The present longitudinal study examines a natural population of threespine sticklebacks, Gasterosteus aculeatus form Little Mud Lake in British Colombia, Canada to determine if individual fish within a given population exhibited a preference for finding prey on the bottom of the lake, prey floating in the water column of the lake, or prey in other microhabitats of the lake. Foraging behaviors were recorded to determine the presence of individual specialization within the focal sympatric population. Comparing the proportion of strikes on various microhabitats for multiple individuals shows that individual specialization is present within the focal population of sticklebacks. Data shows that some fish prefer the feed on benthic prey while others prefer to feed on prey found on the surface of the water. Diet preferences were also compared to morphology to determine if individual fish traits had a relationship to preferred foraging location. Length of the longest gill raker and protrusion length results showed a relationship to limnetic-like and benthic-like feeding behaviors. / text

Individual specialization occurs when individuals selectively consume a subset of their population's diet. Intraspecific diet variation can stabilize population and community dynamics, promote species coexistence, and increase ecosystem productivity. Ecological variation also provides the variability necessary for natural or sexual selection to act. Individual threespine stickleback select different prey from a shared environment, and this variation is not simply a result of sex, size, or spatial heterogeneity. I use longitudinal observation of stickleback foraging microhabitat to support more commonly used cross-sectional metrics. Among recaptured individuals there were correlations between microhabitat use and functional morphology, and microhabitat use and long term dietary differences between individuals. I quantify individual specialization across populations using cross-sectional sampling to understand how and why ecological variation may itself be variable. All populations showed significant individual specialization. Specialization varied between populations and this variation seems to be a long-term property of populations. Overall morphological variance was positively correlated with ecological variation. Ecological variation, like all types of heritable variation, provides raw material for evolutionary change. For example, lacustrine populations of stickleback are commonly under disruptive selection due to intraspecific competition for prey resources. Speciation with gene flow may be driven by a combination of positive assortative mating and disruptive selection, particularly if selection and assortative mating act on the same trait. We present evidence that stickleback exhibit assortative mating by diet, using the isotopes of males and eggs within their nests. In concert with disruptive selection, this assortative mating should facilitate divergence. However, the population remains phenotypically unimodal, highlighting the fact that assortative mating and disruptive selection do not guarantee evolutionary divergence and speciation. There are several not-mutually-exclusive mechanisms by which assortative mating by diet may occur in these populations, such as shared microhabitat preference among individuals of similar diet. Stable isotopes reveal diet differences between different nesting areas and among individuals using different nest habitat within a nesting area. Spatial segregation of diet types may generate some assortative mating, but is insufficient to explain the observed assortment strength. We therefore conclude that sticklebacks' diet-assortative mating arises primarily from behavioral preference rather than from spatial isolation. / text

