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Rate, Stephen R., and n/a. "Invertebrate diversity and vegetation heterogeneity : plant-invertebrate relationships in indigenous New Zealand grasslands." University of Otago. Department of Botany, 2005. http://adt.otago.ac.nz./public/adt-NZDU20061025.144447.
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Spatial heterogeneity of the environment, as measured by floral diversity, composition and structure, is known to influence the distribution and diversity of invertebrates. Heterogeneity brought about by anthropogenic disturbance may be a threat to invertebrate diversity. This thesis investigates the impacts of vegetation heterogeneity at a range of scales on the diversity of invertebrate populations in modified high-altitude indigenous grasslands on the Rock and Pillar Range, Central Otago.
Invertebrates were sampled in and on the edges of snow tussock fragments to assess whether species richness increased systematically with fragment area. Invertebrate composition was poorly related to fragment area, plant composition and environmental variables. Taxon richness, abundance and/or diversity for three invertebrate groups increased as fragment area decreased, perhaps reflecting an influx of species from the surrounding matrix. For snow tussock leaf invertebrates in autumn, richness and abundance were at least two times lower in tussocks exposed to the wind than those in the centre of fragments, suggesting selection of habitat may be based on microclimatic characteristics.
Invertebrates were sampled from the bases of tussocks after they were clipped to simulate three levels of vertebrate grazing. Invertebrate community composition differed between sites and sampling dates but was unaffected by clipping treatment. At the higher altitude site invertebrate abundance was 1.45 times greater and Shannon-Wiener diversity (H�) 1.22 times lower than at the lower altitude site. The latter sampling date had higher abundance (2.12 times) and taxon richness (1.14 times) than the earlier date.
Pitfall-trapped invertebrates in cushionfield, herbfield and snow tussock differed in community composition and often by taxon richness, abundance and diversity. Across habitats, plant composition, plant diversity and some environmental variables were correlated with invertebrate variables, but could not be separated from vegetation type.
The invertebrates collected in the course of the study are listed. Four Phyla, eight Classes, 24 orders and over 300 taxa were recorded. Almost all taxa are endemic and many have limited distributions and/or are undescribed. A species list is provided with collection altitude, method and habitat type.
Invertebrate assemblages from sites differing in altitude, vegetation type and level of habitat modification on the Rock and Pillar Range are compared. Sites differed in species composition and rank orders of abundance and richness. At lower elevations, invertebrate richness was at least 25% less, and standardised trap abundance at least 44% less, than that at the highest elevation. Richness and abundance of exotic invertebrates decreased with increasing altitude.
This thesis highlights several points concerning the study of grassland invertebrates and heterogeneity on the Rock and Pillar Range. First, there are differences in invertebrate assemblages at a range of scales. Conserving invertebrate diversity will therefore require altitudinal sequences and different habitat types, including disturbed areas. At high elevations, tussock habitat may be disproportionately important due to its relative rarity. Second, the effects of disturbance on invertebrates were only visible at large spatial scales. Third, there is a paucity of research on New Zealand invertebrates, especially in regard to terrestrial disturbance, which has resulted in a shortfall of biological, distributional, taxonomic and ecological knowledge.
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Pryke, James Stephen. "Conservation of the invertebrate fauna on the Cape Peninsula." Thesis, Link to the online version, 2008. http://hdl.handle.net/10019/1452.
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Marçal, Sandra Francisca [UNESP]. "Efeito de alterações do nível da água do reservatório Salto Grande, usadas para o controle de macrófitas, na estrutura e estabilidade da fauna de invertebrados fitófilos em uma lagoa marginal ao Rio Paranapanema." Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/116034.
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Em ambientes aquáticos controlados por barragens, a elevada estabilidade hídrica favorece a proliferação de macrófitas, sendo para seu controle utilizado um manejo por alterações no nível da água. Porém não existem estudos que avaliem o efeito dessa técnica, que gera condições extremas de seca e inundação sobre a fauna de invertebrados fitófilos. O presente trabalho foi realizado durante alterações operacionais do nível da água para controle de macrófitas submersas no reservatório de Salto Grande (SP/PR). O objetivo foi avaliar o efeito dessas alterações sobre a diversidade de invertebrados associados à macrófita Egeria na lagoa Pedra Branca, conectada ao Rio Paranapanema e sob a influência do reservatório. As coletas foram realizadas ao longo de um transecto longitudinal da lagoa, antes do manejo ser iniciado (controle), no 1º, 7º e 11º dias após o rebaixamento (PR), quando a lagoa se desconecta do rio, e 49 dias após o enchimento do reservatório (PE). A hipótese do trabalho de menor diversidade após as alterações do nível da água do reservatório (seca e cheia induzidas) foi avaliada ao nível de toda a fauna e para os táxons de Chironomidae. As alterações do nível da água foram acompanhadas por alterações na estrutura da fauna fitófila, com variação temporal na densidade dos grupos, especialmente de Hexapoda, Mollusca e Protozoa. As mudanças ambientais relacionadas à contração (seca), e conseqüente concentração das macrófitas na área central da lagoa, e ampliação (cheia) das regiões limnética e litorânea geraram uma substituição de grupos dominantes (reduzindo a densidade de Chironomidae e aumentando a de Physa marmorata durante o PR), aumento na riqueza e maior diversidade e equitabilidade no PE. Os distúrbios causaram redução na densidade das três subfamílias de Chironomidae, principalmente de Chironominae, com maior riqueza e dominância em todas as datas ...
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Marçal, Sandra Francisca. "Efeito de alterações do nível da água do reservatório Salto Grande, usadas para o controle de macrófitas, na estrutura e estabilidade da fauna de invertebrados fitófilos em uma lagoa marginal ao Rio Paranapanema /." Botucatu, 2014. http://hdl.handle.net/11449/116034.
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Orientador: Virgínia Sanches UiedaBanca: Ana Lúcia Brandimarte
Banca: Marcelo Luiz Martins Pompêo
Banca: Alaíde Aparecida Fonseca Gessner
Banca: Marcos Gomes Nogueira
Resumo: Em ambientes aquáticos controlados por barragens, a elevada estabilidade hídrica favorece a proliferação de macrófitas, sendo para seu controle utilizado um manejo por alterações no nível da água. Porém não existem estudos que avaliem o efeito dessa técnica, que gera condições extremas de seca e inundação sobre a fauna de invertebrados fitófilos. O presente trabalho foi realizado durante alterações operacionais do nível da água para controle de macrófitas submersas no reservatório de Salto Grande (SP/PR). O objetivo foi avaliar o efeito dessas alterações sobre a diversidade de invertebrados associados à macrófita Egeria na lagoa Pedra Branca, conectada ao Rio Paranapanema e sob a influência do reservatório. As coletas foram realizadas ao longo de um transecto longitudinal da lagoa, antes do manejo ser iniciado (controle), no 1º, 7º e 11º dias após o rebaixamento (PR), quando a lagoa se desconecta do rio, e 49 dias após o enchimento do reservatório (PE). A hipótese do trabalho de menor diversidade após as alterações do nível da água do reservatório (seca e cheia induzidas) foi avaliada ao nível de toda a fauna e para os táxons de Chironomidae. As alterações do nível da água foram acompanhadas por alterações na estrutura da fauna fitófila, com variação temporal na densidade dos grupos, especialmente de Hexapoda, Mollusca e Protozoa. As mudanças ambientais relacionadas à contração (seca), e conseqüente concentração das macrófitas na área central da lagoa, e ampliação (cheia) das regiões limnética e litorânea geraram uma substituição de grupos dominantes (reduzindo a densidade de Chironomidae e aumentando a de Physa marmorata durante o PR), aumento na riqueza e maior diversidade e equitabilidade no PE. Os distúrbios causaram redução na densidade das três subfamílias de Chironomidae, principalmente de Chironominae, com maior riqueza e dominância em todas as datas ...
Abstract: Not available
Doutor
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Jordan, Kyle K. "The effects of landscaping mulch on invertebrate populations and soil characteristics." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1092784271.
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Jordan, Kyle Kenton. "The effects of landscaping mulch on invertebrate populations and soil characteristics." Connect to this title online, 2004. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1092784271.
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Thesis (Ph. D.)--Ohio State University, 2004.Title from first page of PDF file. Document formatted into pages; contains x, 83 p.; also includes graphics (some col.). Includes bibliographical references (p. 77-83). Available online via OhioLINK's ETD Center
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Simpson, Ian Charles. "The impact of agricultural practices on the aquatic invertebrate populations of ricefields." Thesis, Cardiff University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274018.
