde ihr Gesamtfraßdruck abgeschätzt. Invertebrate Prädatoren im Nahrungsnetz des Gauernitzbaches waren Rhyacophila fasciata und Plectrocnemia conspersa (Trichoptera), Isoperla grammatica (Plecoptera) sowie Dugesia gonocephala (Turbellaria). Wichtige Omnivore aufgrund ihrer hohen Biomassen waren Gammarus pulex (Amphipoda) und Hydropsyche spp. (Trichoptera). Anhand eines Mischungsmodells (ISOSOURCE), das auf der Basis der stabilen Isotopensignaturen d13C und d15N die einzelnen Ressourcenanteile einer gemischten Signatur berechnet, konnte das ausgeprägte räuberische Potential der Omnivoren gezeigt werden, da sie einen hohen tierischen Anteil in der Nahrung aufwiesen (20-90 %). Im Nahrungsnetz des Gauernitzbaches waren Omnivore als Räuber damit ebenso bedeutsam wie obligat räuberische Invertebrate. Der Gesamtfraßdruck der invertebraten Räuber und Omnivoren auf die Beuteorganismen (bis 16 g TM m-2 a-1) in der Fischstrecke war höher als der Fraßdruck der benthivoren Fische (~3 g TM m-2 a-1). Dieser Unterschied lag hauptsächlich in höheren täglichen Konsumtionsraten bei ähnlich hohen Biomassen der Invertebraten begründet. Durch die Analyse der stabilen Isotope von Kohlenstoff und Stickstoff konnten die trophischen Beziehungen im Nahrungsnetz des Gauernitzbaches identifiziert werden. Dabei stellten allochthone Kohlenstoffquellen im Frühjahr und Herbst die bedeutendste Ressource für die Primärkonsumenten dar, während autochthone Ressourcen nur im Frühjahr für wenige Herbivore relevant waren. Dies spiegelte sich ebenso in der Nahrung der Omnivoren wider, die neben Organismen hauptsächlich Detritus nutzten. Ebenso zeigten die invertebraten Räuber eine deutliche Abhängigkeit vom allochthonen Kohlenstoff über die Nutzung der Primärkonsumenten. Letale Effekte der Fische auf die räuberischen und omnivoren Populationen im Gauernitzbach fanden hauptsächlich in Abhängigkeit von den bewohnten Habitaten statt. Die Pool-Arten (P. conspersa, D. gonocephala, G. pulex) entwickelten geringere Biomassen in der Fischstrecke, während die Biomassen riffle-bewohnender Invertebraten (R. fasciata, I. grammatica, Hydropsyche spp.) nicht deutlich reduziert wurden. Dabei waren allerdings meist hohe Biomassen in der Fischstrecke weniger stark ausgeprägt als in der fischfreien Strecke. Die Adulten der untersuchten Arten wurden oft stärker letal beeinflusst als die Juvenilstadien. So war die Emergenzproduktion der räuberischen Köcherfliegen und die Abundanz großer und eiertragender Weibchen von G. pulex in der Fischstrecke deutlich verringert. Subletale Effekte der Fische traten im Gauernitzbach in Abhängigkeit von den Ernährungstypen auf. Während die adulten räuberischen Köcherfliegenarten R. fasciata und P. conspersa keine negative Beeinflussung der Fitness und Größe zeigten, emergierte die omnivore Köcherfliege H. instabilis in der Fischstrecke kleiner als in der fischfreien. Außerdem unterschieden sich die Antworten der omnivoren Arten vermutlich aufgrund ihrer unterschiedlichen Lebenszyklen. G. pulex zeigte als ausschließlich aquatisch lebende Art keine subletalen Kosten (unveränderte Fitness) bei Fischanwesenheit wie dies für die omnivore merolimnische Insektenart H. instabilis beobachtet wurde. Die mittlere Fitness der Populationen (gemessen an der Eiproduktion pro Zeit- und Flächeneinheit) war für alle untersuchten invertebraten Räuber und Omnivoren bei Fischanwesenheit deutlich geringer als in der fischfreien Strecke. Für die Räuber (R. fasciata, P. conspersa) und G. pulex waren vermutlich letale Fischeffekte für den geringen Reproduktionserfolg verantwortlich. Dagegen wurde die Fitness der Population von H. instabilis durch die Kombination aus der geringeren individuellen Körpergröße (subletal) und den schwachen letalen Effekten auf die Emergenz reduziert. Der Einfluss der Fische auf die räuberischen Larven von R. fasciata und P. conspersa resultierte in einem Wechsel der Beutezusammensetzung, nicht in der Reduzierung der täglichen Fraßaktivität. Dies war vermutlich auf eine Aktivitätsänderung des Räubers R. fasciata bzw. auf die veränderte Beuteverfügbarkeit für P. conspersa unter Fischeinfluss zurückzuführen. Eine grundsätzliche Verringerung der Fraßaktivität oder der tierischen Anteile in der Nahrung der omnivoren Arten unter dem Einfluss benthivorer Fische wurde nicht festgestellt. Dagegen änderten sich die Relationen der Ressourcen Omnivorer zueinander, so konnte in der fischfreien Strecke eine flexiblere Ressourcennutzung nachgewiesen werden. Die jährliche Gesamtkonsumtion der räuberischen und omnivoren Invertebraten wurde durch die Anwesenheit der benthivoren Fische um 20-50 % reduziert, wofür hauptsächlich fischinduzierte Biomasseänderungen verantwortlich waren. In der fischfreien Strecke konnte dagegen die erhöhte Konsumtion der Invertebraten den fehlenden Fischfraßdruck mehr als kompensieren. Allerdings änderte sich die beutespezifische Konsumtion der Räuber in der fischfreien Strecke durch den verhaltensinduzierten Wechsel in der Beutezusammensetzung. Damit fand ein erhöhter Fraßdruck auf detritusfressende Arten (z.B. Diptera) statt, während die vermuteten Schlüsselarten einer potentiellen Biomanipulation (grazende Eintagsfliegen) in der fischfreien Strecke relativ unbeeinflusst blieben. Da die invertebrate Prädation in Fließgewässern sehr bedeutend sein kann, ist Biomanipulation nur unter Berücksichtigung aller Populationen räuberischer Invertebraten möglich. Nur durch Einstellung einer optimalen (relativ hohen) Biomasse geeigneter benthivorer Fischarten kann eine ausreichende Hemmung der invertebraten Räuber erreicht werden, so dass grazende Arten indirekt profitieren
Biomanipulation (top-down control of the food webs) in lakes was intensively studied and can today be regarded as an important tool for improvement of the water quality and eutrophication. Similarly, the idea of biomanipulation can be used to reduce eutrophication phenomena in streams. The enhancement of benthic herbivorous key species (e.g. mayflies) by reduction of fish predation pressure could prevent exploding benthic algae biomass. Studies dealing with trophic cascades in lakes suggested that biomass of planktic invertebrate predators is increasing in the absence of planktivorous fish. But until now the importance of invertebrate predation pressure in fishless stream food webs is hardly known. Due to lethal and sublethal fish effects the consumption of predatory invertebrates could be enhanced by the absence of fish to such an extent that biomanipulation could be off target. In general, the proportion of invertebrate predators to the biomass of the benthic community in stream food webs is relatively high. Therefore, invertebrate predation on benthic prey can be as important as vertebrate predation (e.g. by benthivorous fish). Furthermore, omnivory occurs frequently in streams. Therefore, the aim of this thesis was to assess the importance of invertebrate predation in a food web of a small stream (Gauernitzbach) including the obligatory predators as well as the predatory potential of omnivores. Furthermore, the impact of benthivorous fish on population dynamics and feeding behaviour of the most important predators and omnivores was studied. Therefore, a reach stocked with benthivorous fish (Gobio gobio, Barbatula barbatula) was compared with an upstream fishless reach over a two-year period. After identification of important predators and omnivores based on their biomass and trophic position by stable isotope analyses their total consumption was estimated. Rhyacophila fasciata and Plectrocnemia conspersa (Trichoptera), Isoperla grammatica (Plecoptera) as well as Dugesia gonocephala (Turbellaria) were the invertebrate predators in the food web of Gauernitzbach. Because of their high biomasses the most important omnivores were Gammarus pulex (Amphipoda) and Hydropsyche spp. (Trichoptera). Using a mixing model (ISOSOURCE) that estimates the proportions of single resources on a mixed signature on the basis of the stable 13C and 15N isotopes, the predatory potential of both omnivores was pronounced by a high animal food proportion (20-90%). In this stream food web the predation impact of omnivores was comparable to this of obligatory predacous invertebrates. The total invertebrate predation pressure (up to 16 g TM m-2 a-1) in the fish reach was higher than the vertebrate predation pressure (~3 g TM m-2 a-1) mainly caused by the higher daily consumption rates and similar biomass compared to fish. Using stable isotope analyses of carbon and nitrogen the trophic pathways in the food web of Gauernitzbach could be identified. The most important resources for primary consumers in spring and autumn were allochthonous carbon sources. Autochtnonous carbon sources were only utilized by a few herbivores in spring. This was also reflected in the food of omnivores which assimilated mainly detritus beside animal material. Similarly, the predators depended distinctly on the allochthonous pathway by feeding primary consumers. Lethal fish effects on the predatory and omnivorous invertebrate populations were mainly depended on their preferred habitats. Pool-dwelling species (P. conspersa, D. gonocephala, G. pulex) showed decreased biomass in the presence of fish. Contrary, the biomass of riffle-dwelling invertebrates (R. fasciata, I. grammatica, Hydropsyche spp.) was not significantly reduced in the fish reach. Thereby, the highest biomass values in the fish reach could not reach the same level as in the fishless reach. Adults of the investigated species were influenced more lethal than the young stages. Hence, the emergence production of the predatory caddisflies and the abundance of the biggest and gravid females of G. pulex were reduced in the fish reach. Sublethal fish effects existed in dependence on the feeding groups of the invertebrates in Gauernitzbach. Whereas the adult predatory caddisflies R. fasciata and P. conspersa did not show disadvantages in fitness and size, the omnivorous caddisfly H. instabilis emerged with smaller size in the fish reach than in the fishless reach. Different responses of both omnivorous species were observed because of their different life cycles. The exclusively aquatic living G. pulex was not influenced sublethal by fish as the merolimnic insect species H. instabilis. The average fitness of population (measured as egg production per unit time and space) of the studied invertebrate predators and omnivores was distinctly reduced in the fish reach compared to the fishless reach. Probably, lethal fish effects were mainly responsible for the low reproductive success of the predatory species (R. fasciata, P. conspersa) and G. pulex. In contrast, the reduction of population fitness of H. instabilis was caused by the reduced individual adult size (sublethal effect) in combination with the weak lethal effect on emergence. The impact of fish on the feeding behaviour of the predatory larvae of R. fasciata and P. conspersa resulted in a switched prey composition, whereas a reduction in the daily feeding activity was not observed. That was supposed because of changes in the activity pattern by the predator R. fasciata or the changed prey availability for P. conspersa in the fish reach. A general reduction in feeding activity or animal food proportion of the omnivores was not assessed in the presence of fish. In contrast, the relations between the resources switched to a more variable utilisation in the fishless reach. The annual total consumption of invertebrate predators and omnivores was decreased by 20-50% in the fish reach, mainly caused by fish induced biomass reduction. The missing fish consumption could be at least balanced by higher invertebrate consumption in the fishless reach. Contrary, the prey specific consumption of invertebrate predators changed by behavioural-induced switch in the prey composition between the stream reaches. Therefore, a higher predation pressure on detritus feeding species (e.g Diptera) was found in the fishless reach, but not on the supposed key species of the potential biomanipulation (e.g. grazing mayflies). Due to the high importance of invertebrate predation in stream food webs, the aim of biomanipulation can only be reached by considering the populations of predatory invertebrates. Controlling the biomass of suitable benthivorous fish to an optimum (relatively high) level could sufficiently reduce the impact of invertebrate predators leading to an indirect enhancement of grazing species