<p>Habitat fragmentation and anthropogenic development influence the level of isolation and security in and around protected habitats affecting wolf movements and the distribution and abundance of their prey. In light of recent concern about the ecology of animals in protected areas, I initiated a research project to investigate the molecular and foraging ecology of grey wolves in and around Prince Albert National Park (PANP), Saskatchewan. <p>Estimates of genetic diversity and population structure can be used as surrogates to detect effects of habitat degradation on wolves. Genetic diversity was high in these populations relative to other North American wolf populations. My results suggest that wolves in central Saskatchewan form a panmictic population, however there is some evidence showing partial isolation of one group of wolves within PANP. I speculate that the level of human activity such as road networks, hunting, and trapping act as dispersal impediments to this isolated group. Further, the genetic homogenization, indicating high population turnover, of wolf groups that use the periphery and adjacent areas of PANP may also contribute to the observed genetic subdivision. The partially isolated NW group, characterized by slightly lower diversity indices, low migration rates, and higher levels of allele fixation, indicated this group was a more stable social unit comprised of more related individuals.</p><p>Knowledge of wolf food habits and how they change over time is a fundamental component to understanding wolf ecology. Using scat analysis I evaluated wolf foraging ecology by calculating indices of occurrence/faeces (OF) and percent prey biomass contribution: white tailed deer contributed 43% and 33% respectively to wolf diet; elk (33%, 50%), moose (7%, 14%), beaver (5%, 2%), and snowshoe hare (2%, <1%). I found no evidence of livestock depredation nor did wolves prey on bison or caribou. There were no differences in OF indices between years. Prey selectivity was apparent in both years with wolves selecting elk and avoiding beaver. A diversity of ungulate prey are readily available to wolves in this system; however, scat analysis and tests for prey selection indicate a preference for elk. I presume this is a choice made to balance risk with profitability of food items in concordance with optimal foraging theory.</p><p>I examined trophic relationships between the grey wolf and 18 mammalian species from the boreal forest of central Saskatchewan, Canada, using ä13C and ä15N stable isotope values measured in hair samples. Variance in isotope values for wolves and other carnivores was investigated as a proxy for dietary variation. IsoSource, an isotopic source partitioning model, quantified the relative proportions of 5 most likely prey items in the diets of wolves.</p><p>I compared these results with investigations of faecal contents using percent biomass contributions of prey items in wolf diet. I found no difference between percent biomass measures and mean percent contributions derived from IsoSource. Despite social foraging, my results indicate highly variable diets among individual wolves and I discuss this in terms of boreal wolf ecology.

<p>Habitat fragmentation and anthropogenic development influence the level of isolation and security in and around protected habitats affecting wolf movements and the distribution and abundance of their prey. In light of recent concern about the ecology of animals in protected areas, I initiated a research project to investigate the molecular and foraging ecology of grey wolves in and around Prince Albert National Park (PANP), Saskatchewan. <p>Estimates of genetic diversity and population structure can be used as surrogates to detect effects of habitat degradation on wolves. Genetic diversity was high in these populations relative to other North American wolf populations. My results suggest that wolves in central Saskatchewan form a panmictic population, however there is some evidence showing partial isolation of one group of wolves within PANP. I speculate that the level of human activity such as road networks, hunting, and trapping act as dispersal impediments to this isolated group. Further, the genetic homogenization, indicating high population turnover, of wolf groups that use the periphery and adjacent areas of PANP may also contribute to the observed genetic subdivision. The partially isolated NW group, characterized by slightly lower diversity indices, low migration rates, and higher levels of allele fixation, indicated this group was a more stable social unit comprised of more related individuals.</p><p>Knowledge of wolf food habits and how they change over time is a fundamental component to understanding wolf ecology. Using scat analysis I evaluated wolf foraging ecology by calculating indices of occurrence/faeces (OF) and percent prey biomass contribution: white tailed deer contributed 43% and 33% respectively to wolf diet; elk (33%, 50%), moose (7%, 14%), beaver (5%, 2%), and snowshoe hare (2%, <1%). I found no evidence of livestock depredation nor did wolves prey on bison or caribou. There were no differences in OF indices between years. Prey selectivity was apparent in both years with wolves selecting elk and avoiding beaver. A diversity of ungulate prey are readily available to wolves in this system; however, scat analysis and tests for prey selection indicate a preference for elk. I presume this is a choice made to balance risk with profitability of food items in concordance with optimal foraging theory.</p><p>I examined trophic relationships between the grey wolf and 18 mammalian species from the boreal forest of central Saskatchewan, Canada, using ä13C and ä15N stable isotope values measured in hair samples. Variance in isotope values for wolves and other carnivores was investigated as a proxy for dietary variation. IsoSource, an isotopic source partitioning model, quantified the relative proportions of 5 most likely prey items in the diets of wolves.</p><p>I compared these results with investigations of faecal contents using percent biomass contributions of prey items in wolf diet. I found no difference between percent biomass measures and mean percent contributions derived from IsoSource. Despite social foraging, my results indicate highly variable diets among individual wolves and I discuss this in terms of boreal wolf ecology.