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Ojala, Jeffrey Veikko. "Invertebrate phenology and prey selection of three sympatric species of Salmonids." Connect to this title online, 2008. http://scholarworks.umass.edu/theses/97/.
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Steffan, Shawn Alan. "Biodiversity and fear ecology the cascading effects of species richness and nontrophic interactions /." Pullman, Wash. : Washington State University, 2009. http://www.dissertations.wsu.edu/Dissertations/Spring2009/s_steffan_041709.pdf.
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Hofmann, T. A. "The effects of grassland management on the invertebrate populations of coastal grazing marshes." Thesis, University of Essex, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.412344.
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Hambelton, R. G. "The use of artificial substrates as a method of monitoring estuarine benthic invertebrate populations." Thesis, University of Salford, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372155.
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McKinnon, Jean Fiona, and n/a. "Aspects of the population biology of the southern arrow squid, Nototodarus sloanii, in southern New Zealand." University of Otago. Department of Marine Science, 2007. http://adt.otago.ac.nz./public/adt-NZDU20071204.161531.
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Nototodarus sloanii is an important component of the Southern Ocean fauna, and the basis of a large commercial fishery. Despite this, much is unknown about the biology of this species. This study examines some aspects of the biology of N. sloanii.
Stomach contents analysis identified no significant differences in diet between male and female squid. Sixteen putative species, including 12 identifiable teleosts, 2 crustaceans, and 2 cephalopods were identified in the diet of this species. The euphausid, Nyctiphanes australis was the most important prey item, Lanternfish, Lampanyctodes hectoris, and Pearlside, Maurolicus muelleri, were of secondary importance.
Squid were aged using counts of statolith micro-increments and back-calculation from the date of capture showed that hatching occurred between August and February, with a peak in the austral winter/spring and another smaller peak in the austral summer. Growth rate for male squid differed depending on whether squid were hatched in the winter/spring or summer. Growth rates were more variable in the winter/spring-hatched individuals, and they attained larger size than summer-hatched squid. This was not the case for female squid. Mean age for immature winter/spring-hatched squid was significantly higher than for summer-hatched squid, although there was no significant difference in mean mantle length or body mass. No significant differences between mean age, mantle length, or body mass for same-gender mature squid, regardless of hatch season, were apparent. However, mature female squid hatched in the winter/spring season were significantly longer (ML) than mature male squid hatched in winter/spring. No squid was found to be older than 211 days. All squid had started to mature by 91-120 days old and all were fully mature at 180 days.
Validation experiments run on juvenile squid using calcein markers were inconclusive, however the increments in the statoliths were very similar to those found in other validated species of ommastrephid squid, thus for the purposes of this study they were assumed to be of daily periodicity.
Gladius increments identify a gender difference in growth rate, with female squid having a shorter initial slow growth phase than male squid.
Gonadosomatic indices (GSIs) were calculated for male and female squid. These were low (7.12%�0.3% for females and 1.9%�0.2% for males) suggesting that these squid are intermittent spawners. This is further supported by a histological examination, which found germinal cells of different stages present in the same gonad. Lack of mature individuals in this study means that these results are suggestive rather than definitive; more examination of the reproductive process of this squid is required. Histological examination was also used to validate the Lipinski maturity scale for use with this species, while some misidentification occurred the scale is useful to place squid into the broad categories of immature, maturing, or mature. New maturity scales were created for N. sloanii utilising these broad categories. Finer-scale identification is not possible using this scale, as maturation appears to be a continuous process.
Morphometric measurements were taken from both hard and soft tissues and were analysed using non-metric multidimensional scaling and analysis of similarity. Divisions were only apparent in the hard structure measurements. They did not appear to be age, dietary or reproductive differences.
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Stevens, Peter M. "Host races and cryptic species in marine symbionts." Connect to this title online, 1990. http://hdl.handle.net/2292/2321.
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Schlechte, John Warren. "Stage-structured analysis and modeling of the Pacific razor clam (Siliqua patula) in a changing environment : investigation of population dynamics and harvest strategies using process models and simulation /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/5277.
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Randel, Charles Jack. "Influences of vegetation characteristics and invertebrate abundance of Rio Grande wild turkey populations, Edwards Plateau, Texas." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/1316.
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Since 1970, Rio Grande wild turkey (Meleagris gallapavo intermedia) numbers in the southern region of the Edwards Plateau of Texas have been declining. Nest-site characteristics and invertebrate abundance were hypothesized as limiting wild turkey numbers in declining regions. Wild turkeys were trapped and fitted with mortality-sensitive radio transmitters on 4 study areas; 2 within a region of stable (northern Edwards Plateau) populations, and 2 within a region of declining populations. Monitoring occurred from February 2001 to August 2003. Nest-site locations were determined via homing during the breeding season. Following nesting attempts/completions, nest fate, vegetation height, visual obstruction, litter depth, percent cover, and cover scores of forbs, grass, litter, and bare ground at each nest site and surrounding area were sampled. This was done to determine if wild turkey hens selected nest sites with vegetative characteristics differing from surrounding habitat. Brood survival was calculated as >1 poult surviving to 2-weeks. Broods were followed for 6-weeks post-hatch or to brood failure. Invertebrates were collected, via sweep-net and D-vac, at each visually confirmed brood location and a paired random site to determine if wild turkey hens selected brood habitat based on invertebrate abundance. Analyses were performed to determine if invertebrate abundance differed between study regions. Turkey hens selected nest sites with greater visual obstruction and more litter depth on both regions of stable and declining turkey abundance. No vegetative differences were detected between stable and declining region nest sites. Frequency of Orthoptera was 35 times greater at nest sites on stable regions than declining regions in all 3 years. Orthoptera is a noted food source for young galliformes and comprised the majority of dry mass in invertebrate samples, nest sites and brood locations, on both the stable and declining regions. No differences in total invertebrate dry mass were detected between regional brood locations. Nest-site vegetative characteristics did not alter nest success between regions. The 2 overall objectives of this study were to determine if nest-site vegetation characteristics and invertebrate abundance affected wild turkey numbers in the Edwards Plateau. Regional differences in vegetative characteristics were not detected, thus not likely to be causing differences in turkey numbers between regions. Nest-site invertebrates were found to be 35 times greater at stable region nest sites, possibly giving wild turkey poults from stable regions greater initial chances of survival.
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Reiss, Aya Elaine. "The invertebrate connection : tracing the value of food subsidies from fishless headwaters to downstream fish populations." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/32191.
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The role of ecosystem subsidies from fishless, headwater streams for downstream fish
populations was investigated through multiple approaches in the coastal temperate
rainforest of British Columbia. Terrestrial invertebrate samples were collected in two
streams of differing canopy (broadleaf and coniferous) on a weekly basis to assess
seasonal (spring to fall) terrestrial inputs to headwater streams. Thirty-four fishless
headwater streams were also sampled for both drift and terrestrial input of invertebrates
over two seasons (spring and summer) and two canopy types (broadleaf and coniferous)
to quantify the magnitude of upstream subsidies at different times of year and from
headwaters with different land-use histories. Potential fish growth response to headwater
subsidies was examined both in a feeding experiment and through bioenergetics
modeling. Juvenile cutthroat trout in experimental channels were fed one of seven diets
(0-9% of their biomass) to determine if biomass accumulation was proportional to food
availability. Bioenergetics modeling was used to perform a sensitivity analysis on
parameters influencing fish growth and to validate experimentally-derived growth-response curves. Terrestrial invertebrate inputs increased significantly from May-
September and a significant increase in total invertebrate export was observed from
invertebrates in the drift from May-July. Quantification of subsidies revealed that streams
running through broadleaf canopies exported greater, but not significant, numbers (mean
= 1.73 individuals/m³) and biomass (mean = 1.37 mg/m³) of invertebrates than those
adjacent to coniferous ones (mean = 1.49 individuals/m³ and 1.30 mg/m³ ). Drift
abundance was made up of roughly 83% aquatic and 17% terrestrial invertebrates while biomass was composed of 51% aquatic and 49% terrestrial invertebrates. One-year-old
cutthroat trout demonstrated significantly increased relative growth rates with greater
food abundance. Sensitivity analysis of model parameters identified that variation in the
ratio of terrestrial :aquatic prey caused the greatest change in consumer growth output
response at high prey densities. Using the experimentally-derived fish growth response
curve, measured headwater invertebrate drift densities, and drift densities reported in
local fish-bearing streams, a 12-fold increase in relative growth rate of downstream
consumers exposed to headwater resources was predicted. Findings from this study
highlight the potentially important contributions of food resources from fishless
headwater streams for downstream consumers.Forestry, Faculty of
Graduate
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Turner, Kelley L. Matthews Robin A. "A comparison of benthic macroinvertebrate assemblages among kryal and rhithral lake outlets in the North Cascade Mountains /." Online version, 2009. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=319&CISOBOX=1&REC=1.