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2018-04-12T13:21:43Z No. of bitstreams: 1 PDF - Maysa Pereira Tomé.pdf: 11904267 bytes, checksum: b0b5c1332accda7862833abc1ec7b0e8 (MD5)
Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2018-04-23T20:28:05Z (GMT) No. of bitstreams: 1 PDF - Maysa Pereira Tomé.pdf: 11904267 bytes, checksum: b0b5c1332accda7862833abc1ec7b0e8 (MD5)
Made available in DSpace on 2018-04-23T20:28:05Z (GMT). No. of bitstreams: 1 PDF - Maysa Pereira Tomé.pdf: 11904267 bytes, checksum: b0b5c1332accda7862833abc1ec7b0e8 (MD5) Previous issue date: 2018-02-02
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The Dermaptera order is composed by species considered generalist predators, much used in the biological control of several insect pests. The earwigs, Euborellia annulipes (Dermaptera: Anisolabididae) is an omnivorous species, considered an important controlling agent for larvae and pupae of boll weevil and other insect pests of economic importance. However, a few studies claim that this earwig is predominantly phytophagous, with the potential to become a secondary pest in protected crops. Therefore, the objective of this research was to determine the development and survival of E. annulipes with cotton leaves and/or cotton boll weevil larvae. The experiment was conducted at the Entomology Laboratory of the Embrapa Cotton, municipality of Campina Grande, Paraiba, Brazil. The experimental design was completely random, with three treatments and 50 replicates. The treatments consisted of nymphs of the earwigs fed with: (1) disc of cotton leaves and water (vegetable diet); (2) third instar larvae of boll weevil and water (animal diet) and (3) larvae of boll weevil, cotton leaf and water (mixed diet). The nymphs of the earwigs were fed 'ad libitum' with one of the three diets mentioned and kept in climatic chambers of type B.O.D. at 25 °C, relative humidity of the 60 ± 10% and 12 hours of the photoperiod until the end of the bioassay. Subsequently, adults of the earwigs were sexed, grouped into couples for copulation and after mating individualized in plastic pots and fed with the three types of diet mentioned and kept in a climatic chamber until death. The survival and duration of each instar and nymphal stage of E. annulipes were determined by recording the interval in days between ecdises, as well as sexual ratio, adult longevity and the following morphometric data: body length, number of antenomers and abdominal segments. The results obtained in this research indicate that only the consumption of vegetable diet by E. annulipes is not enough to meet the nutritional requirements of its immature stages. Nymphs of early stages of development prefer to feed on an animal diet, while the more advanced stages of development and adults prefer to feed on mixed diet, exhibiting zoophytophagous behavior. Nymphs of E. annulipes fed with mixed diet presented higher number of antenomers in the third, fourth and fifth instars, originating a larger number of females. Regardless of the diet consumed, fifth and sixth instars of E. annulipes were longer than the fourth instar adults.
A ordem Dermaptera é composta por espécies consideradas predadoras generalistas, muito utilizadas no controle biológico de diversos insetos-praga. A tesourinha, Euborellia annulipes (Dermaptera: Anisolabididae) é uma espécie onívora, considerada um importante agente controlador de larvas e pupas do bicudo e de outros insetos-praga de importância econômica. No entanto, alguns poucos estudos afirmam que essa tesourinha é predominantemente fitófaga, com potencial de tornar-se praga secundária em cultivos protegidos. Portanto, o objetivo desta pesquisa foi avaliar o desenvolvimento e a sobrevivência de E. annulipes com folhas de algodão e/ou larvas do bicudo. O experimento foi conduzido no laboratório de Entomologia da Embrapa Algodão, município de Campina Grande, Paraíba, Brasil. O delineamento experimental utilizado foi inteiramente ao acaso, com três tratamentos e 50 repetições. Os tratamentos consistiram de ninfas da tesourinha alimentadas com: (1) disco de folhas de algodão e água (dieta vegetal); (2) larvas de terceiro instar do bicudo e água (dieta animal) e (3) larvas do bicudo, folha de algodão e água (dieta mista). As ninfas da tesourinha foram alimentadas „ad libitum' com uma das três dietas mencionadas e mantidas em câmaras climatizadas do tipo B.O.D. a 25°C, umidade relativa de 60±10% e fotoperíodo de 12 horas até o término do bioensaio. Posteriormente, adultos da tesourinha foram sexados, agrupados em casais para cópula e, depois de acasalados individualizados em potes plásticos e alimentados com os três tipos de dieta mencionados e mantidos em câmara climatizada até a morte. Foram determinadas a sobrevivência e a duração de cada instar e fase ninfal de E. annulipes, registrando-se o intervalo, em dias, entre ecdises, assim como, a razão sexual, longevidade dos adultos e os seguintes dados morfométricos: comprimento do corpo, peso, número de antenômetros e de segmentos abdominais. Os resultados obtidos nesta pesquisa indicam que apenas o consumo de dieta vegetal por E. annulipes não é suficiente para atender as exigências nutricionais de seus estágios imaturos. Ninfas de estágios iniciais de desenvolvimento preferem se alimentar de dieta animal, enquanto os estágios mais avançados de desenvolvimento e os adultos preferem se alimentar de dieta mista, apresentan do comportamento zoofitófago. Ninfas de E. annulipes alimentadas com dieta mista apresentaram maior número de antenômeros nos terceiro, quarto e quinto instares, originando maior número de fêmeas. Independente da dieta consumida, adultos de quinto e sexto instares de E. annulipes foram mais longevos que os de quarto ínstar.

Los hábitats utilizados por las tortugas marinas durante su desarrollo varían notablemente en cuanto a características ambientales y disponibilidad de alimento. Comprender los factores que determinan la selección del hábitat y de la dieta resulta esencial para comprender la interacción que existe entre dichas especies y sus hábitats. Dicho conocimiento también proporciona datos para adoptar medidas de gestión y conservación destinadas a restaurar y mantener las poblaciones de tortugas marinas y así, su función ecológica en el ecosistema. Las zonas costeras de Brasil, Uruguay y Argentina albergan diversos hábitats de importancia para la alimentación de los juveniles de la tortuga verde, pero todavía existe un gran desconocimiento sobre la ecología trófica de esta especie durante la fase juvenil de transición desde hábitats pelágicos a bentónicos. En esta tesis se ha estudiado cómo se produce el asentamiento de las tortugas verdes en la costa de Brasil, incluyendo la selección del hábitat y la adquisición de un microbioma adecuado para la digestión de material vegetal. Los resultados demuestran que el asentamiento de las tortugas verdes a lo largo de la costa oriental de Sudamérica está fuertemente influido por la corriente del Brasil y que el cambio ontogenético es rápido en las zonas tropicales y más lento en las subtropicales, a pesar de la rápida adquisición de una microbiota capaz de degradar polisacáridos complejos en ambas zonas. Dicha microbiota resulta en una gran eficiencia en la digestión de algas, especialmente de las Rodophyta, pero no impide la digestión de presas animales. Por último, las tortugas juveniles seleccionan de forma preferente para su alimentación zonas de arrecife de baja rugosidad, someras y con poco coral vivo.
The habitats used by marine turtles during their development vary largely in environmental conditions and food availability. Understanting habitat selection is critical to the implementation of successful management and conservation actions aiming to restore and maintain sea turtle populations and, thus, their ecological function in the ecosystem. The coastal areas of Brazil, Uruguay and Argentina have a diversity of coastal habitats supporting feeding grounds for the green turtle, but there is still a lack of knowledge about the feeding ecology of this species during the juvenile transition phase from pelagic habitats to neritic habitats. This thesis has studied the settlement of green turtles in the coastal habitats of Brazil, including the ontogenetic diet shift. Results show that the settlement of green turtles along the eastern coast of South America is strongly influenced by the Brazilian current and that the ontogenetic change is fast in the tropics and slower in the subtropics, despite a fast acquisition of a microbiota capable of fermenting complex polysaccharides shortly after settlement. Such microbiome is highly efficient for the digestion of macroalgae, particularly Rodophyta, but does not impede the digestion of animal matter. Finally, preferred foraging grounds are shallow, have a low rugosity and little live coral.

Size-dependent differences between individuals in size-structured organisms have fundamental effect on population and community dynamics. Intraguild predation (IGP) is one specifically interesting constellation that often arises when two size-structured populations interact. Ontogenetic bottlenecks that determine population size-structure are affected by both population intrinsic as well as population extrinsic factors, and are therefore context-dependent. Surprisingly, size-structured IGP systems have mainly been investigated theoretically and especially long-term empirical studies are widely lacking. In this thesis I investigate empirically how habitat complexity, interaction strength, and stage-specific resource availabilities affect population processes and their effects on the dynamics of a size-structured IGP system. I conducted multi-generation experiments in a size-structured IGP system, with the Least Killifish (Heterandria formosa) as IG prey and the Common Guppy (Poecilia reticulata) as IG predator. With no alternative resource next to the shared resource, IG predator and IG prey could not coexist. Weak interactions only increased IG prey and IG predator persistence times and observed exclusion patterns depended on habitat complexity. An alternative resource for either the juvenile IG predator or the juvenile IG prey on the other hand promoted coexistence. However, this coexistence was context-dependent. Ontogenetic bottlenecks played a central role in the dynamics of the size-structured IGP system in general. In the final study I show that an ontogenetic bottleneck can, through changes in stage-specific resource availabilities, be affected in a way that leads to increased trophic transfer efficiency with potential effects on higher trophic levels. Overall, the results emphasize importance of the broader context in which size-structured communities are embedded. Especially, when managing natural communities it is important to account for the combined effects of size-structure, stage-specific resource availabilities, and habitat structure. Specifically, when managing species that connect habitats or ecosystems all life-stages’ environmental conditions must be consider in order to ensure strong predictive power of tools used for ecosystem management planning.