This Ph.D. Thesis is focused mainly on the biology of two typical European predatory fishes, European catfish (Silurus glanis) and perch (Perca fluviatilis). Catfish is a typical apex predator, whereas perch is a smaller species that plays role of a mesopredator. Although, catfish is the third largest freshwater fish in the world, only few studies dealing with this species have been revealed thus far. The main reason is connected with capturing of the species that is inefficient by standard ichthyologic methods. Studies, that have been revealed recently, focused mainly on expansions of catfish to the West and South Europe. Catfish is unwanted in these localities due to a potential negative impact on native fish community, thus its reduction is desirable. In contrast, catfish occurrence is important in native localities where it plays a key role as a biomanipulative species (I). Catfish is a true generalist, which is a typical feature for large-bodied apex predators connected with high energy consumption of their bodies. The second typical feature is a wide diet plasticity and thus good adaptability to new food sources. It is associated with distribution of various food sources among individuals within the population (II). By contrast, perch is one of the most studied fish in the world and hundreds of studies with IF are revealed every year. However, the more information about biology of perch have been known, the more questions have been arisen. Several phenomena are revealed also in this thesis. For instance, crucial impact of juvenile perch on the entire ecosystem is described. High predation pressure on zooplankton may induce piscivory in primarily zooplanktivorous fish (III). Further, juvenile perch utilize hypoxic pelagic zones as a refuge against predation (IV). The last surprising phenomenon is described in the study dealing with both species, catfish and perch. Their coexistence may lead in strong discrimination of one species caused by special predation that was supposed to be implausible (V).

Master of Science / Biology / Michael Tobler / Environmental variation can shape phenotypic variation in organisms. Most evidence for trait differentiation along environmental gradients comes from analyses of dichotomous habitat types that differ in only one or few environmental factors. In reality, however, environmental variation is often more subtle, gradual, and multifarious. I investigated geographic variation in body shape, trophic resource use, and individual diet specialization in two species of darters (Etheostoma spectabile and E. flabellare; Percidae) that occur along river gradients. I explicitly tested how abiotic and biotic environmental factors shape trait variation within and between species. Results indicated significant among population variation in the body shape of both species. Population differences in body shape were correlated with variation in substrate composition. Although body shape analyses revealed a small but significant signal of convergent evolution of body shape when both species occur in sympatry, E. spectabile and E. flabellare mostly exhibited unique responses to shared sources of selection. The analyses of darter trophic resource use uncovered significant resource partitioning between the two species and geographic variation in diets that is likely driven by differences in resource availability. Furthermore, the majority of populations exhibited significant individual specialization. Variation in individual specialization in populations of E. flabellare was related to invertebrate density and competitor richness, and in E. spectabile to the combined effects of invertebrate density and invertebrate diversity. My results indicate substantial variation in trophic resource use among individuals, populations, and species of small-bodied fishes that are typically assumed to be generalist insectivores. Variation in diet specialization may be more widespread than previously considered, and ecological opportunity is an important factor in shaping trophic resource use of individuals and populations. Overall, the results indicate that even subtle and gradual environmental variation can induce substantial variation in phenotypes on a relatively small spatial scale.