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Milakovic, Brian. "Invertebrate populations of intact and degraded areas of a supra-tidal marsh at La Perouse Bay, Manitoba." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ45502.pdf.
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Lynam, Christopher Philip. "Ecological and acoustic investigations of jellyfish (Scyphozoa and Hydrozoa)." Thesis, St Andrews, 2006. https://research-repository.st-andrews.ac.uk/handle/10023/466.
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Miller, Diana M. "EVALUATING A NOVEL ENDOPHYTIC GRASS FOR ITS POTENTIAL TO REDUCE INVERTEBRATE POPULATIONS AND ASSOCIATED BIRD STRIKE RISK AT AIRPORTS." UKnowledge, 2015. http://uknowledge.uky.edu/entomology_etds/16.
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Aircraft strikes are a significant safety hazard on airports worldwide. Wildlife management at airfields is the most effective tactic to reduce airstrike risk – to modify the habitat to be undesirable to animals. Tall fescue grasses containing a fungal symbiont may serve that purpose. They produce alkaloids that convey resistance to some grass-feeding invertebrates, which might in turn reduce incidence of insectivorous birds. A commercial endophytic grass (Avanex™) consisting of ‘Jackal’ tall fescue infected with a unique endophyte (AR 601) is purported to contain especially high levels of alkaloids and to reduce bird populations if planted at airports. I evaluated it against the common KY31 tall fescue with its wild-type endophyte for invertebrate and vertebrate deterrence. Invertebrate abundance, survival, growth, and development were generally similar on Jackal E+ or KY31 E+. Spanish goats and wild birds showed no avoidance of Jackal E+, nor did Jackal E+ contain significantly higher levels of alkaloids than did KY31 E+. The Avanex™ tall fescue was not any better than KY31 in deterring herbivores but the concept is sound. However, better understanding of the relationship between grass, endophyte, alkaloid, and herbivore is needed to inform how such grasses might be used to reduce bird strike hazard.
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Wildsmith, Michelle Deanne. "Relationships between benthic macroinvertebrate assemblages and habitat types in nearshore marine and estuarine waters along the lower west coast of Australia /." Access via Murdoch University Digital Theses Project, 2007. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20081029.93910.
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Pardalis, George. "A comparison of the responses of benthic invertebrate individuals, populations, and communities to creosote contamination, with emphasis on Chironomidae (Diptera)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ30981.pdf.
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Layton, Raymond Jay. "Production of benthic macroinvertebrates in a river used for commercial navigation : Kanawha River, West Virginia /." Thesis, This resource online, 1985. http://scholar.lib.vt.edu/theses/available/etd-03032009-041041/.
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Kintner, Anna Helen. "Hydrozoan jellyfish and their interactions with Scottish salmon aquaculture." Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/16939.
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Medusozoan jellyfish (Classes Scyphozoa and Hydrozoa) have gained a degree of worldwide notoriety in the last fifteen years, particularly as anthropogenic influences such as climate change and overfishing push some ecosystems toward their advantage (Lynam et al. 2005, Purcell and Arai 2001, Purcell et al. 2007, Purcell 2012, Flynn et al. 2012, Dawson et al. 2014). Accordingly, both the lay and scientific media have paid a good deal of attention to jellyfish bloom phenomena and their impacts on human activities, but the bulk of this attention has been devoted to larger, visually obvious species of Class Scyphozoa. Only recently have their smaller cousins, the hydrozoans, come to be recognized as potentially problematic. This thesis examines population ecology of hydrozoan medusae (hydromedusae) and their implications for salmon aquaculture in Scotland. My review of available literature has found hydrozoans to be a recognized - though under- studied - problem for Scottish salmon (Chapter 1, Prospective monitoring of hydromedusa populations at salmon aquaculture facilities). Typically, hydrozoan populations at salmon farms have been discussed in the scientific literature only in the context of extremely dense visible blooms or in the wake of major mortality incidents. This retrospective, rather than prospective, approach has left a dearth of knowledge pertaining to hydromedusan interactions with farmed fish, with both fish welfare and industry economics vulnerable to future blooms. This thesis sought to build a basis for the goals of prediction, avoidance, and mitigation of harmful hydrozoan jellyfish blooms. First and foremost, this required the development of a prospective time-series dataset of hydromedusan occurrences at salmon farms (Chapter 2, Bacterial genera biodiversity in three medusozoan species in Shetland). To this end, four farms were recruited as participants across a three-year survey. Weekly plankton tow-based sampling at these sites identified which hydrozoan species could be expected to produce blooms, the seasonality of such blooms, and the pathological sequelae that could be expected in salmon after exposure to such blooms. Following one particularly dramatic bloom, a spike in gill pathologies in salmon was observed, followed by a spike in overall mortality and the eventual loss of up to £2.5 million value as the fish were humanely culled. This survey also demonstrated that hydromedusan blooms are usually spatially and temporally patchy, limiting the opportunities for geographically-encompassing predictive power. Instead, individual aquaculture facilities may require site-specific risk assessment and planning frameworks to monitor and cope with blooms. Potential methods for continued basic monitoring and a mitigation strategy based on minimizing contact between fish and high-density blooms are suggested. A second mitigation goal examined the theory that medusae may act as vectors for microbial pathogens, particularly Tenacibaculum maritimum (Ferguson et al. 2010, Delannoy et al. 2011; Chapter 3). Sampling methods designed to target T. maritimum were employed with the aim of determining its distribution and role as a symbiont in various life stages of medusozoan species. While T. maritimum itself was not observed, a number of other fish pathogens were found in close association with several species. This included Aeromonas salmonicida, known to cause furunculosis in aquaculture of both salmon and trout (Nomura et al. 1992). Further work is required to piece together the nature of these associations. Finally, Chapter 2 identified a particular hydrozoan genus, Obelia, as a likely significant contributor to blooms at salmon aquaculture sites. One of its species, O. geniculata, has a widely distributed and well-recognized benthic colonial life stage (called the hydroid stage) in Scottish nearshore sublittoral environments. In attempting to sample these hydroids from previously well-colonized sites in Shetland in late 2012, it became apparent that a severe local reduction in the benthic population was taking place. This allowed for the opportunity to study phylogeographic population structure - i.e. the boundaries of its gene pool(s) in Scottish waters and its potential for dispersal during one seasonal reproductive period - using a molecular study of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene (Chapter 4, Phylogeographic analysis of Obelia geniculata populations in the north of Scotland). In sampling immediately after the observed dieback, O. geniculata was found to follow a south-to-north pattern of genetic grouping, as well as a confirmed dieback. However, this pattern disappeared in samples collected after the population had recovered, probably due to the immigration of genetically novel individuals. This finding, in conjunction with the spatial-temporal patchiness found in the medusa bloom stage, suggests the importance of the larval stage as the primary stage for dispersal in the plankton. This study was also able to compare present population genetic data with a set of O. geniculata mtCOI data collected between 1998 and 2002. The combined data potentially show a high degree of mixing across a number of North Atlantic regions, including Icelandic and North American sites. Further investigation will be required to discern whether this pattern is temporally based (i.e. artefact of 15 years' elapsed time in opportunities for population mixing), or whether ecological, anthropogenic, or combined mechanisms are facilitating rapid transport of propagules to yield a well-mixed population. Further work in refining prediction and mitigation is still needed, as are effective veterinary interventions in the event of blooms. Continued study into the ecological patterns of colonization and dispersal may help to minimize exposure to blooms, by helping to assess site-based risks. This research forms the basis for such studies into hydrozoan interactions with salmon farms in Scotland, and how the industry might seek to minimize their impacts.
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Wilson, Sarah Jane. "Freshwater macroinvertebrate communities on exotic and native plants." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101665.
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Aquatic plants play an important role in the survival and proliferation of invertebrates in freshwater ecosystems. Exotic plants are now common in North American lakes and rivers, where they may displace native plants, thereby potentially altering epiphytic invertebrate communities. Differences in aquatic invertebrate communities on native and exotic plants are examined here through (1) a meta-analysis of published data, and (2) two field surveys in northeastern North America that compared invertebrates on the exotic Myriophyllum spicatum and Potamogeton crispus to those on their native congeners. The meta-analysis revealed that exotic plants generally support lower invertebrate abundance than do natives, while invertebrate taxa richness tends to be similar on exotic and native plants. The field surveys demonstrated that M. spicatum and P. crispus support significantly different invertebrate densities and lower taxa richness than their structurally similar native congeners. These results suggest that the replacement of native plants by exotics---even those with similar morphology---may cause concomitant changes to aquatic ecosystems.