Lagoas costeiras, são corpos de água doce numerosos ao longo da costa brasileira, destacam-se principalmente como habitats para organismos aquáticos. São no entanto acossistemas sujeitos a grandes impactos antrópicos. No presente trabalho foram estudadas quatro lagoas costeiras da Área de Proteção Ambiental Parque das Dunas, em Salvador, Bahia, em dois períodos sazonais, chuvoso e seco, nos quais as lagoas foram comparadas. A comunidade de macroinvertebrados bentônicos foi utilizada como bioindicadora da qualidade ambiental. Dentre os organismos bentônicos, as larvas da família Chironomidae foram as mais frequentes e abundantes, sendo também estudada a dieta das mesmas com o objetivo de conhecer o papel desses organismos na estrutura e dinâmica trófica destas comunidades, através da observação de itens alimentares presentes no conteúdo de seus tubos digestivos. Os resultados da obtidos evidenciaram que as lagoas Vitória, Junco e Camarão tiveram águas com pH ácido, relativamente bem oxigenadas e de condutividade elétrica moderada em ambos os períodos amostrados. A riqueza de táxons foi moderada nas lagoas Vitória e Junco, variando de 13 a 21 táxons, e baixa nas lagoas do Camarão e Negra variando entre 8 e 14 táxons. Em relação à similaridade na composição das comunidades, as lagoas Vitória e do Camarão foram as mais semelhantes (50%), e a lagoa Negra a mais dissimilar (20%). Os indicadores utilizados evidenciaram que todas as lagoas estão perturbadas e necessitando ações de manejo, porém a Lagoa Negra deve ser priorizada quanto a ações de restauração. Em relação à ecologia trófica das larvas da família Chironomidae, os resultados evidenciaram o consumo de diversos itens alimentares como: algas, pequenos invertebrados, matéria orgânica amorfa e detrito particulado inorgânico. De acordo com o modo de alimentação e os itens consumidos, os diferentes táxons foram classificados em quatro grupos tróficos funcionais distintos: os Coletores - catadores detritívoros, o qual abrangeu a maioria dos gêneros de quironomídeos registrados nas lagoas; os Coletores- catadores herbívoros e os Predadores-onívoros, o qual abrangeu todos os gêneros de Tanypodinae e os Fragmentadores. Pode-se concluir que a onivoria é a provável estratégia que permite a coexistência de organismos de diferentes táxons aumentando assim a riqueza das larvas de Chironomidae nas lagoas costeiras avaliadas.
Coastal lakes are numerous freshwater bodies along Brazilian coast, being principally as habitats for the aquatic biota. They are nevertheless subject to great anthropogenic impacts. In the present work four coastal lakes located in the Protection Area of Parque das Dunas, in Salvador, Bahia, in two contrasting seasonal periods, the dry and the rainy periods, in which the lakes were compared. The benthic macro-invertebrates community was used as bio-indicator of environmental quality. Among the benthic organisms the dipteran larvae of the Chironomidae family were the most frequent and abundant. Their diet was also studied aiming to know the role of these organisms in the structure and trophic-dynamics of theses community by the analysis of the food items in their digestive tube. The results obtained have shown that lakes Vitória, Junco and Camarão had acidic, relatively well oxygenated and of moderate electrical conductivity waters in both periods sampled. The richness of taxa was moderate in lakes Vitória and Junco, varying from13 to 21 taxa, and low in lakes Camarão and Negra, varying between 8 and 14 taxa. Regarding the similarity among communities composition, lakes Vitória and Camarão were the most similar (50%), and Lake Negra the most different (20%). The indicators used evidenced that all lakes are under disturbances and require management actions, however, Lake Negra should be the priority for restauration actions. In relation to the trophic ecology of the Chironomidae larvae, the results evidenced the consumption of many food items as: algae, small invertebrates, decomposing organic matter, and particulate inorganic detritus. According to their feeding modes and consumed items the different taxa were classified in four distinct functional trophic groups: Collector-gatherer-detritivores, that comprised most chironomid taxa recorded in the coastal lakes; the Collector-gatherer-herbivores, the Predator-omnivores comprising all genera of the sub-family Tanypodinae and the Shredders. We concluded that probably omnivory is the strategy allowing the co-existence of organisms from many different taxa, being responsible for the richness of Chironomidae in the benthic communities of the studied coastal lakes.

Made available in DSpace on 2014-12-17T14:33:04Z (GMT). No. of bitstreams: 1 FranciscoRV_DISSERT.pdf: 943640 bytes, checksum: d6134d4d93c5e755e9cda7290579f131 (MD5) Previous issue date: 2010-07-02
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The omnivorous filter-feeding fish, Nile tilapia (Oreochromis niloticus), can have negative effects on water quality enhancing the eutrophication process. These effects depend on the nutrient enrichment level in the water. We carried out a mesocosm experiment for five weeks in a tropical man-made lake in Brazil to test ifthe effects of tilapias depend on of the level of nutrient enrichment. The experiment lasted for 5 weeks and a factorial 2x5 experimental design was used where the presence and absence of tilapias were manipulated in combination to 5 different levels of nutrient load in a total of 10 treatments. A two way repeated measure ANOVA was performed to evaluate the effects of time (t), tilapia (F), nutrients (NP) and the interactions among these factors on: chlorophyll a, water transparency, total phosphorous, total nitrogen, N:P ratio, zooplankton biomass and phytoplankton biovolume. The tilapia effect was evident, but nutrient enrichment didn t have any effect on the variables analyzed. Tilapia decreased the water transparency, total zooplankton biomass, calanoid copepod biomass, nauplii copepod biomass and cladocerans biomass. On the other hand, tilapia had no effect on phytoplankton biovolume. This lack of effect on phytoplankton is probably due to tilapia grazing that may counteract the positive effect of tilapia on phytoplankton via trophic cascades and nutrient recycling. Hence, a reduction in tilapia stock would not be an effective way to reduce phytoplankton biomass and improve water quality
A til?pia do Nilo (Oreochromis niloticus) ? um peixe on?voro filtrador que pode ter efeitos negativos sobre a qualidade da ?gua favorecendo o processo de eutrofiz??o. Esses efeitos negativos dos peixes on?voros filtradores devem ser dependentes do n?vel de enriquecimento da ?gua por nutrientes. N?s realizamos um experimento em mesocosmos por cinco semanas em um lago artificial tropical para testar se os efeitos das til?pias s?o dependentes do n?vel de enriquecimento por nutrientes. O experimento teve dura??o de 5 semanas e consistiu num delineamento fatorial 2x5 onde 2 n?veis de til?pia (presen?a e aus?ncia) foram manipulados em combina??o com 5 diferentes niveis (aportes) de nutrientes num total de 10 tratamentos.. Uma ANOVA bifatorial com medidas repetidas no tempo foi realizada para testar os efeitos do tempo (t), da til?pia (F) e do nutriente (NP) e os efeitos de suas intera??es sobre a clorofila a, transpar?ncia do disco de Secchi, concentra??o de f?sforo e nitrog?nio total e a raz?o entre eles (N:P), al?m do efeito sobre a biomassa da comunidade zooplanct?nica e o biovolume de fitopl?ncton. O efeito da til?pia foi evidente, enquanto o enriquecimento por nutrientes n?o mostrou efeito algum. Quando presente, a til?pia diminuiu a transpar?ncia do disco de Secchi e a biomassa total do zoopl?ncton, de cop?podos calan?ides, na?plios de cop?podos e de clad?ceros. Por?m, nenhum efeito foi detectado da til?pia sobre o biovolume do fitopl?ncton. Essa aus?ncia de efeito pode ser devido a herbivoria da til?pia que contrabalan?a os seus efeitos positivos via cascata tr?fica e ciclagem de nutrientes. Desta forma, uma redu??o do estoque pesqueiro de til?pias para promover uma melhoria na qualidade da ?gua n?o afetaria a biomassa fitoplanct?nica e consequentemente n?o atingiria o seu objetivo

The feeding ecology of a common saltmarsh crab, Armases cinereum (Armases), was investigated to determine how habitat (mangrove vs. ecotone, natural mangrove vs. modified mangrove fringe) influenced this species’ feeding behavior and trophic ecology in its southwestern Florida, USA, distribution. In the laboratory, Armases’ preference for mangrove material was examined using leaves of three mangrove species (Avicennia germinans, Laguncularia racemosa, and Rhizophora mangle) and leaves of different degradation levels (fresh, senescent, and partially-decomposed). Leaf material from A. germinans was preferentially consumed over the other taxa at fresh and partially-decomposed levels of leaf decay. When Armases were offered a choice between four common upland vegetation types (Iva frutescens, Borrichia frutescens, Nephrolepis biserrata, and Stenotaphrum secundatum), the preferred mangrove from the previous experiment (A. germinans, partially-decomposed), and an animal prey item (Gryllodes sigillatus, cricket), Armases displayed greatest selectivity for the animal prey item and high selectivity for both I. frutescens and A. germinans plant taxa (Manly-Chesson α selectivity and Chesson ϵ electivity). Field-based stable isotope analysis was used to determine trophic position and reconstruct dietary proportions of Armases across three pairs of natural and heavily-modified sites within Tampa Bay to determine whether Armases feeding behavior is impacted by the presence of upland forest adjacent to mangrove forest habitat. Analysis of trophic position based on δ15N signatures of Armases from each of the six populations revealed that Armases in habitats with modified connectivity had lower trophic variability and significantly higher average trophic position compared to Armases sampled from the three sites with natural connectivity. Stable isotope diet reconstruction using the Bayesian mixing model SIMMR further established Armases preference for animal-derived food material in habitats with natural and modified connectivity. This preference is likely driven by high selectivity for sources rich in Nitrogen (i.e., animal tissue, partially-decomposed A. germinans material, and I. frutescens). I determined that the use of laboratory experiments in conjunction with stable isotope mixing models is important in accurately investigating feeding preferences of Armases in mangrove intertidal regions. Together, my results show that the diet of Armases is broadly omnivorous and populations can be influenced by the heterogeneity of their habitat. Further feeding experiments, dietary analyses and a longer sampling period are needed to more definitively identify the patterns of Armases detritivory in mangrove and ecotonal upland habitats.

Blue Catfish Ictalurus furcatus are native to tributaries of the Mississippi River but are now invasive in several Atlantic slope drainages. This includes subestuaries of the Chesapeake Bay, where their feeding ecology and potential impact on native species was largely unknown. We collected stomach contents from 16,110 Blue Catfish at 698 sites in three large subestuaries of the Chesapeake Bay (James, York, Rappahannock rivers). Cumulative prey curves revealed that sample size was sufficient for diet description, though 1,000 – 1500 stomachs were needed per river. Blue Catfish are opportunistic generalists that feed on a broad array of plant and animal material. Logistic regression models reveal that Blue Catfish undergo significant ontogenetic diet shifts to piscivory at larger sizes (P<0.01) though the lengths at which these shifts occur varies by river system (500 – 900 mm total length; TL). Over 60% of Blue Catfish stomachs contained other invasive species, primarily Hydrilla verticillata and Asian clams Corbicula fluminea. Canonical Correspondence Analysis (CCA) revealed that salinity and season explained the most variation in Blue Catfish diet, while Generalized Additive Models (GAMs) demonstrated that there is considerable spatiotemporal and length-based variation in predation of species of concern. Species of concern include American Shad, American Eel, and river herring, which are imperiled, and blue crab, which support valuable fisheries in Chesapeake Bay. Predation of American Shad, American Eel, and river herring was rare (max predicted occurrence in Blue Catfish diets = 8%), while blue crab was much more common in the diet (max predicted occurrence =28%). Predation of American Shad and river herring peaks in freshwater areas in April, while predation of blue crab peaks in brackish areas in October. Predation of all species of concern is highest for large catfish (500 – 1000 mm TL). Field and laboratory-based estimates of consumption rate revealed that Blue Catfish feed at similar rates as Channel Catfish Ictalurus punctatus, and daily ration is estimated to be 2-5% bodyweight per day during warm temperatures, while peak feeding (maximum daily ration) can approach 10% bodyweight per day. While consumption of imperiled species is rare, Blue Catfish could still have negative impacts on these species due to dense catfish populations.
Ph. D.