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Sutcliffe, Karen. "The conservation status of aquatic insects in South-Western Australia /." Access via Murdoch University Digital Theses Project, 2003. http://wwwlib.murdoch.edu.au/adt/browse/view/adt-MU20040430.153605.
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Conrad, Richard C. "Comparison of macroinvertebrate assemblages in a first- and second-order stream in Wilber Wright State Fish and Wildlife Area, Henry County, Indiana in 2000." Virtual Press, 2003. http://liblink.bsu.edu/uhtbin/catkey/1273262.
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Macroinvertebrate assemblages were semi-quantitatively sampled from the Little Blue River and an isolated headwater stream in Wilbur Wright Fish and Wildlife Area from March through November of 2000. Physicochemical conditions and qualitative habitat characteristics were recorded at each site. Each stream contained unique community assemblages based on taxa richness, composition, functional feeding groups, behavioral groups, reproductive habits, and drought tolerance/avoidance. Collections from the first-order stream contained fewer taxa and a greater proportion of non-insects and tolerant taxa than those from the Little Blue River. Taxa from the Little Blue River were adapted for filtering/collecting and for swimming or clinging, while taxa from the first-order stream were primarily gathering/collecting and swimming or sprawling. The proportion of taxa with adaptations for drought resistance or avoidance was significantly higher in the first-order stream than in the Little Blue River (p<0.001).Department of Biology
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Miller, Anna Aroha, and n/a. "Enemy escapee or trojan horse? : investigation of the parasite burdens of native and introduced marine crabs and bivalves in New Zealand." University of Otago. Department of Zoology, 2007. http://adt.otago.ac.nz./public/adt-NZDU20080131.092837.
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The Enemy Release Hypothesis proposes that introduced species often achieve larger individual sizes and greater population abundance in their introduced range because they have escaped their natural enemies - predators and parasites - that regulate populations in their native range. The main objective of this study is to test the Enemy Release Hypothesis (ERH) by investigating the identity, prevalence and intensity of parasites in two marine species introduced to New Zealand - the recently introduced but spatially restricted Asian portunid crab, Charybdis japonica, and the longer-established Asian nesting mussel, Musculista senhousia. Host choice of a native generalist parasite presented with the non-native and native mussels, and prey selection by a native predator presented with these bivalves will be examined. This is the first study of its kind in New Zealand.
The parasite fauna of the only established New Zealand population of C. japonica (Waitemata Harbour, Auckland), was compared to that from (a) a population of C. japonica from its native region (Japan) and (b) to multiple populations of the native New Zealand crab Ovalipes catharus, a native New Zealand portunid. Results showed the introduced crab harboured only one species of endoparasite (a nematode), and two types of melanised lesions. Neither the parasite nor the lesions were present in the native crab populations. The native crab was host to only one parasite species, which occurred at very low prevalence, and was present in only one of the six populations examined from throughout New Zealand. Carapace width in the introduced crab was no larger than that reported in literature from its native are, but was larger than carapace widths of the Japanese sample.
M. senhousia was examined from five sites within New Zealand. Parasites in M. senhousia were compared with a sympatric native bivalve, Austrovenus stutchburyi, two native mytilids, (Perna canaliculus and Xenostrobus pulex) and with samples of M. senhousia from Italy and the USA where it is introduced, and Japan where it is native. Two native generalist parasites, the pea crab Pinnotheres novaezelandiae, and a copepod, were found within M. senhousia in New Zealand, but only at low prevalence. A greater array of organisms was associated with the native bivalves. No parasites were recovered from any of the overseas samples of M. senhousia, including the Japanese samples. This may be caused by the preservation medium used, but could be a true reflection of the parasite fauna in these populations.
The site where the two native parasites were exploiting M. senhousia was the only site sampled where two native mussels, P. canaliculus and X. pulex, also occurred. Consequently, effects of these two generalist parasites on the three mussel species were examined. In P. canaliculus, presence of native pea crabs was associated with lower tissue dry weight and greater shell depth. Shell width and depth were both greater in the presence of copepods. However, the prevalence of pea crabs and copepods was much lower in M. senhousia compared to the two native mussels, indicating some release from the effects of these parasites for the non-native species. Experimental choice tests showed that the pea crab, P. novaezelandiae, does not actively select M. senhousia as a host, preferring the larger native mussel, P. canaliculus. Rates of infection of M. senhousia are, therefore, likely to remain low in natural habitats where there are large numbers of native hosts. In addition, a generalist predator, the crab O. catharus, showed no preference when foraging on the three mussel species under experimental conditions. Thus, some predation pressure may be exerted on M. senhousia by this native crab in the natural environment.
Investigation of multiple populations of both native and non-native species has shown large variation in parasite prevalence and intensity among populations of each species. After examining C. japonica and the comparable native O. catharus, evidence to support the ERH was found to be weak. As the native crab was relatively free of parasites, it seems unlikely that parasite infection is important within native populations and therefore, the success of C. japonica is unlikely to be caused by comparatively greater freedom from parasites (a central tenet of the ERH). There was also no evidence for host-switching by native parasites into the introduced C. japonica population. In contrast, native parasites were present at very low prevalence in the non-native mussel M. senhousia. Length of time since introduction can be an important factor in host switching between native and introduced hosts, but unless prevalence of these parasites is high, the introduced species still escapes from enemies that could control a population. Therefore every non-native species needs to be examined using multiple populations to investigate variation in parasite fauna, prevalence and intensity, as the same species, if introduced numerous times, could potentially show contrasting results for the ERH unless multiple populations are examined.
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Narog, Marcia Gay. "Invertebrate responses to the effects of thinning and understory burning in a canyon live oak (Quercus Chrysolepis) forest in the San Bernardino Mountains, California." CSUSB ScholarWorks, 1991. https://scholarworks.lib.csusb.edu/etd-project/750.
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Sherman, Craig D. H. "The importance of fine-scale environmental heterogeneity in determing levels of genotypic diversity and local adaptation." Access electronically, 2006. http://www.library.uow.edu.au/adt-NWU/public/adt-NWU20060726.114643/index.html.
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Keleher, Mary Jane. "Bioassessment and the Partitioning of Community Composition and Diversity Across Spatial Scales in Wetlands of the Bonneville Basin." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1986.pdf.
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Owen, Jenny. "Provision of habitat for black grouse Tetrao tetrix in commercial forest restocks in relation to their management." Thesis, University of Stirling, 2011. http://hdl.handle.net/1893/3444.
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As planted forests mature and are clearfelled in patches, second rotation tree crops (restocks) become available to black grouse, a species of conservation concern in the UK. Currently, only a limited amount is known about the resources provided by this habitat to black grouse and their broods. The aims of this study therefore, were to investigate the recovery of field-layer vegetation and the invertebrate population from restock through to canopy closure of planted trees, assess the duration of habitat availability and food resources to black grouse, and understand how forest management could improve provision. Changes to the abundance of predators resulting from habitat management were also considered. The comparative habitat quality of restocks was assessed in a wider landscape context. Field-layer vegetation in 72 restocks in two afforested areas in the north-east and the south-west of the Scottish Highlands was surveyed. On average, only 60% of ground in restocks was re-planted with second rotation trees, with the remainder left unplanted. Initial vegetation recovery was generally impeded by timber harvest residues (mainly brash), which comprised up to 50% of total ground cover two years after restock. Increased cover of heather Calluna vulgaris, often an important component of black grouse habitat, and decreased brash cover were recorded in areas of restocks where first-rotation timber was removed by cable-winch (compared with harvester and forwarder removal) and in planted areas (compared with areas left unplanted). Bilberry Vaccinium myrtillus and cotton grass Eriophorum spp. occurrence was recorded infrequently irrespective of restock age or management. Heather generally dominated the field-layer six years after restock, reaching a height and density reported to be suitable for black grouse nesting and brood cover in other studies. The onset of tree canopy closure as early as eight years suggests that suitable black grouse habitat availability in restocks is likely to be severely limited in duration. Brash removal, or break-up and re-distribution of the brash layer, positively affected the recovery of field-layer vegetation species potentially of use to black grouse. Extending the fallow period prior to restock resulted in an extended period of suitable habitat available to black grouse prior to canopy closure. However, habitat created by extending the fallow period also attracted a higher number of mammalian predators of black grouse. In the longer term, areas of restocks left unplanted should provide a valuable open-ground resource after canopy closure of the planted crop, although results suggest that management to prevent encroachment of naturally regenerating non-native trees is likely to be necessary. Invertebrate taxa selected by chicks in previous black grouse studies were available in all ages of restock studied. Taxa abundance differed as restocks aged and field-layer vegetation developed, although contrasting habitat preferences of taxa meant that each was affected differently by restock management. No single forest management method positively increased abundance of all taxa. Abundance of Lepidoptera larvae, a key food item for black grouse chicks, was positively related to dwarf shrub cover. An extended fallow period prior to restock should prolong increased larvae availability to chicks. Provision of preferred field-layer vegetation habitat and invertebrate abundance in restocks was comparable to habitat surrounding leks - areas likely to be occupied and utilised by black grouse. Restocks had a comparatively low occurrence of key plant species, including bilberry Vaccinium myrtillus and cotton grass Eriophorum spp. Cover of the dwarf shrub bog myrtle Myrica gale, positively associated with Lepidoptera larvae abundance in habitat surrounding leks, was absent from restocks. The abundance of other invertebrate taxa considered was similar between leks and restocks. Study findings are discussed with reference to black grouse conservation and commercial forestry systems in Europe. Management recommendations to improve habitat for black grouse in second rotation planted forests in Britain are provided.
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Babin, Régis. "Contribution à l'amélioration de la lutte contre le miride du cacaoyer Sahlbergella singularis Hagl. (Hemiptera : Miridae). Influence des facteurs agro-écologiques sur la dynamique des populations du ravageur." Phd thesis, Université Paul Valéry - Montpellier III, 2009. http://tel.archives-ouvertes.fr/tel-00871800.
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L'objectif de ce travail est d'améliorer notre compréhension des mécanismes et d'évaluer les facteurs agro-écologiques impliqués dans la dynamique spatio-temporelle des populations naturelles de Sahlbergella singularis. Le calcul des tables de vie sur une population d'élevage a révélé que S. singularis est une espèce à croissance lente. Ceci expliquerait le fait que le ravageur est généralement présent à de faibles densités dans les plantations. L'étude des paramètres démographiques de la population d'élevage a montré que la fécondité est un paramètre-clé des fluctuations saisonnières des populations naturelles. Leur croissance serait liée à la présence de jeunes cabosses sur les cacaoyers fournissant aux femelles une ressource alimentaire favorable à la reproduction. L'étude de l'influence des facteurs agro-écologiques sur les densités de populations de S. singularis en plantation a révélé que les densités dépendent des conditions parcellaires de culture du cacaoyer. Parmi les pratiques culturales, les traitements insecticides, l'ombrage et le recours aux variétés hybrides sont des facteurs déterminants. En outre, les populations du ravageur sont fortement agrégées dans les zones des plantations bénéficiant d'un ensoleillement maximal. Enfin, l'ombrage fourni par les arbres forestiers s'est avéré plus homogène que l'ombrage d'arbres fruitiers et par conséquent moins propice au développement des poches à mirides. Les recommandations de lutte préconisées par la recherche agronomique sont rarement appliquées par les planteurs. Aussi, nos résultats ont-ils été discutés dans l'optique d'adapter ces recommandations au contexte de culture du cacaoyer qui prévaut actuellement au Cameroun
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Macdonald, Hannah. "Population genetics and demographic resilience in three aquatic invertebrates." Thesis, Cardiff University, 2016. http://orca.cf.ac.uk/100387/.
Full textAbstract:
Freshwater environments are threatened worldwide by external stressors and biodiversity decline, with major implications for ecosystem resilience. The genetic consequences so far have been neglected, especially for freshwater invertebrates, though their abundance, diversity, ease of sampling and functional importance renders them ideal candidates for genetic appraisal. For three freshwater invertebrates (Amphinemura sulcicollis, Isoperla grammatica and Baetis rhodani) novel microsatellite markers were developed so that genetic structure, and genetic diversity could be assessed throughout upland Wales. The aim was to investigate dispersal and the genetic response to environmental stressors. Genetic diversity in these species was compared to species diversity across whole macroinvertebrate assemblages to investigate what factors might cause a correlation between these fundamental levels of biodiversity. The demographic history of each species was also investigated with the aim of assessing whether reduced genetic diversity was due to bottlenecks and more broadly, what this indicates in terms of the populations’ resilience. Species differed in their genetic structure and genetic diversity. All three species showed effective dispersal and geneflow, with each species displaying panmixa across catchments in southern and mid-Wales. However, A. sulcicollis and I. grammatica revealed genetic isolation and reduced genetic diversity at specific northern sites. Genetic and species diversity were correlated positively only in A. sulcicollis, where isolation combined with a common driver were the likely cause. There was evidence of recent bottlenecks in all three species. All these results could be explained by an underlying genetic response to post-industrial acidification: reduced genetic diversity correlated significantly with acidity for A. sulcicollis, while reduced species diversity and genetic bottleneck signatures was consistent with chronic and episodic acidification across the Welsh region. Overall, these results show how a positive correlation between species and genetic diversity can never be assumed, and illustrate how assessments of genetic health expand insights available from traditional biodiversity assessment.
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Tokeshi, M. "The population and community ecology of chironomids in a small temperate stream." Thesis, University of East Anglia, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.355362.
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Tassinari, Stefano. "Genetic structure and connectivity between populations of two common Mediterranean sessile invertebrates." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4573/.
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Population genetic and phylogeography of two common mediterranean species were studied in 10 localities located on the coasts of Toscana, Puglia and Calabria. The aim of
the study was to verify the extent of genetic breaks, in areas recognized as boundaries between Mediterranean biogeographic sectors. From about 100 sequences obtained from the mitochondrial Cytochrome Oxidase subunit I (COI) gene of Halocynthia papillosa and Hexaplex trunculus genetic diversity, genetic structure at small and large distances and demographic history of both specieswere analyzed. No evidences of genetic breaks were found for the two species in Toscana and Puglia. The genetic structure of H. trunculus evidences the extent of a barrier to gene flow localized in Calabria, which could be represented by the Siculo-Tunisian Strait and the Strait of Messina. The observed patterns showed similar level of gene flow at small distances in both species, although the two species have different larval ecology. These results suggest that other factors, such as currents, local dynamics and seasonal temperatures, influence the connectivity along the
Italian peninsula. The geographic distribution of the haplotypes shows that H. papillosacould represent a single genetic pool in expansion, whereas H. trunculus has two
distinct genetic pools in expansion. The demographic pattern of the two species suggests that Pleistocene sea level oscillations, in particular of the LGM, may have played a key role in shaping genetic structure of the two species. This knowledge provides basic information,
useful for the definition of management plans, or for the design of a network of marine protected areas along the Italian peninsula.
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Batley, Jacqueline. "A study of the population ecology of willow beetles (Phyllodecta spp.) using microsatellites." Thesis, University of Bristol, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343295.
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St, Clair James J. H. "Plovers, invertebrates and invasive predators : aspects of the ecology of some island populations." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.537714.
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This thesis makes progress in two broad fields of research, descriptive ornithology and invasion ecology, based largely on fieldwork in the Falkland Islands. Populations of two little-studied South American waders, the Two-banded Plover Charadrius falklandicus and the Rufous-chested Dotterel Charadrius modestus, were monitored over a four-year period at a single island site: in chapters two, three and four this thesis presents information on the diel pattern ofincubation sharing by males and females of both species (the two species showed opposite diel sex-roles), data on morphology including sexual dimorphism (male-biased in both species), breeding systems data including estimates of mate fidelity, and for Two-banded Plovers, demographic estimates including annual survival rates of adults and hatching success of nests. These are among the first detailed studies of the breeding behaviour and life-histories of anysouthern South American waders. Concurrent with the single-site wader study, an inter-islandnatural experimental approach was used to investigate the effects of non-native mammalian predators, firstly on the expression of anti-predator behaviour in the Two-banded Plover (chapter five) and secondly on the relative abundance of populations of an endemic insect, the Falkland Camel Cricket Parudenus falklandicus (chapter six). The latter chapters both infer strong effects of non-native mammalian predators: firstly, Two-banded Plovers expressed much larger flushing distances in response to an approaching (human) stimulus at sites where feral cats Felis catus were present, although flushing distances were shorter when background exposure to humans was relatively high (I interpret these effects as generalisation and habituation respectively). Secondly, the relative abundance of Camel Crickets in a given habitat type was substantially higher in the absence of Norway Rats Rattus norvegicus, regardless of whether the rats were naturally absent orhad been deliberately eradicated. Following the apparently strong effect of rats on insects in the Falkland Islands, in chapter seven I use literature from other island groups to review the effects of invasive rodents on island invertebrate populations; I conclude that negative effects are widespread and non-randomly distributed among invertebrate species, with large invertebrates particularly susceptible to rodent impacts. Finally, in chapter eight, potentially productive areas for future research and synthesis are suggested.