Made available in DSpace on 2014-12-17T14:01:57Z (GMT). No. of bitstreams: 1 RosembergFM.pdf: 688143 bytes, checksum: b1661c0d65a3b582ed47216926346188 (MD5) Previous issue date: 2008-06-02
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
?The major aim of this study was to test the hypothesis that the introduction of the Nile tilapia (Oreochromis niloticus) and the enrichment with nutrients (N and P) interact synergistically to change the structure of plankton communities, increase phytoplankton biomass and decrease water transparency of a semi-arid tropical reservoir. One field experiment was performed during five weeks in twenty enclosures (8m3) to where four treatments were randomly allocated: with tilapia addition (T), with nutrients addition (NP), with tilapia and nutrients addition (T+NP) and a control treatment with no tilapia or nutrients addition (C). A two-way repeated measures ANOVA was done to test for time (t), tilapia (T) and nutrient (NP) effects and their interaction on water transparency, total phosphorus, total nitrogen, phytoplankton and zooplankton. The results show that there was no effect of nutrient addition on these variables but significant fish effects on the biomass of total zooplankton, nauplii, rotifers, cladocerans and calanoid copepods, on the biovolume of Bacillariophyta, Zygnemaphyceae and large algae (GALD ? 50 ?m) and on Secchi depth. In addition, we found significant interaction effects between tilapia and nutrients on Secchi depth and rotifers. Overall, tilapia decreased the biomass of most zooplankton taxa and large algae (diatoms) and decreased the water transparency while nutrient enrichment increased the biomass of zooplankton (rotifers) but only in the absence of tilapia. In conclusion, the influence of fish on the reservoir plankton community and water transparency was greater than that of nutrient loading. This finding suggests that biomanipulation should be a greater priority in the restoration of eutrophic reservoirs in tropical semi-arid regions
?O principal objetivo deste estudo foi testar a hip?tese de que a introdu??o da til?pia do Nilo (Oreochromis niloticus) e o enriquecimento por nutrientes (N e P) interagem sinergicamente ocasionando mudan?as na estrutura da comunidade planct?nica atrav?s do aumento da biomassa fitoplanct?nica e diminui??o da transpar?ncia da ?gua em um reservat?rio tropical do semi-?rido. Um experimento de campo foi realizado durante cinco semanas em vinte mesocosmos (8m3) nos quais quatro tratamentos foram alocados aleatoriamente: com adi??o de til?pia (T), com adi??o de nutrientes (NP), com adi??o de til?pia e nutrientes (T+NP) e um tratamento controle sem adi??o de til?pia ou nutrientes (C). Uma ANOVA bifatorial com medidas repetidas foi realizada para testar os efeitos do tempo, da til?pia (T) e dos nutrientes (NP) e seus efeitos de intera??o sobre a transpar?ncia da ?gua, f?sforo total, fitopl?ncton e zoopl?ncton. Os resultados mostraram que n?o houve efeito da adi??o de nutrientes sobre essas vari?veis mas houve um efeito significativo dos peixes sobre a biomassa do zoopl?ncton total, n?uplios, rot?feros, clad?ceros e cop?podos calan?ides, sobre o biovolume de Bacillariophyta, Zygnemaphyceae e algas de grande porte (GALD ? 50?m) e sobre a profundidade do disco de Secchi. Al?m disso, foi encontrado um efeito significativo da intera??o entre as til?pias e nutrientes sobre a profundidade do disco de Secchi e tamb?m sobre a biomassa de rot?feros. As til?pias diminu?ram a biomassa da maioria dos taxa zooplanct?nicos, das algas de grande porte e diminu?ram a transpar?ncia da ?gua, enquanto que o enriquecimento por nutrientes aumentou a biomassa do zoopl?ncton (rotiferos) mas somente na aus?ncia das til?pias. Portanto podemos concluir que a influ?ncia dos peixes sobre a comunidade planct?nica do reservat?rio e a transpar?ncia da ?gua foi maior do que o aporte por nutrientes, sugerindo assim que a biomanipula??o deve ter maior prioridade na restaura??o de reservat?rios eutrofizados em regi?es semi-?ridas tropicais

Made available in DSpace on 2014-12-17T14:33:02Z (GMT). No. of bitstreams: 1 MariaMLC.pdf: 1068178 bytes, checksum: 2211aebe12426e9f45d52a507df28c0f (MD5) Previous issue date: 2009-05-29
Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The food chain theory predict that presence of omnivory prevent the trophic cascade and could be a strong stabilizing factor over resource and consumer community dynamics, and that the nutrient enrichment destabilize populations dynamics. Most of the freshwater tropical reservoirs are eutrophic, and strategies that seek improve the water quality through the control of phytoplankton biomass and nutrient input, become essential for the improvement and preservation of water quality. The aim of this study was test the zooplanktivory (when larvae) and omnivory (when young and adult) effects of Nile Tilapia over the structure and dynamics of plankton communities, in addition or absence of nutrients enrichment. For this, one field experiment was performed with a factorial design 2x3 resulting in six treatments: control, without fish and nutrient (C); with omnivorous fish (O); with zooplanktivorous fish (Z); without fish and with enrichment of nutrients (NP); with omnivorous fish and nutrients (ONP); and, with zooplanktivorous fish and nutrients (ZNP). The two planktivory types reduced the zooplankton biomass and increased the phytoplankton biomass, but the omnivory of filter-feeding fish attenuated the trophic cascade magnitude. The fertilization by nutrients increases the nutrient concentrations in water and the phytoplankton biomass, but the effect on zooplankton is dependent of the trophic structure. In a general way, the effects of the fish and nutrient addition were addictive, but significant interactions among those factors were observed in the answer of some zooplankton groups. The effects of omnivorous fish over the temporal variability of phytoplankton and zooplankton biomass were very variable, the increase or reduce in variability of the plankton depending of the level of nutrients and of the analyzed variable. With base in this study, we conclude that the planktivory type exercised by the fish and the concentrations of nutrients in the water affects the force of pelagic trophic cascades and probably the success of biomanipulation programs for the handling of water quality in lakes and tropical reservoirs
A teoria de cadeias alimentares prev? que a presen?a de onivoria pode atenuar os efeitos de cascata tr?fica e estabilizar as popula??es de aut?trofos e herb?voros, as quais s?o desestabilizadas pela fertiliza??o por nutrientes. Tendo em vista que muitos lagos e reservat?rios tropicais encontram-se eutrofizados, estrat?gias que visem o controle do aporte de nutrientes e a redu??o da biomassa fitoplanct?nica s?o essenciais para a melhoria da qualidade da ?gua desses ambientes. O presente estudo teve como objetivo avaliar o efeito da zooplanctivoria e onivoria por uma mesma esp?cie de peixe (Til?pia do Nilo), que quando larva ? zooplanct?vora e quando jovem e adulta torna-se filtradora on?vora, sobre a estrutura e din?mica das comunidades planct?nicas, na presen?a e aus?ncia de enriquecimento por nutrientes. Para tanto, foi realizado um experimento com desenho fatorial 2 x 3, resultando em 6 tratamentos: sem adi??o de peixes ou nutrientes (C); com adi??o de peixes zooplanct?voros (Z); com adi??o de peixes on?voros (O); com adi??o de nutrientes (NP); com adi??o de peixes zooplanct?voros e nutrientes (ZNP); e com adi??o de peixes on?voros e nutrientes (ONP). Os resultados mostram que os dois tipos de planct?voros reduziram a biomassa zooplanct?nica e aumentaram a biomassa fitoplanct?nica, mas que a onivoria dos peixes filtradores atenuou a magnitude das cascatas tr?ficas. Os resultados tamb?m mostram que a fertiliza??o por nutrientes aumenta as concentra??es de nutrientes na ?gua e a biomassa fitoplanct?nica, mas que o efeito sobre o zoopl?ncton depende da estrutura tr?fica. De um modo geral, os efeitos da adi??o de peixes e nutrientes foram aditivos, mas intera??es significativas entre esses fatores foram observadas na resposta de alguns grupos zooplanct?nicos. Os efeitos dos peixes on?voros sobre a variabilidade temporal da biomassa do fitopl?ncton e do zoopl?ncton foram muito vari?veis, aumentando ou reduzindo a variabilidade do pl?ncton dependendo do n?vel de nutrientes e da vari?vel analisada. ? poss?vel concluir, com base neste estudo, que o tipo de planctivoria exercido pelos peixes e as concentra??es de nutrientes na ?gua afetam a for?a das cascatas tr?ficas pel?gicas e provavelmente o sucesso dos programas de biomanipula??o para o manejo da qualidade da ?gua de lagos e reservat?rios tropicais

In the middle of the 1990s many adolescents became vegetarians. There was concern among adults about whether these new young vegetarians got enough energy and nutrients from their dietary intake. The aim of this thesis was to investigate the prevalence of young vegetarians, the food and lifestyle habits, dietary intake and nutritional status of vegetarian and omnivorous adolescents. The prevalence of adolescents eating a vegetarian school lunch in 124 Swedish secondary schools was investigated by interviewing matrons. Information about prevalence of vegetarians, food and lifestyle habits, of 2041 15-year old students from Umeå, Stockholm and Bergen, was obtained by a questionnaire. The dietary intake and nutritional status of thirty 16-20 year-old vegans were compared with thirty age, sex and height matched omnivores. Five percent of the adolescents (16-20 years) in Sweden were found to eat vegetarian food at school lunch. In Umeå there was a significantly higher prevalence (15.6%) of 15-year-old vegetarians compared with Stockholm (4.8%) and Bergen (3.8%). It was also found that more females than males (15 years old) chose a vegetarian dietary regime. Even though the female vegetarians consumed vegetables significantly more often than the omnivores, the intake (32 times/month) was not as often as might be expected of a vegetarian population. The male vegetarians reported eating vegetables not even once a day (25 times/month). No difference in the consumption frequency of fruits/berries, alcoholic beverages, sweets/chocolates and fast foods was seen between vegetarians and omnivores. However, female vegetarians more often than female omnivores consumed dietary supplements. Furthermore, lifestyle characteristics of vegetarians were similar those of omnivores regarding exercise, use of alcohol and smoking habits. No significant difference in validity of reported energy expenditure or energy and protein intakes was found between vegans and omnivores. Young vegans (16-20 year-olds) were seen to have a higher calculated intake of vegetables, legumes, and dietary supplements and a lower intake of ice creams, cakes/cookies, and candies/chocolate than omnivores. The dietary intake was below the average requirements of riboflavin for 73% of the vegans, vitamin B12 for all vegans, vitamin D for 43% of the vegans, calcium for 77% of the vegans and selenium for all vegans and 43% of the omnivores. If intake of supplements was included the intake of e.g. calcium and selenium was still lower than the average requirements for 67% and 73% of the vegans respectively. Low iron stores were as prevalent among vegans as among omnivores (20% and 23% with low stores) and three vegans had low vitamin B12 concentrations in blood. The findings imply that food and lifestyle habits of young vegetarians are different than what previous studies of vegetarians have shown. There is a need for future research of the long-term health effects of being vegetarian.

Sandy beach ecosystems have been studied worldwide; however, ecological data are sparse for the extensive barrier islands of Florida. Accordingly, I investigated the feeding patterns of the ghost crab (Ocypode quadrata), a dominant omnivore inhabiting beaches along the Floridian coast. Density data was collected for ghost crabs and swash macroinfaunal prey. In addition, I utilized stable isotopes in conjunction with the mixing models IsoSource and SIAR to characterize diets of ghost crabs across three barrier islands in spring and summer 2011. Results showed that ghost crabs at Cayo Costa feed primarily on swash macroinfauna, while those from Anclote Key shifted their diet to one comprised primarily of semi-terrestrial amphipods. However, at Honeymoon Island, ghost crab isotopic signatures were best explained by a mixed diet of both macroinfauna and wrack-associated prey. The unique consumption of wrack fauna at Anclote Key co-occurs with comparatively low infaunal densities and biomass, and modified ghost crab behavior due to trait-mediated effects. My results are novel because they suggest that wrack-associated fauna may be an important food source for ghost crabs in certain beach regimes.

Osämja mellan människan och rovdjuren har funnits sedan vi slutade jaga och började bruka jorden och bedriva lantbruk. En av de absolut viktigaste faktorerna som bestämmer vart en art förekommer, hur stark en stam är och hur den förändras över tiden, är predation. I svensk historia har både rådjurs (Capreolus capreolus) och rödräven (Vulpes vulpes) båda populationer varit nära nationell utrotning. Syftet med uppsatsen är att ta reda på om räven har någon påverkan på rådjurspopulationen. Detta görs genom att analysera avskjutningsstatistik från viltdata.nu i tre olika län med liknande klimat och innehåller samma arter av predatorer. Analysen gjordes med korrelationsanalys. Dock var det inget utav resultaten som visade någon signifikans. Dessa olika resultat i de olika län tyder på att det finns andra faktorer än räven som påverkar rådjurspopulationen.
A conflict between humans and predators has existed since man stopped hunting and started with agriculture instead. We know today that one of the most important factors influencing the distribution and abundance of a species is predation. Over the last two? centuries, both the roe deer (Capreolus capreolus) population and the red fox (Vulpes vulpes) population have been very close to extinction in Sweden. The purpose of this study was to determine if the red fox population affects the roe deer population. This was done by analyzing hunting statistics from viltdata.nu in three different regions with similar climate and with the same type of carnivores. The analysis was performed using correlation analysis. None of the relationships between roe deer and the fox in the three different areas was significant. This indicates that there are factors other than predation by fox that influence the deer population.

Using data from the 1982, 1985, 1992, and 1997 Survey of Public Participation in the Arts (SPPA), this thesis tests the effects of class, age, gender and race on the breadth of musical preferences that respondents report to liking. Specifically, the omnivore/univore framework developed by Peterson (1992) is examined.

It is hypothesized that age and social class are positively related to musical omnivorousness (liking a wide variety of music). That is, older people and people higher in social economic standing will be more omnivorousness in musical preferences. The underlying theory here is that in today's society, being omnivorous is a form of cultural capital. Cultural exclusivity is no longer valued as it may have been in the past and is more often a sign of ignorance rather than status. Hence, the hypothesis is that people today will use a wide knowledge of musical forms to help them network and "get ahead." This should be more important for people as they age because the need to network as a way of moving higher in the social economic hierarchy should be more important.

Additionally, it is hypothesized that women and whites will be more omnivorousness because they may feel less alienated in general from mainstream society, especially at younger ages. Hence, blacks and men will gravitate towards fewer genres of musical as a symbolic rejection of the values of mainstream society. This should also be more salient when people are younger.

Overall, the findings presented support the contention the omnivorousness is replacing exclusiveness as a sign of status. Indeed, the findings show that class is positively related to omnivorousness, age is positively related to omnivorousness, being female is positively related to omnivorousness, and that whites are more omnivorous than blacks.

Perhaps most interesting, however, is that the relationship between age and omnivorousness was determined to be a curvilinear relationship. No other analysts have reported this. Moreover, the findings present evidence that age may indeed be a more important determinant of musical omnivorousness than social class. Hence, it is concluded that no longer should musical preferences be examined simply as varying by social class but also as changing across the life cycle.

Master of Science

From different traditions, research in the field of sociology of cultural taste and consumption has argued that contemporary societies are symbolically stratified through cultural engagement. These theoretical frameworks differ mainly in their explanations of the mechanisms that shape the relationship between culture and social stratification. Motivated by concepts from Pierre Bourdieu, Richard A. Peterson, and other key scholars, this thesis is focused on addressing the relationship between music consumption and social stratification. Due to its peculiar characteristics, music provides a good illustration of how people, through cultural engagement, draw boundaries that symbolically differentiate social groups. Although literature in the area has made great progress, there are still theoretical and empirical gaps. It is possible to find some passionate views which deny the relevance of some operationalisations and methods over others (Wuggenig, 2007; Chan, 2010a). From a comparative point of view it is questioned whether different dimensions of cultural practices can deliver consistent results (Peterson, 2005; Purhonen, Gronow and Rahkonen, 2011; Yaish and Katz-Gerro, 2012). Research which focuses on comparisons between societies frequently lacks detailed theoretical conceptualisations regarding how cultural items are distributed in different social settings (Katz-Gerro, 2011; Purhonen and Wright, 2013). Other important gap in the literature is the lack of understanding about how technologies act as an element of social distinction (López-Sintas, Cebollada, Filimon and Gharhaman, 2014). The main objective of this research is therefore to review how research has defined and studied the relationship between culture and society across several perspectives and to offer new insights which significantly contribute to the advancement of knowledge of the sociology of cultural taste and consumption. This is motivation for the development of four research articles which use several quantitative methods to analyse survey data from Austria, England, Chile, Finland, Israel and Serbia. This thesis shows that musical engagement, regardless of how and where it is measured, remains socially stratified. Age is the primary stratifying factor for musical engagement, highlighting the distinction between popular music preferred by the younger age cohorts, and the classical or traditional music of the older. Both are reinforced by educational level and social class. Individuals displaying broader musical preferences are more likely to be in advantageous positions. This concurs with arguments about omnivorism as a manifestation of cultural homology in the classic Bourdieusian sense (Lizardo and Skiles, 2012). Thanks to the innovative analysis of available data and the use of more specific cultural indicators it is possible to elaborate research questions to address the study of musical engagement and its place in society, integrating research methods, theory of practices, local and global contexts, and technologies as salient analytical dimensions.

Background Meat is one of the most nourishing and highly consumed foods, but the controversy around theconsumption of meat products, and the negative effects around the consumption of meatproducts led to increased scholarly attention on the user willingness to alter their meatconsumption. In Sweden, a guideline by the Livsmedelsverket (The Swedish National Food Agency) in 2015 encouraged people to consume less red and processed meat. This was because 72 per cent of men and 42 per cent of women in Sweden have individual consumption levels that exceed the 500 grams per week of red and processed meats as recommended by the World Cancer Research Fund. Objective This planned mixed-methods study inquires about the attitudes of young adult omnivorestowards the reduction of meat intake, their expected liking of changing dietary habits, andmotivation towards the reduction of meat consumption in Sweden. Changing dietary habits inthe current context refers to the participant’s willingness to favour meat alternatives. Methods The current study is a convergent mixed method design using both a quantitative survey andqualitative interviews to collect primary data. Results and conclusion The participants from both the qualitative and quantitative study are broadly worried about thehealth problems associated with high meat consumption and motivation for reducing meatconsumption was based on health as well as ethical issues. Being opposed to reducing meatconsumption is a common position for young adult omnivores.
Bakgrund Kött är ett av de mest näringsrika och mest konsumerade livsmedlena. Med anledning av attman funnit negativa effekter av en hög konsumtion av kött har man vetenskapligt alltmer börjatintressera sig för konsumentens vilja att ändra sin köttkonsumtion.I Sverige uppmanade Livsmedelsverket Sveriges befolkning att konsumera mindre rött kött ochbearbetade köttprodukter. Bakgrunden till detta var att 72 % av männen och 42 % av kvinnornai Sverige har individuella konsumtionsnivåer som överstiger 500 gram av rött kött ochbearbetade köttprodukter per vecka, vilket är en maxrekommendation från Världscancerforskningsfonden. Mål Denna bland metodstudie undersöker attityden för att minska köttkonsumtionen hos unga vuxna allätare i Sverige, deras förväntade åsikter kring förändrade kostvanor samt deras motivation att minska sin köttkonsumtion Metoder I den aktuella studien ingår en metoddesign som innefattar både en kvantitativ undersökning och kvalitativa intervjuer för att samla in primära data. Resultat och slutsats Deltagarna från både den kvalitativa och den kvantitativa undersökningen är i stort sett överensstämmande och visar att försökspersonerna är oroliga för de hälsoproblem som är förknippade med hög köttkonsumtion och deras motivation för att minska köttkonsumtionen baserades på frågor kring hälsa och etik. Det var vanligt förekommande bland försökspersonerna att vara bunden till köttkonsumtion.

Over the last three decades there has been a significant increase in aquaculture production and the demand for farmed fish is predicted to rise further. More fish are being caught to become fishmeal in aquaculture, than for direct human consumption use, while a large number of fish stocks are being depleted. Many popular farmed species are carnivores and thus brought up on a diet consisting of fishmeal and fish oil. However, several studies have shown that several fish species can be brought up on a diet consisting of mussel meal instead of fishmeal. If so, this finding can possibly lead to a more sustainable fishing in the future by reducing the number of wild-caught fish. The purpose of this study has been to examine if mussel meal extract can induce foraging in the omnivorous species crucian carp (Carassius carassius), a commercial fish that is mainly farmed in China. Induced foraging can indicate that crucian carp could become accustomed to mussels, even though mussels are not part of its natural food source. The results revealed that foraging was induced in the crucian carp by conventional feed for carp, the control diet, but not by extract of mussels.
Vattenbruket har ökat markant under de senaste tre decennierna och idag går mer fisk till foderproduktion för fiskodlingar än vad som konsumeras direkt av människan. Detta är problematiskt då många fiskbestånd är utarmade, samtidigt ökar efterfrågan på fisk. Många populära matfiskar är rovfiskar som huvudsakligen matas med fiskbaserat foder. Ett flertal studier har emellertid visat att flera fiskarter potentiellt kan födas upp på blåmusslor (Mytilus edulis) istället för fiskbaserat foder. Foder som huvudsakligen baseras på musslor kan därför i framtiden möjligen bidra till att minska överexploatering av fisk. Denna studie undersökte om musselextrakt kan inducera ett födosök hos omnivoren ruda (Carassius carassius), som idag odlas och används som matfisk framförallt i Kina. I så fall kan det indikera att ruda möjligen kan vänjas vid musslor, trots att det inte ingår i fiskens naturliga föda. Resultaten i studien visade att ett födosök inducerades hos ruda gentemot extrakt av vanligt karpfoder, kontrollsubstansen, men inte gentemot musselextrakt.