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Harwood, Robert William John. "The management of arable field margins to enhance natural populations of beneficial arthropods." Thesis, University of Southampton, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307086.
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Green, J. "Environmental and genetic influences on dauer larvae development in growing populations of Caenorhabditis species." Thesis, Canterbury Christ Church University, 2014. http://create.canterbury.ac.uk/14316/.
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Phenotypic variation manifests from either simple (monogenic) or complex (multigenic) traits. Variation due to genetic and environmental influences is important because the ability to produce a range of phenotypes is essential for adaptive evolution. Complex traits are important not only for evolution, but because many diseases are complex traits. The genetic architecture of complex traits can be very multifaceted, with a large number of causal genes each having a small effect on the overall heritability of the trait, and as such our understanding of the genetic architecture and control of complex traits is limited. Complex traits are studied through quantitative trait loci mapping and genome-wide association studies. Since there are a great range of resources available for the nematode Caenorhabditis elegans, this is an appropriate system in which to study the genetic architecture of complex traits. Dauer larvae development represents a suitable complex trait as many of the genes involved and their genetic pathways have been identified. This trait is also important for the clear links between the dauer larvae of free-living species and the infective stages of many parasitic nematodes, and is therefore important as a model complex trait. Dauer larvae are routinely studied under unnatural conditions, with a cohort of aged-matched worms exposed to concentrated pheromone from many worms, conditions that are not obviously ecologically or evolutionally relevant. It is therefore important to understand the dynamics of growing populations in the laboratory both specifically to understand C. elegans, and generally to understand the genetics of complex traits. Methods have been established for the analysis of population growth assays, and experiments to validate this style of assay have been carried out for the analysis of dauer larvae development in a growing population. In this, extensive variation in dauer larvae development between natural wild isolates and the canonical isolate N2 has been shown, variation which has previously not been demonstrated in standard dauer larvae assays. The genetic basis of this variation was also investigated using two Recombinant Inbred Line (RILs) panels made from two distinct parental genotypes of C. elegans, Isogenic Lines (ILs) of C. elegans and also a C. briggsae RIL panel. These analyses revealed that the genetic architecture of dauer larvae development in growing populations is highly complex, with a large number of QTLs affecting this trait. Also, comparison of the results from the different mapping approaches (RILs vs. ILs) revealed variation in their power to detect QTLs, as the ILs were capable of identifying far more QTLs than the RILs. Three candidate genes which have an effect on dauer larvae development in growing populations were identified and analysed. These candidates are npr-1, srg-36 and srg-37, each showing a negative effect on dauer larvae development in a growing population and an allelic effect of variation at npr-1. Together, these results demonstrate that extensive variation in dauer larvae development can be analysed in growing populations, that the underlying genetics can be mapped and that candidate genes can be identified for the underlying regions.
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Leiva, Martinez Carlos. "Population genomics, phylogeographic history, and evolutionary patterns in Antartic shallow-water benthic invertebrates." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/668297.
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Benthic organisms inhabiting the shallow waters of the Southern Ocean are considered excellent models to study evolutionary processes, population connectivity patterns, and adaptation. They have evolved in an extreme environment, with expanding and retreating periods following glacial cycles, in an alternation pattern. Repeated rounds of population fragmentation in glacial refugia during glacial cycles followed by expansions and secondary contacts during interglacials were the main evolutionary force that brought Antarctic shallow-water ecosystems to their current state. In my PhD dissertation I have investigated in detail these singular evolutionary histories left in the genomes of our target species. Besides the past geological events, currently, threats from global warming arrive to the isolated southernmost continent. Indeed, coastal waters off West Antarctica are some of the most affected oceanic regions of the planet by global warming, with rather pessimistic projections for the near future. Considering this and the increasing local threats to which shallow-water ecosystems are exposed, it is fundamental to develop a well-connected network of Marine Protected Areas (MPAs) throughout the Southern Ocean. Despite genetic connectivity is not usually considered in MPA planning, population genetic studies can provide extremely valuable information to design connected MPA networks. In my dissertation I have also disentangled gene-flow patterns of Antarctic shallow-water benthic invertebrates, aiming to help to improve the current status of Southern Ocean MPAs.
In order to achieve my goals, I combined information coming from ‘traditional’ genetic markers, single nucleotide polymorphisms (SNPs) derived from restriction-site associated DNA sequencing (ddRADseq), transcriptomes, and draft-level genomes. A wide range of species presenting different reproductive modes was selected in order to test whether this factor plays a role on connectivity and evolutionary patterns in the explained scenario of glacial alternations: the brooding congeneric nemerteans Antarctonemertes valida, A. riesgoae, and A. unilineata; the demosponges Dendrilla antarctica and Mycale acerata, which present lecithotrophic larvae; and the annelids Pterocirrus giribeti (new species described in the Chapter 1 of my PhD dissertation) and Neanthes kerguelensis, that presumably presents planktotrophic larvae.
Our results regarding the evolutionary history of our target species revealed different glacial-refugium strategies independent of their reproductive mode, and generalised signals of bottleneck events. Moreover, blurred species boundaries were detected for the Antarctonemertes lineages, with a central role of glacial cycles in their introgressive evolutionary history. Additionally, we identified adaptive genes for particular glacial-refugium strategies and for the rise of prezygotic barriers during speciation and reinforcement events. Our connectivity results confirmed that genetic connectivity in the Southern Ocean is not determined by a priori dispersal abilities resulting from different reproductive strategies. We revealed an overall high gene flow along the Western Antarctic Peninsula (WAP), which is particularly exceptional for sponges and brooding species. Interestingly, loci under divergent selection were identified for D. antarctica despite admixture, broadly differentiating between the populations of Northern and Southern WAP. We suggest that ongoing natural selection is governed by differences in sea-ice extent and duration, exhibiting the vulnerability of the WAP benthic ecosystems due to the decline in the sea ice predicted for the near future. Finally, we demonstrated that long-distance connectivity did not surpass the regional WAP scale, supporting the implementation of an MPA covering the WAP and the coastal waters off the South Orkneys.
Overall, the studies presented in my PhD dissertation represent a step forward in understanding global forces and processes affecting the evolutionary history of Antarctic marine organisms. We illustrated the adaptability of shallow-water benthic invertebrates to the natural changes of the Southern Ocean, while manifesting their vulnerability to future global warming. Remarkably, we highlight the importance of using population genetic data of various benthic invertebrate species to implement MPA networks in one of the most threatened areas of the planet by global warming. The results of my thesis will be fundamental to address the suitability and effectiveness of an MPA network comprising the already implemented MPA at South Georgia and South Sandwich Islands and the proposed MPA covering the WAP and the South Orkney Islands, essential for the survival of Antarctic marine ecosystems.
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Fontanilla, Ian Kendrich C. "Achatina (Lissachatina) fulica Bowdich : its molecular phylogeny, genetic variation in global populations, and its possible role in the spread of the rat lungworm Angiostrongylus cantonensis (CHEN)." Thesis, University of Nottingham, 2010. http://eprints.nottingham.ac.uk/11069/.
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The Giant African Snail, Achatina (Lissachatina) fulica Bowdich, is a tropical crop pest species with a widespread distribution across East Africa, the Indian subcontinent, Southeast Asia, the Pacific and the Caribbean. It is also a known intermediate host of the rat lungworm, Angiostrongylus cantonensis, which can infect humans and cause eosinophilic meningitis. The phylogenetic position of A. fulica within the Achatinoidea and the Achatinidae was investigated using segments of the nuclear ribosomal (r) RNA cluster, actin and histone 3 genes and the mitochondrial CO1 and 16S rRNA genes. Results from molecular data support the monophyly of the Achatinidae based on the taxa surveyed as well as the morphological distinction of the Eastern Achatina (Lissachatina) from the Western and Central Achatina (Achatina); Lissachatina should therefore be elevated to genus status. The results also show non-monophyly of the Coeliaxidae, Ferussaciidae and Subulinidae; the taxonomy of these families must therefore be reassessed. The extent of genetic diversity in global A. fulica populations was also determined using an SSCP molecular marker developed from the 16S rRNA gene. Results reveal only one haplotype (C) emerged from East Africa and spread globally. The rat lungworm (Angiostrongylus cantonensis) has a parallel distribution with A. fulica, and the possible role of the snail in the spread of the parasite is investigated using a molecular marker derived from the small subunit (SSU) rRNA gene. A survey of the parasite within the route of dispersal of A. fulica detected A. cantonensis only in the Philippines and the French Polynesian territory of Tahiti, the latter of which being the first reported case of A. cantonensis infection for Achatina fulica in that territory. Due to the limited sampling of the snail and the patchy distribution of the parasite, there are insufficient data at this time to assess the role of Achatina fulica in the spread of Angiostrongylus cantonensis.