Since its inception, consumption behaviour theory has developed to account for the important social aspect that underpins or at least to some extent can be used to explain consumption behaviour. Modern consumption behaviour theory is anthropocentric in nature, with people and societal influence at the forefront of the theory. To date, empirical studies on consumption behaviour of cultural activities (for example, music and arts), entertainment and sport have used Bourdieu’s (1984) omnivore/univore theory to suggest that consumption of leisure activities is bound up in social ties. To date, no such investigation has been conducted in the context of sport in South Africa. The aim of the study therefore is to investigate whether South African cricket spectators are sporting omnivores or univores, thus, essentially investigating whether sports consumption behaviour in South Africa is bound up in social ties. A number of positive economic and social ramifications could result from gaining a holistic understanding of sports consumption behaviour in South Africa. Given these ramifications, the secondary goal of the research is to identify motives for consumers making specific sport consumption decisions, and determining whether certain characteristics can be attributed to these consumption decisions. Recommendations based on the findings of the research could help various stakeholders understand sports consumption patterns in South Africa, which could in turn lead to the realization of positive economic and social benefits. The study made use of a questionnaire, administered at four different limited overs cricket matches in the 2012/13 cricket season, to obtain a range of responses reflecting specific types of consumption behaviour as well as motives for consumption decisions of cricket spectators in the Eastern Cape. Using individual binary probit models and post estimation F-tests, the results indicate that consumption behaviour of sport within South Africa predominantly differs on the grounds of education and race. This suggests that there are aspects of social connotations underpinning sports consumption behaviour within South Africa

Arthropod species that have the potential to damage crops are food resources for communities of predators and parasitoids. From an agronomic perspective these species are pests and biocontrol agents respectively, and the relationships between them can be important determinants of crop yield and quality. The impact of biocontrol agents on pest populations may depend on the availability of other food resources in the agroecosystem. A scarcity of such resources may limit biological control and altering agroecosystem management to alleviate this limitation could contribute to pest management. This is a tactic of ‘conservation biological control’ and includes the provision of flowers for species that consume prey as larvae but require floral resources in their adult stage. The use of flowers for pest management requires an understanding of the interactions between the flowers, pests, biocontrol agents and non-target species. Without this, attempts to enhance biological control might be ineffective or detrimental. This thesis develops our understanding in two areas which have received relatively little attention: the role of flowers in biological control by true omnivores, and the implications of flower use by fourth-trophic-level life-history omnivores. The species studied were the lacewing Micromus tasmaniae and its parasitoid Anacharis zealandica. Buckwheat flowers Fagopyrum esculentum provided floral resources and aphids Acyrthosiphon pisum served as prey. Laboratory experiments with M. tasmaniae demonstrated that although prey were required for reproduction, providing flowers increased survival and oviposition when prey abundance was low. Flowers also decreased prey consumption by the adult lacewings. These experiments therefore revealed the potential for flowers to either enhance or disrupt biological control by M. tasmaniae. Adult M. tasmaniae were collected from a crop containing a strip of flowers. Analyses to determine the presence of prey and pollen in their digestive tracts suggested that predation was more frequent than foraging in flowers. It was concluded that the flower strip probably did not affect biological control by lacewings in that field, but flowers could be significant in other situations. The lifetime fecundity of A. zealandica was greatly increased by the presence of flowers in the laboratory. Providing flowers therefore has the potential to increase parasitism of M. tasmaniae and so disrupt biological control. A. zealandica was also studied in a crop containing a flower strip. Rubidium-marking was used to investigate nectar-feeding and dispersal from the flowers. In addition, the parasitoids’ sugar compositions were determined by HPLC and used to infer feeding histories. Although further work is required to develop the use of these techniques in this system, the results suggested that A. zealandica did not exploit the flower strip. The sugar profiles suggested that honeydew had been consumed by many of the parasitoids. A simulation model was developed to explore the dynamics of aphid, lacewing and parasitoid populations with and without flowers. This suggested that if M. tasmaniae and A. zealandica responded to flowers as in the laboratory, flowers would only have a small effect on biological control within a single period of a lucerne cutting cycle. When parasitoids were present, the direct beneficial effect of flowers on the lacewing population was outweighed by increased parasitism, reducing the potential for biological control in future crops. The results presented in this thesis exemplify the complex interactions that may occur as a consequence of providing floral resources in agroecosystems and re-affirm the need for agroecology to inform the development of sustainable pest management techniques.

During a one year longitudinal study, the dietary intake and growth of 50 vegetarian children aged 7-11 years was compared with that of 50 age-, sex- and race-matched omnivores. Diet was assessed at 6 month intervals using three, 3-day diet diaries and follow-up interviews. Anthropometric measurements (height, weight, mid-arm circumference, biceps and triceps skinfolds) were similarly taken 3 times. Multiple stepwise regression was used to control for non nutritional factors that affect growth. A questionnaire was administered at baseline to all children and their parents, to determine socio-economic status, health related behaviour and parents, ' height. Finger-prick blood samples were obtained from a sub-sample to measure haemoglobin (n=35 pairs) and cholesterol (n=32 pairs). Activity profiles were obtained using 12 hour heart-rate telemetry (n=20 pairs). Vegetarian and omnivorous groups were similar for socioeconomic group and health related behaviour. The predicted growth increment (0.47cm) of the vegetarians was significantly greater (p=0.05)' than that of the omnivores. Energy and sugars intakes of the vegetarians were significantly lower than those of the omnivores, fat and iron intakes were similar, whilst P: S ratio, NSP and calcium intakes were higher. The mean (SD) haemoglobin level of the vegetarians (11.8 (0.2g/dl)) was significantly below (p=0.04) that of the omnivores (12.4 (0.2)g/dl) but cholesterol levels were similar. Heart-rates were slightly higher for the vegetarians than the omnivores. The diet of the vegetarian children more closely resembled current recommendations although they need to be as vigilant as omnivores to reduce their intake of fat, and care is needed to ensure optimal iron status. The results of this study suggest that vegetarian children who include dairy products grow at least as well as those children who eat meat.

The thesis makes a contribution to the debate on the relationship between cultural consumption, cultural taste preferences and class. This field is well researched, but there is no consensus on the relationship between these variables. That cultural consumption is patterned by social status in society is one of the most fundamental insights of cultural sociology. Pierre Bourdieu’s Distinction: A social criticism of the taste assessment (1984) is a central work in the field. Over time, however, Bourdieu's vision has come to be questioned by various empirical findings. The questioning comes, among other findings, from Peterson's (2005) coinage of the cultural omnivore. Defining the cultural omnivore is an increased range of cultural preferences and a will to mix hierarchical cultural preference boundaries. The purpose of the thesis was to fill some of the gaps described by earlier research and seek out how the relations take shape in a Swedish student context. The questions the essay sought to answer were; how does the relationship looks between cultural consumption and class among Swedish students; how does the cultural omnivore reason about his or her wide taste preference; is distinctions among cultural omnivores present and how does it look? Through Exploratory sequential mixed-method, 10 interviews were conducted to later develop a survey that sought to generate some of the results that emerged in the interviews. The result shows that distinction seems to prevail in how cultural products are consumed rather than what is consumed. No clear links between cultural capital and consumption patterns were demonstrated in the results of the survey. The interviews however showed a strong link between cultural capital and how something is consumed, understood and appreciated.
Denna uppsats gör ett inlägg i debatten om relationen mellan kulturell konsumtion, kulturella smakpreferenser och klass. Det aktuella fältet är väl beforskat, men det råder ingen konsensus kring relationen mellan dessa variabler. Att kulturell konsumtion är mönstrat av social ställning i samhället är en av de mest grundläggande insikterna i kultursociologi. Pierre Bourdieus Distinction: a social critique of the judgement of taste (1984) är ett centralt verk inom fältet. Med tiden har dock Bourdieus bild kommit att ifrågasättas av olika empiriska fynd. Ifrågasättandet kommer från bland annat Petersons (2005) myntande av den kulturella allätaren (the cultural omnivore). Vad som definierar den kulturella allätaren är en ökad bredd av kulturella preferenser och en vilja att blanda hierarkiska kulturella genregränser. Syftet var att fylla några av de luckor som beskrivits av annan forskning och söka hur det ser ut i en svensk studentkontext. Frågeställningarna uppsatsen sökte besvara var; hur ser relationen ut mellan kulturell konsumtion och klass bland svenska studenter; hur resonerar den kulturella allätaren kring sin breda smakpreferens; är särskiljning (distinction) bland kulturella allätare närvarande och hur ser den i så fall ut? Genom Exploratory sequential mixed-method genomfördes 10 intervjuer för att sedan utveckla en enkät som sökte generalisera några av de resultat som framkommit i intervjuerna. Resultatet pekar på att särskiljning främst tycks råda i hur man konsumerar kulturella produkter snarare än vad man konsumerar. Inga tydliga kopplingar mellan kulturellt kapital och konsumtionsmönster påvisades i enkäten. Intervjuerna påvisade dock en stark koppling mellan kulturellt kapital och hur något konsumeras, förstås och tas in.

Bakgrund Det finns många olika motiv till att individer väljer att äta växtbaserat. De främsta motiven är egenhälsan och etiska aspekter i form av djurrätt, men även minskad klimatpåverkan. Den största barriären till att övergå till en mer växtbaserad kosthållning är informationsbrist om kosthållningen. Näringsinnehållet skiljer sig mellan mejeriprodukter och växtbaserade alternativ, vilket kan leda till brister om mejeriprodukter helt eller delvis utesluts ur kosten. Syfte Syftet med studien var att undersöka skillnader i attityd och kunskap om mejeriprodukter kontra växtbaserade alternativ hos unga vuxna i åldrarna 18–30 år. Metod Studien var kvantitativt designad och genomfördes via webbenkät i september 2020 med 125 deltagare. Enkäten innehöll bakgrundsfrågor, kunskap- och attitydpåståenden. Data analyserades med IBM SPSS Statistics 27. Signifikansnivån p <0,05 valdes.  Resultat 117 svar analyserades, majoriteten var kvinnor, personer mellan 18–24 år och kosthållningen blandkost. Signifikanta skillnader sågs för påståendena om hälsa, etik och smak mellan kosthållningarna blandkost och vegetarian (p=0,011, p=0,023, p<0,001) samt blandkost och vegan (p<0,001, p=0,042, p=0,008). Samtliga kosthållningar var över lag mer benägna att hålla med om de påståenden som var positivt vinklade för deras kosthållning. 50-87 % svarade fel eller vet ej på kunskapspåståendena, förutom på påståendet Kalcium förekommer naturligt i mejeriprodukter där majoriteten svarade rätt. Inga signifikanta skillnader sågs mellan åldersgrupperna gällande kunskap och attityder. Slutsats Attityderna till mejeriprodukter kontra växtbaserade alternativ skiljer sig beroende på kosthållning, framförallt mellan omnivorer och veganer. Kunskapen om näringsmässiga skillnaderna mellan mejeriprodukter och växtbaserade alternativ var låg hos blandkost och pescetarian och vegetarian och vegan.
Background The motives for consuming plant-based diet vary, the main ones being health related and animal-welfare. Decreasing environmental impact also ranks quite high. The biggest perceived barrier to follow a plant-based diet is the lack of information regarding the diet. The nutritional content of plant-based dairy-alternatives differs from dairy-products. If dairy-products are partially or completely excluded from the diet there is a risk of nutritional deficiencies. Objective The aim of the study was to investigate the difference in attitude towards and knowledge of dairy-products and plant-based alternatives in 18-30-year-olds. Method A web-based survey was conducted in September of 2020 with 125 participants. The survey consisted of three sections with questions regarding background, knowledge of nutritional differences and attitudes towards dairy-products and plant-based alternatives. The data was analysed through IBM SPSS Statistics 27. The significance level was set to p<0,05. Results 117 participants' answers were in the final analysis. Most of them were women and omnivorous. Significant differences in attitude towards health, ethical aspects and taste preferences could be seen between omnivores and vegetarians (p=0,011, p=0,023, p<0,001) as well as omnivores and vegans (p<0,001, p=0,042, p=0,008). In general, the different dietary preferences were prone to agree with statements that agreed with their diet. 50-87% answered incorrectly or “Don’t know” at the knowledgestatements, except Calcium naturaly occurs in dairy products where the majority answered correctly. No significant differences were found between the age groups regarding knowledge or attitude. Conclusion Attitudes towards dairy-products and plant-based dairy-alternatives significantly differ depending on diet. The biggest differences were seen between omnivores and vegans. Knowledge about the nutritional differences between dairy-products and plant-based dairy-alternatives was low among both omnivore and pescatarian and vegetarian and vegan.

L’invasion des écosystèmes par les espèces invasives est vue comme l’une des plus importantes sources de perte de la biodiversité. La meilleure réponse à ces effets est presque toujours le contrôle, ou bien lorsque cela est possible l’éradication de tous les individus de la population invasive. Dans beaucoup de cas, l’élimination de l’espèce invasive est suivie par un rapide et spectaculaire rétablissement des populations locales. Cependant, la disparition soudaine de l’espèce invasive peut générer plusieurs déséquilibres, entraînant des dommages similaires ou encore plus importants sur l’écosystème. Ces phénomènes sont appelés « effets surprises ». Etant donné le nombre et la complexité des interactions entre espèces, il est toujours difficile de prédire les résultats de la suppression d’espèces clés, comme les prédateurs supérieurs. Cela justifie l’importance des études pré-éradication au préalable pour initier l’éradication de l’espèce invasive, afin d’éviter toute catastrophe écologique. Ce projet concerne l’étude de la place des espèces invasives dans les réseaux trophiques envahis, afin de prédire et donc d’éviter les potentielles réactions en chaîne qui pourraient découler de la suppression soudaine de l’espèce invasive. La mise en place de cette méthodologie est basée sur une combinaison d’études empiriques de travail de terrain, d’études de régimes alimentaires classiques et d’isotopes stables en laboratoire et de modélisation mathématique. La partie terrain de mon projet est basée sur un inventaire floristique et faunistique complet de la communauté locale, la détermination des relations trophiques et d’une campagne d’éradication d’une espèce invasive. Le site d’étude sélectionné est l’île Surprise, dans le récif d’Entrecasteaux, en Nouvelle Calédonie, qui est un site de ponte majeur de tortues et d’oiseaux marins, mais aussi un écosystème riche qui est envahi par le rat noir. Mon étude souligne l’importance de considérer les espèces invasives au sein des communautés, pour prendre en compte tous les liens avec les autres espèces, qu’elles soient exotiques ou indigènes. Je montre aussi les avantages et les limites de l’utilisation des analyses en isotopes stables pour la reconstruction du régime alimentaire et des réseaux trophiques. Finalement, j’insiste sur l’impact des rats introduits sur l’île Surprise et la nécessité de l’éradiquer, tout en prenant garde à minimiser l’impact sur les espèces non visées par l’éradication et le risque de déclenchement d’une relâche des plantes exotiques, des fourmis ou des souris
The invasion of ecosystems by exotic species is viewed as one of the most important sources of biodiversity loss. The best response to these effects is almost always to control the alien population, when possible by eradicating the whole alien population from the island. In many cases, the elimination of the alien invasive species is followed by a rapid and often spectacular recovery of the impacted local populations. However, the sudden removal of the alien species may generate further disequilibria, resulting in similar or greater damages to the ecosystem. This has been called the "surprise effect"; Given the numerous and often complex population interactions among species, it is difficult to predict the outcome of the removal of key species, such as a top predator. This justifies a careful pre-control study prior to initiating the eradication of alien species eradication, in order to avoid an ecological catastrophe. This project concerns the study of the place of invasive species in invaded trophic webs in order to predict, and thus avoid, potential chain reactions that could be triggered by alien species sudden removal. The setting of this methodology is based on a combination of empirical work in the field, classical diet and stable isotope analyses in the lab, and mathematical modelling. The field part of my project is based on a complete floristic and faunistic inventory of the local communities, the determination of the resulting trophic webs and an invasive species eradication campaign. The selected field site is Surprise Island, in the Entrecasteaux reef, New Caledonia, a major breeding site for sea turtles and seabirds, and a rich ecosystem that is invaded by black rats. My study highlights the importance of considering the invasive species within the invaded communities, taking into account all link with other species, be they exotic or indigenous. I also show the advantages and limits of using stable isotope analyses for the reconstruction of diet composition and trophic webs. Finally, I stress out the impact of the rats introduced on Surprise island, and the need to eradicate them, while taking care of minimising both the impact on non-target species and the risks of triggering a release of exotic plants, ants or mice

O fornecimento de colostro bovino liofilizado (CBL), fonte alternativa de proteína, foi avaliado como um ingrediente inovador na nutrição de peixes. A influência desta secreção láctea foi estudada sobre o desenvolvimento dos tecidos entérico, hepático e muscular de pacu (Piaractus mesopotamicus) e dourado (Salminus brasiliensis) juvenis, utilizando-se análises da concentração sérica de IGF-I, o estudo da estrutura morfológica e atividade enzimática no intestino e, os indicadores de atividade celular nos tecidos entérico, hepático e muscular. Os pacus (8,5 ± 0,7g; 7,7 ± 0,3cm) e dourados (13,3 ± 0,9g; 10,8 ± 0,3cm), foram distribuídos num delineamento experimental inteiramente casualizado em esquema fatorial 3x2, constituindo-se de três dietas com inclusão de CBL (0%, 10% e 20%) e dois períodos experimentais (30 e 60 dias). Para os indicadores de desempenho no pacu, houve interação para ganho de peso (GP) e conversão alimentar aparente (CAA) (P<0,05). Os valores de GP, para 10 e 20% de CBL, não diferiram do 0% de CBL, indicando que as dietas foram adequadas e atenderam as necessidades nutricionais dos juvenis. Maior índice de conversão alimentar foi encontrado com 10% de CBL, aos 60 dias. A concentração de IGF-I não diferiu entre as dietas nas duas espécies, contudo, foi maior no dourado aos 60 dias (P<0,05). A morfologia do epitélio intestinal de pacu e dourado juvenis não foi alterada pelo fornecimento de CBL, entretanto, observaram-se diferenças entre os segmentos intestinais. A atividade da enzima aminopeptidase N foi maior nos pacus alimentados com 10% e 20% de CBL (P<0,05); a atividade das peptidases e dissacaridases foi menor aos 60 dias; exceto para aminopeptidase A, que apresentou elevada atividade neste mesmo período. No dourado, apenas houve diferença para aminopeptidase A, que foi menor aos 60 dias (P<0,05). Com relação aos indicadores de atividade celular, no intestino de pacu, a relação proteína total (PT)/RNA foi menor aos 30 dias. No fígado de dourado houve interação entre dieta e período para DNA, sendo maior nos peixes alimentados com 20% de CBL, aos 60 dias. No músculo de pacu PT/RNA foi maior com 10% de CBL; RNA, PT/DNA e RNA/DNA menor aos 60 dias, enquanto DNA e PT/RNA, maior neste mesmo período. No músculo do dourado, RNA e RNA/DNA, foram menores aos 60 dias e, PT/RNA, maior neste mesmo período (P<0,05). Considerando os aspectos estudados para avaliar as consequências do fornecimento de colostro bovino para pacu e dourado juvenis, observou-se que foram mantidas inalteradas a plasticidade e atividade das enzimas no epitélio intestinal e a atividade celular nos tecidos entérico, hepático e muscular. Esta condição sugere a possibilidade de uso desta secreção láctea na nutrição dos peixes estudados.
The supply of lyophilized bovine colostrum (LBC), alternative protein source, has been evaluated as an innovative ingredient in fish nutrition. The milk secretion influence was studied on enteric, liver and muscle tissues development of pacu (Piaractus mesopotamicus) and dourado (Salminus brasiliensis), using analysis of serum IGF-I concentration, morphological structure study and enzyme activity in intestine, as well as the responses of cellular indicators in enteric, liver and muscle tissues. Juveniles of pacu (8.5 ± 0.7g; 7.7 ± 0.3cm) and dourado (13.3 ± 0.9g; 10.8 ± 0.3cm) were distributed in a completely randomized design in a factorial scheme 3x2, constituting of three diets with LBC inclusion (0, 10 or 20%) and two experimental periods (30 or 60 days). The performance indicators in pacu, interaction between diet and period was observed to weight gain (WG) and feed conversion rate (FCR) (P<0.05). GP values in 10 and 20% LBC did not differ from the values of 0% LBC, indicating that the diets were adequate and met the nutritional needs of the juveniles. Higher FCR was found with 10% LBC at 60 days. IGF-I concentration did not differ between diets in both species, but was higher in dourado at 60 days (P<0.05). The pacu and dourado intestinal epithelium histomorphometry, was not altered by the LBC supply, however, there were differences between intestinal segments. The enzyme activity of aminopeptidase N was higher in pacu fed 10% and 20% of LBC (P<0.05); the activity of peptidases and disaccharidases was lower at 60 days; except for aminopeptidase A which showed high activity in this period. In the dourado, was difference only to aminopeptidase A, which was lower at 60 days (P<0.05). Regarding the indicators of cellular activity, in intestine of pacu, total protein (TP)/RNA ratio was lower at 30 days. In liver of dourado, there was interaction between diet and period for DNA, being higher in fish fed 20% LBC, at 60 days. In muscle of pacu, TP/RNA was higher with 10% LBC; RNA, TP/DNA and RNA/DNA ratio lower at 60 d, while TP and DNA/RNA ratio increased during the same period. In muscle of dourado, RNA and RNA/DNA were lower at 60 days and, TP/RNA higher in the same period (P<0.05). Considering the aspects studied to evaluate the effects of bovine colostrum for juvenile pacu and dourado, it was observed that were kept unchanged the plasticity and enzymes activity in intestinal epithelium and cellular activity in enteric, liver and muscle tissues. This condition suggests the possibility of using this milk secretion in nutrition of fish studied.