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Homyack, Jesica Anne. "Effects of Forest Regeneration Methods on Salamander Populations in Central Appalachia." Diss., Virginia Tech, 2009. http://hdl.handle.net/10919/26614.
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In forested ecosystems, salamanders occupy important ecological roles as predator, prey and as potential regulators of ecological processes. The effects of forest management, particularly clearcut harvesting, on salamanders have been well documented; removal of overstory trees negatively affects abundances of salamanders. However, the length of time that salamander populations remain depressed following forest harvesting and factors limiting population recovery have been a source of controversy in the literature and are the goal of this dissertation. As part of the Southern Appalachian Silviculture and Biodiversity (SASAB) project (Chapter 1), a long-term replicated field experiment designed to evaluate a range of silvicultural treatments on biodiversity, I evaluated specific hypotheses related to salamander populations, their prey, and their habitat.
First, I examined long-term trends in salamander abundances across a range of silvicultural treatments to determine whether negative effects of forest harvesting persisted for 13-years after harvest (Chapter 2) and to document the effects of multiple harvests on salamanders (Chapter 3). The relative abundances of terrestrial salamanders were quantified in six silvicultural treatments and an unharvested control and on six replicated field sites with night-time, area-constrained searches. Across 13-years of post-harvest data, terrestrial salamander abundances generally were lower in silvicultural treatments with some disturbance to the canopy (group selection harvest through silvicultural clearcut). Further, a comparison of demography of common species of salamanders suggested that differences in habitat quality existed between harvested and unharvested experimental units (EUs). A second harvest in the shelterwood plots to remove overwood had a cumulative negative effect on salamanders at one of two sites studied. Additionally, I conducted a sensitivity and elasticity analysis for eastern red-backed salamanders (Plethodon cinereus) and modeled population growth to evaluate the contribution of demographic parameters to population recovery. These analyses indicated that adult survival was the parameter with the greatest influence on the population growth rate and that >60 years would be required for recovery of salamander populations to preharvest levels even if habitat conditions were restored to preharvest conditions immediately.
Next, I quantified the bioenergetics of salamanders across a disturbance gradient to evaluate whether changes to (1) invertebrate prey, (2) energy expenditure for basic maintenance costs, and or (3) an index to body condition could help explain observed changes to abundances or demography of salamanders from forest harvesting (Chapter 4). Although I did not detect a difference in abundances of invertebrates along the disturbance gradient, I determined that salamanders in recently disturbed forest stands expended approximately 33% more energy for basic maintenance costs in an active season and the body condition of salamanders was greater at one of two sites in disturbed EUs. Thus, the bioenergetics of terrestrial salamanders may have been affected by increasing temperatures from silvicultural disturbance and may cause salamanders to allocate less energy to reproduction or growth because of increased maintenance costs.
In collaboration with Eric Sucre, Department of Forestry at Virginia Tech, I examined the effects of salamanders on invertebrates and ecosystem processes, specifically leaf litter decomposition. We constructed 12 in situ field mesocosms and I manipulated densities of red-backed salamanders into zero, low, and high density treatments. From June 2006-June 2008, I estimated invertebrate abundances, rates of leaf litter decomposition and food habits of salamanders across treatments. I found that invertebrate abundances were more affected by season than by the density of salamanders and that rates of leaf litter decomposition did not differ among salamander treatments. Salamanders were euryphagic and consumed more (by abundance and volume) herbivorous invertebrates than predators or detritivores.
Finally, I modeled habitat relationships of terrestrial salamanders at two spatial scales on the SASAB study sites (Chapter 6). I quantified abundance of salamanders with area-constrained searches during warm rainy nights and measured forest characteristics related to foraging or refugia habitats or that described the overstory and understory of forest stands. At the scale of the 30 m2 transect and the 10 m2 sub-transect, abundance of salamanders was best described by models that incorporated descriptors of canopy cover and woody and herbaceous understory vegetation. Thus, terrestrial salamanders may have responded positively to forest stands with a mature overstory and structurally diverse understory for foraging habitat.
Collectively, these data suggest that recovery of salamander populations after forest harvesting will take approximately 60 years, and that life history characteristics (low fecundity, late sexual maturity) and possibly changes to bioenergetics may contribute to the slow recovery. Further, silvicultural practices that retain some canopy trees through a rotation may have a more rapid return of salamander populations to preharvest levels and may encourage development of understory structure for salamander foraging. Although these data fill some gaps in knowledge of relationships between silviculture and terrestrial salamanders, many questions about long-term effects of disturbances on populations and habitats remain. My modeling of recovery of salamander populations depended on estimates of a survival from a congener, and I did not document whether forest harvesting decreases survival of terrestrial salamanders. Lastly, the influence of stochastic events on population dynamics particularly in disturbed stands was not examined in this dissertation. Therefore, future research on the SASAB study sites should continue to track abundances and demography across the disturbance gradient, acquire age-specific estimates of survival, determine whether salamanders exhibit density dependence, develop estimates of entire energy budgets, and use manipulative laboratory experiments to describe the role of plethodontid salamanders in ecosystem functions.Ph. D.
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Stauffer-Olsen, Natalie Janelle. "Spatial and Temporal Variability in Benthic Invertebrate Assemblages and Population Genetics in a Lake and Stream System." Thesis, University of California, Berkeley, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10607118.
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An understanding of the spatial and temporal diversity of benthic invertebrates is necessary to understand, manage, and protect freshwater habitats. Benthic invertebrates are important components of aquatic ecosystems and are frequently used in bioassessment and biomonitoring programs. Benthic invertebrates can also play a role in nutrient cycling in lentic environments through bioturbation activities. This dissertation uses a range of techniques and analyses to understand the arrangement of benthic invertebrate diversity in Upper Klamath Lake, Oregon, and several watersheds in northern southern California.
Upper Klamath Lake (UKL) is a large, shallow, naturally eutrophic lake that has experienced declines in water quality, which has led to annual cyanobacterial blooms of Aphanizomenon flos-aquae. Benthic invertebrates can increase autochthonous nutrient cycling through benthic bioturbation activities. In order to better understand the role that benthic invertebrates play in UKL, I studied the density, taxonomic richness, and species composition of benthic invertebrate assemblages in three geographic regions (north, central, and south) and three habitats (littoral, open-water and trench) across UKL. I also characterized sediment composition and water quality at each collection site and determined which environmental variables correlated with differences in benthic invertebrate composition. This research is located in Chapters 1 and 3 of this dissertation.
Like benthic invertebrates in UKL, the mayfly Baetis tricaudatus is an abundant and ecologically important organism of freshwater ecosystems. Despite its widespread distribution, B. tricaudatus cannot be consistently and accurately identified and belongs to a species group known to have cryptic species diversity. While previous studies have examined the spatial distribution of this diversity, none have studied the temporal distribution. To better understand the temporal arrangement of diversity at the cytochrome oxidase subunit 1 (CO1) mitochondrial gene region, I collected B. tricaudatus specimens from 3 sites over 4 years and used haplotype networks to visualize diversity. Because my results were different than those from other studies on the same taxon, for my final chapter I analyzed Baetis rhodani group COI sequences from northern and southern California using Bayesian phylogenetic analyses and haplotype networks. This research contributes to our understanding of genetic diversity, which is an important component to biodiversity.
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Hunter, Rebecca L. Halanych Kenneth M. "Phylogeography and population structure of Antarctic ophiuroids effects of life history, oceanography and paleoclimatology /." Auburn, Ala, 2009. http://hdl.handle.net/10415/1754.
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Agatz, Annika. "Consequences of short-term feeding inhibition from exposure to pesticides for individuals and populations of aquatic invertebrates." Thesis, University of York, 2013. http://etheses.whiterose.ac.uk/5538/.