Le lac de Tonlé Sap (TSL), Cambodge, est un écosystème lac-rivière de forêt alluviale au régime d'écoulement alternatif. Le lac est un déversoir lors de l'inondation saisonnière du Mékong et sert de réservoir en période de basses eaux. La superficie du lac pendant la saison sèche (février à mai), est d'environ 2 700 km2 pour une profondeur d'environ 1 mètre. Cette superficie est pratiquement multipliée par six quand arrive la saison des pluies, pour atteindre près de 16 000 km2 et une profondeur de 9 mètres, noyant rizières et forêts. C'est le plus grand lac d'eau douce d'Asie du Sud-Est. C'est aussi l'une des zones de pêche d'eau douce les plus importantes et productives du monde avec près de 75% du volume annuel de pêche en eau douce du Cambodge, ce qui permet la survie de près de 2,5 millions de personnes. Les changements saisonniers du cycle hydrologique ont une influence sur la structuration des communautés de poissons à l'échelle temporelle et spatiale, mais aussi sur les comportements trophiques des principales espèces qui n'exploitent alors pas les mêmes habitats. Toutefois, le bassin versant du Mékong est en changement constant avec un développement important des infrastructures en lien avec l'eau : production d'hydro-électricité, besoins important en irrigation, maitrise des inondations, eau potable, ... Les changements climatiques accélèrent les modifications du cycle hydrologique annuel. Il est alors supposé que ces modifications ont des effets forts sur les habitats et les proies disponibles et finalement sur la biodiversité, notamment de l'ichtyofaune et sur l'abondance des poissons disponibles pour les pêcheries.Dans un premier temps, nous avons caractérisé les variations spatio-temporelles de la composition taxonomique des poissons et mis en lumière quels sont les déterminants de ces variations. À cette fin, nous avons estimé la diversité bêta comme la variance totale de la matrice site par communauté d'espèce et l'avons divisée en contribution locale à la diversité bêta (LCBD) et contribution des espèces à la diversité bêta (SCBD). Nous avons ensuite effectué plusieurs régressions linéaires pour déterminer si la richesse taxonomique, l'abondance des espèces et le niveau de l'eau expliquaient la variation temporelle de la contribution du site et de l'espèce à la diversité bêta. Nos résultats indiquent une forte variation temporelle de la diversité bêta due aux contributions différentielles des sites et des espèces à la variation spatiale de la composition taxonomique des poissons. Nous avons également constaté que la direction, la forme et l'effet relatif de la richesse spécifique, de l'abondance et du niveau de l'eau sur la variation temporelle des valeurs LCBD et SCBD varient grandement selon les sites. Ces résultats suggèrent ainsi une variation spatiale des processus conduisant à une variation temporelle de la composition de la communauté. Dans l'ensemble, nos résultats suggèrent que la composition taxonomique des poissons n'est pas distribuée de manière homogène dans l'espace et dans le temps et risque d'être affectée à l'avenir si la dynamique saisonnière d'écoulement du système est altérée par les activités humaines et/ou les changements climatiques. Dans un second temps, nous avons cherché à étudier le modèle d'évolution temporel des principales espèces en terme d'occurrence et d'abondance à travers le cycle saisonnier hydrologique
The Tonle Sap Lake (TSL), Cambodia, is a flood-pulse system. It is the largest natural lake in South- East Asia and constitutes one of the largest fisheries over the world, supporting the livelihood 2.5 million peoples. Seasonal change in annual hydrological cycle appears to have influence on fish community structure, both spatial and temporal variation, particularly on feeding behavior of TSL's fishes. Nonetheless, the Mekong River Basin is changing rapidly due to accelerating water infrastructure development (hydropower, irrigation, flood control, and water supply) and climate change, bringing considerable modifications to the annual flood-pulse of the TSL. Such modifications are expected to have strong impacts on fish biodiversity, abundance, reduced habitat and food availability within the lake. To invest how TSL's fish community structure responds to the seasonal change, how they shift their diet across hydrological cycles and feeding competing for food resource: First, we aim to characterize the spatio-temporal variations of fish taxonomic composition and to highlights the underlying determinants of these variations. For this purpose, we estimated beta diversity as the total variance of the site-by-species community matrix and partitioned it into Local Contribution to Beta Diversity (LCBD) and Species Contribution to Beta Diversity (SCBD). We then performed multiple linear regressions to determine whether species richness, species abundances and water level explained the temporal variation in the contribution of site and species to beta diversity. Our results indicate strong temporal variation of beta diversity due to differential contributions of sites and species to the spatial variation of fish taxonomic composition. We further found that the direction, the shape and the relative effect of species richness, abundances and water level on temporal variation in LCBD and SCBD values greatly varied among sites, thus suggesting spatial variation in the processes leading to temporal variation in community composition. Overall, our results suggest that fish taxonomic composition is not homogeneously distributed over space and time and is likely to be impacted in the future if the flood-pulse dynamic of the system is altered by human activities. Second, we aim to investigate the temporal pattern of the most occurrence and abundance species and how their co-occurrence pattern across hydrological cycles. We found that occurrence and abundance patterns were temporally varied at all water level seasons. Strong temporal variation in species occurrence was occurred with visiting species such as Labiobarbus leptocheilus and Poropuntius deauratus while water level starts to fill into the TSL. We further observed that the abundance of 17 species was strongly varied while other 22 species (mainly TSL's residential species) were stable within the year. Positive species co-occurrence pattern was generally higher than negative species co-occurrence at all water level seasons. Highest positive co-occurrence patterns were found during the period of decrease and low water level seasons while fishes are migrating from flooded areas, competing for resource and habitats during low water season. Study on temporal distribution and species co-occurrence of fish and how community responds to the seasonal change in hydrological cycles provides critical information for fisheries management and conservation in the Tonle Sap Lake (TSL) as well as maintaining fish biodiversity in the Mekong system. Third, the implications of seasonality on food web structure have been notoriously understudied in empirical ecology, particularly in TSL's system. The current study, we focus on seasonal changes in one key attribute of a food web, vertical trophic position of consumers

Die paläarktische omnivore Weichwanze Dicyphus errans Wolff (Heteroptera, Miridae, Bryocorinae) zeichnet sich durch ein ausgesprochen breites Spektrum an besetzten Wirtspflanzen und konsumierten Beutetieren aus. Über 150 von D. errans akzeptierte Pflanzenarten sind erstmalig belegt worden. Der erfolgreiche Verzehr von 15 Beute-tierarten wurde quantitativ nachgewiesen. Eine weitere Besonderheit der Wanze besteht in der Präferenz für glandulär behaarte Pflanzen. Die Weichwanze besetzt somit von vielen anderen Insekten gemiedene Nischen. Untersuchungen im Botanischen Garten der Technischen Universität Dresden (2000 bis 2002) ließen auf eine bemerkenswerte räuberische Aktivität und Anpassungsfähigkeit an unterschiedliche Habitate, Beutetiere und Klimabedingungen schließen. Die fortführenden Studien im Rahmen der vorliegenden Dissertation (2002 bis 2005) erbrachten umfassende Erkenntnisse über die Art D. errans im Hinblick auf deren Morphologie, Vermehrung und Haltung, Bionomie und Ökologie (Fekundität und Ontogenese in Abhängigkeit von ausgewählten Einflussfaktoren, Dormanz), Aufenthalt und Fortbewegung (räumliche Orientierung und strukturanalytische Studien zu den Interaktionen zwischen Wanze und Pflanzenoberflächen), den Nahrungserwerb (Verzehrleistung und Omnivorie) sowie Videodokumentationen der Lebensweise und des Verhaltens. Der Generalist und Opportunist D. errans integriert sich als Pflanzensaftsauger regulierendes Kompartiment neben echten Räubern und Parasitoiden in Biozönosen. Als omnivores Insekt übernimmt die Wanze eine intermediäre und supplementäre Position in Nahrungsnetzen. Die Lebensweise dieser Weichwanzenart erscheint sehr komplex. Die enge Assoziation mit Pflanzen tritt stark in den Vordergrund. Sie ist in jeglichen Betrachtungen von D. errans unbedingt zu berücksichtigen und bietet außerdem als ein Modellsystem ein spannendes Forschungsfeld im Hinblick auf die Adaptation partiell räuberisch lebender Insekten an behaarte Pflanzen
The omnivorous mirid bug Dicyphus errans Wolff (Heteroptera, Miridae, Bryocorinae) lives on a wide range of host plants and feeds on various preys. Over 150 plant species accepted by the mirid bug have been identified. It was experimentally shown that 15 prey species are efficiently consumed. Another characteristical features of D. errans is that it preferes hairy plants. Thus, the mirid bug occupies unique niches avoided by many other insects. Investigations, carried out at the Botanical Garden of the Technical University of Dresden (2000-2002) gave evidence for a remarkable predatory activity and ability to adaptation to different habitats, preys and climate conditions. The studies presented in the dissertation (2002-2005) gave the comprehensive knowledge about the species D. errans, especially its morphology, rearing, bionomy and ecology (fecundity and ontogenesis depending on selected factors, dormancy), habitat preference and locomotion (spatial orientation and structural-analytical studies of the interactions between the bug and plant surfaces), foraging and food ingestion (predatory capacity and omnivory). In addition, video documentation of the modus vivendi and the behavior was performed. The generalist and opportunist D. errans lives together with predators and parasitoids and takes part in a biological control of phytophagous insects in biocenoses. The life history of this bug species appeared to be very complex. The close association to plants has to be considered. Dicyphus errans offers a model system for further research on omnivorous predatory insects connected with hairy plants

Die paläarktische omnivore Weichwanze Dicyphus errans Wolff (Heteroptera, Miridae, Bryocorinae) zeichnet sich durch ein ausgesprochen breites Spektrum an besetzten Wirtspflanzen und konsumierten Beutetieren aus. Über 150 von D. errans akzeptierte Pflanzenarten sind erstmalig belegt worden. Der erfolgreiche Verzehr von 15 Beute-tierarten wurde quantitativ nachgewiesen. Eine weitere Besonderheit der Wanze besteht in der Präferenz für glandulär behaarte Pflanzen. Die Weichwanze besetzt somit von vielen anderen Insekten gemiedene Nischen. Untersuchungen im Botanischen Garten der Technischen Universität Dresden (2000 bis 2002) ließen auf eine bemerkenswerte räuberische Aktivität und Anpassungsfähigkeit an unterschiedliche Habitate, Beutetiere und Klimabedingungen schließen. Die fortführenden Studien im Rahmen der vorliegenden Dissertation (2002 bis 2005) erbrachten umfassende Erkenntnisse über die Art D. errans im Hinblick auf deren Morphologie, Vermehrung und Haltung, Bionomie und Ökologie (Fekundität und Ontogenese in Abhängigkeit von ausgewählten Einflussfaktoren, Dormanz), Aufenthalt und Fortbewegung (räumliche Orientierung und strukturanalytische Studien zu den Interaktionen zwischen Wanze und Pflanzenoberflächen), den Nahrungserwerb (Verzehrleistung und Omnivorie) sowie Videodokumentationen der Lebensweise und des Verhaltens. Der Generalist und Opportunist D. errans integriert sich als Pflanzensaftsauger regulierendes Kompartiment neben echten Räubern und Parasitoiden in Biozönosen. Als omnivores Insekt übernimmt die Wanze eine intermediäre und supplementäre Position in Nahrungsnetzen. Die Lebensweise dieser Weichwanzenart erscheint sehr komplex. Die enge Assoziation mit Pflanzen tritt stark in den Vordergrund. Sie ist in jeglichen Betrachtungen von D. errans unbedingt zu berücksichtigen und bietet außerdem als ein Modellsystem ein spannendes Forschungsfeld im Hinblick auf die Adaptation partiell räuberisch lebender Insekten an behaarte Pflanzen.
The omnivorous mirid bug Dicyphus errans Wolff (Heteroptera, Miridae, Bryocorinae) lives on a wide range of host plants and feeds on various preys. Over 150 plant species accepted by the mirid bug have been identified. It was experimentally shown that 15 prey species are efficiently consumed. Another characteristical features of D. errans is that it preferes hairy plants. Thus, the mirid bug occupies unique niches avoided by many other insects. Investigations, carried out at the Botanical Garden of the Technical University of Dresden (2000-2002) gave evidence for a remarkable predatory activity and ability to adaptation to different habitats, preys and climate conditions. The studies presented in the dissertation (2002-2005) gave the comprehensive knowledge about the species D. errans, especially its morphology, rearing, bionomy and ecology (fecundity and ontogenesis depending on selected factors, dormancy), habitat preference and locomotion (spatial orientation and structural-analytical studies of the interactions between the bug and plant surfaces), foraging and food ingestion (predatory capacity and omnivory). In addition, video documentation of the modus vivendi and the behavior was performed. The generalist and opportunist D. errans lives together with predators and parasitoids and takes part in a biological control of phytophagous insects in biocenoses. The life history of this bug species appeared to be very complex. The close association to plants has to be considered. Dicyphus errans offers a model system for further research on omnivorous predatory insects connected with hairy plants.

The thesis examines the dynamics of intraguild predation models incorporating adaptive behaviour. The top predator varies its relative consumption of the intermediate consumer and the basal resource. The consumer alters its activity level in response to the threat of predation. Incorporating these adaptive behaviours facilitated three species coexistence, but restricted omnivory by promoting the formation of three species food chains. Model modifications which promoted omnivory also tended to reduce three species coexistence. It is predicted that omnivory should be most common when the intermediate and the basal species are similarly profitable to the predator. The model also predicts two types of omnivory. Strong omnivory occurs when the predator always consumes intermediate amounts of both prey items. Weak omnivory occurs when the predator preys almost exclusively on one prey at most times, but rapidly switches to include the other when the relative abundance of that second prey exceeds a certain level.