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Recently, several scientific committees of the European Commission have identified research needs to enhance the risk assessment of plant protection products (PPPs). This PhD explicitly focuses on contributing to the research needs of assessing effects under highly time-variable exposure, increasing the ecological realism in effect assessment approaches, considering effect assessment of combined stressors (natural and anthropogenic) and improving ecological modelling. The presented work focuses on the observation of potential impacts of PPPs (imidacloprid and carbaryl) on feeding of aquatic invertebrates (Gammarus pulex and Daphnia magna) under more environmentally-realistic exposures. Isolated feeding depression and its combination with additional stress is explored. Investigations include the determination of consequences of alterations in feeding for further behavioural traits of individuals and its transposition to the population level. An ecological model is used as a virtual laboratory to allow the interpretation of complex impacts observed which in turn helps to evaluate the model used. A key finding is that feeding assays with G. pulex are able to reveal impacts of PPPs at environmentally-relevant concentrations and that the measurement of recovery potential is important. However, the method used requires further improvement in order to extrapolate impacts to the population and ecosystem level. The possibility of short-term impacts on feeding causing severe impacts at the individual and population level is shown for D. magna. Direct extrapolation from the feeding assay with imidacloprid to other individual traits is not possible. Impacts are found to depend on food availability and the individual’s reproductive strategy, which is found to be more flexible under multiple stresses than has been reported in the literature. Further research is required in order to generalise these findings.
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Johnson, Philip C. (Philip Charles). "Impacts of the Pyrethroid Insecticide Cyfluthrin on Aquatic Invertibrate Populations in Outdoor Experimental Tanks." Thesis, University of North Texas, 1992. https://digital.library.unt.edu/ark:/67531/metadc279350/.
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The chemical fate and biological impacts of cyfluthrin in aquatic ecosystems were investigated using microcosms (1.9 m^3 concrete tanks) during 1989. Results were compared to a concurrent pesticide registration study using mesocosms (634.7 m^3 earthen ponds). Ten spray drift and five soil runoff simulations were conducted. Pesticide loadings were scaled by system volume, with the same experimental design in ponds and microcosms. Aqueous cyfluthrin concentrations and sediment residue values were generally higher in microcosms, while aqueous half-life was shorter in the smaller systems.
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Johnson, Collin Hauer. "Self-fertilization, Larval Dispersal, and Population Structure in the Marine Bryozoan Bugula stolonifera." Thesis, Harvard University, 2012. http://dissertations.umi.com/gsas.harvard:10180.
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Although the process by which fertilization occurs in bryozoans is well described, the ability to self-fertilize and the subsequent ecological consequences are poorly understood. Culturing experiments were conducted examining the effects of selfing on offspring survival and reproduction in the simultaneous hermaphrodite Bugula stolonifera collected from Eel Pond, Woods Hole, MA. Results from these experiments document significant decreases in survival and fecundity of selfed offspring, compared to outcrossed controls, suggesting that these animals are not routinely self-fertilizing in Eel Pond. How these arborescent colonies minimize selfing remains unclear, but it is hypothesized that conspecific aggregations could serve to minimize the chances that a colony utilizes its own sperm for fertilization. The genetic composition of these aggregations was investigated using a newly developed microsatellite library. As larvae routinely metamorphose on conspecific colonies, the possibility that larvae select or avoid their maternal colony was also investigated. Analyses of genetic structure document homogeneity throughout these aggregations on extremely small spatial scales, suggesting high amounts of larval dispersal within aggregations. When combined with results from parentage-exclusion and kinship analyses, these results indicate that a colony's nearest neighbors are not composed of siblings, potentially minimizing inbreeding. Molecular analyses were then used to determine if the high larval dispersal within aggregations resulted in high mixing between aggregations. Sites within Eel Pond separated by 100-300 m were routinely sampled from 2009 to 2011, and analyses were conducted to investigate potential inter- and intra-annual genotypic differentiation within and between aggregations. Results document that although low levels of mixing could result in increased homogeneity between some aggregations, barriers to genetic exchange prevent mixing between most sites. Further, inter-annual comparisons within sites document that significant differentiation can occur between reproductive seasons. Hence, any potential homogeneity achieved between sites during one reproductive season will likely be lost by the beginning of the next reproductive season. Additionally, while sampling in Eel Pond in 2010, I document the first occurrence from the western Atlantic Ocean of another aggregating arborescent bryozoan, Tricellaria inopinata. The growth and reproductive biology of these animals was monitored throughout 2011; results suggest that this introduction is likely to persist.
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Gardeström, Johanna. "Coping with environmental stress : from the individual and population perspective." Doctoral thesis, Stockholm University, Department of Systems Ecology, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-7311.
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Natural stress and disturbances are important factors affecting the structure and function of ecosystems. However the magnitude of stress has escalated due to anthropogenic activities. Environmental monitoring and toxicity assessments try to protect ecosystems from unwanted human alterations. The aim of this Doctoral thesis was to increase the understanding of the complex effects that environmental stress has on individuals and invertebrate populations. The low saline environment in the Baltic Sea is perceived as stressful for most organisms living there. In Paper I, it was found that Baltic blue mussels living in the less saline northern Baltic Proper (~5 psu) had lower basal metabolism and were more susceptible to toxic exposure than the mussels in the south (~7 psu). There was no genetic differentiation between the mussels from the northern and southern areas while there were genetic differences between mussels from sites within the respective areas (Paper III), indicating that there is not a simple relationship between the health of the mussels and genetic diversity in the microsatellite loci studied. In Paper IV it was found that the heat tolerance of the intertidal dogwhelk Nucella lapillus is oxygen dependent. Increased oxygen levels resulted in higher survival rate. Protein expression profiles also became more similar to those of the controls, compared to the whelks exposed to high temperature and normal oxygen levels. In Paper V and VI it was found that exposure to a single toxicant for more than one generation decreased the genetic diversity in exposed copepod populations even though abundances remained unaltered. In Paper VI, exposure to naturally contaminated sediments, which contained of a mixture of toxicants, did not decrease genetic diversity. However the genetic divergence (FST) within the treatments was very high, probably due to small effective population sizes in the replicates. Likewise in Paper III, the very low blue mussel abundance in the north together with the stressful environment suggests a small effective population in the northern Baltic Proper. In conclusion, my studies show that, measuring effects on several levels, including both functional and structural endpoints will both increase the sensitivity of the tests and increase their ecological relevance.
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Muller, Cornelius Marthinus. "The phylogeographic population structure of the Cape sea urchin, Parechinus angulosus." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/6899.
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Thesis (MSc)--Stellenbosch University, 2011.ENGLISH ABSTRACT: South Africa's coastline is in the region of 3650kms and encompasses many different and dynamic marine environments. To enhance our current understanding of the population structure and gene flow patterns of intertidal zone marine species in this region, this study sets out to investigate the phylogeographic population structure of the Cape sea urchin, Parechinus angulosus, using mitochondrial and nuclear DNA sequence data collected in 2007 and 2008. Individuals were sampled from 18 geographic locations between southern Namibia and Durban, covering nearly the full extent of the species range. Sequence data were obtained from a 790bp region of the COI mtDNA gene (n=510) and a 182bp region of the nDNA SpREJ9 gene (n=145), respectively. The mtDNA data revealed 283 polymorphic sites (36%) defining 195 haplotypes, of which 160 were unique and 35 shared among individuals. Haplotype diversity (h) was found to be high both overall (h=0.95) and for individual localities (h=0.75-0.98), with nucleotide diversity (π) being low overall (π=0.013) as well as for individual localities (π=0.0033-0.0254). AMOVA revealed significant population structure among sampling sites in the Namaqua Province biogeographical region, as well as between three of the four respective coastal biogeographic provinces/regions. Gene flow was bi-directional among sampling sites in the south coast Agulhas and East Coast Province biogeographical regions, while gene flow in the Namaqua Province appears to be dominated by northwards movement. BAPS identified a significant break in the Cape Point region, which was also reflected in the gene flow patterns and parsimony networks. This broadly corresponds to previously identified biogeographic regions as well as genetic breaks for other marine species found along this coast. Fu's Fs statistics showed strong signal(s) of population expansion for individual sampling localities as well as for the data set as a whole, while MDIV estimated a time since expansion ranging from 7733-4759 years ago. The nDNA data revealed 54 variable sites (29.7%), defining 72 alleles of which 50 were unique and 22 shared among individuals. Many of the alleles (69.4%) were restricted to single sampling sites, with Betty's Bay on the south coast being the most diverse from a genetic viewpoint. Allelic diversity was high overall (h=0.86) while nucleotide diversity was low (π=0.025). No nuclear sub-group structure was identified by BAPS, although the parsimony network revealed shallow genetic structure between the Namaqua and Agulhas Provinces, with significant pairwise ФST values also recovered between their individual coastal localities. This points to at least one major barrier to gene flow for Parechinus angulosus along the South African coast, namely Cape Point. Several additional, smaller hindrances to gene flow along the coast were also identified, most of which are congruent with findings from studies on both other and sea urchin species. As a standalone study this research elucidated many aspects regarding the phylogeography of the Cape sea urchin, P. angulosus. However, it is when viewed in the broader context of invertebrate phylogeography along the southern African coastline that this research will provide its most critical insight.
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