Made available in DSpace on 2014-12-17T14:10:28Z (GMT). No. of bitstreams: 1 ThiagoCSOP_DISSERT.pdf: 1144782 bytes, checksum: be3dbb51350da1787be38ffb793e4e0a (MD5) Previous issue date: 2012-09-26 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / Historically, ever since the pre-Darwinian naturalists interspecific competition was considered the main force responsible for structuring ecological communities. This interpretation lost strength in the late 70s and throughout the 80s giving room for other views, which consider other factors such as predation, parasitism and the phylogenetic inertia more important. Studies on changes in the trophic niche of a species are still uncommon in general and especially in amphibians. Species considered generalist might actually be a group of individual specialists, or individuals that specialize in a particular category of prey during a period of scarcity of resources, thus reducing intraspecific competition. This work studied the community structure of litter amphibians and trophic variation along the dry and rainy seasons in a population of Leptodactylus macrosternum. Sixteen-litter frog species were studied for their diet. Two central assumptions were tested: 1a) if the community is structured in the niche trophic level, and 1b) if there is a significant difference in the use of food resources by different species (i.e. if the community is structured), the observed structure is the result of ecological interactions or just the current phylogenetic inertia of species. Finally, 2) if there is variation in food resource use between seasons for L. macrosternum. The community showed a structure with respect to the use of food resources, and this structure persisted after taking into account the phylogenetic relationships among species. The diet of Leptodactylus macrosternum varied with the seasons, with a significant degree of individual specialization for the dry season. Patterns of a local community are important to understand its dynamics, and this may play a role in larger- scale processes. Therefore, the studies in community ecology are fundamental to understand and eventually restoring degraded areas / Historicamente, a competi??o interespec?fica foi considerada a principal for?a ecol?gica respons?vel pela estrutura??o de comunidades. Essa interpreta??o perdeu for?as no final dos anos 70 e ao longo dos anos 80 e deu espa?o para outras vis?es, onde fatores como preda??o, parasitismo e a in?rcia filogen?tica mostraram-se importantes. Estudos sobre varia??es intraespec?ficas do nicho tr?fico s?o pouco comuns de uma forma geral e principalmente em anf?bios. Esses estudos tem mostrado que esp?cies antes chamadas generalistas podem ser, na verdade, um grupo de indiv?duos especialistas, ou ainda indiv?duos que se especializam em uma determinada categoria de presa durante um per?odo de escassez de recursos, reduzindo assim a competi??o intraespec?fica. O presente trabalho ? dividido em dois cap?tulos. No primeiro n?s estudamos a estrutura??o tr?fica da taxocenose de anf?bios. Para tanto, n?s analisamos a dieta de 16 esp?cies de anuros de serapilheira. Os dados foram usados para avaliar duas perguntas: 1a) se a comunidade est? estruturada no nicho tr?fico e 1b) em que grau a estrutura observada ? fruto de intera??es ecol?gicas atuais e da in?rcia filogen?tica das esp?cies em quest?o. No segundo cap?tulo n?s estudamos a varia??o tr?fica da esp?cie Leptodactylus macrosternum e testamos se existe varia??o no uso dos recursos alimentares entre os per?odos seco e chuvoso. A comunidade mostrou estrutura??o com rela??o ao uso dos recursos alimentares e esta estrutura??o ? influenciada pelas rela??es filogen?ticas entre as esp?cies. A dieta de Leptodactylus macrosternum variou conforme os per?odos seco e chuvoso, com um grau de especializa??o individual significativo para o per?odo seco. A din?mica de uma comunidade local pode atuar em processos de maior escala. Logo, o estudo de comunidades ? fundamental para se entender e eventualmente restaurar ?reas degradadas

Orientadores: Sergio Furtado dos Reis, Glauco Machado / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-09T02:04:21Z (GMT). No. of bitstreams: 1 Araujo_MarcioSilva_D.pdf: 2407731 bytes, checksum: 8775de8c335558a4381e1293aad0f17e (MD5) Previous issue date: 2007 / Resumo: A teoria ecológica clássica, em especial a teoria de nicho, foi construída sob a suposição de que os indivíduos de uma população são equivalentes em termos da utilização de recursos. Entretanto, é sabido que os indivíduos de uma população podem variar no uso de recursos e que essa variação pode ter importantes implicações ecológicas e evolutivas. Essa variação interindividual pode dar origem a morfotipos discretos (¿polimorfismo de recursos¿) ou ser contínua (¿especialização individual¿). O presente estudo teve como objetivo investigar a variação interindividual no uso de recursos em quatro populações de rãs do Cerrado brasileiro (Leptodactylus sp., L. fuscus, Eleutherodactylus cf. juipoca e Proceratophrys sp.), uma população de vespas-caçadoras de uma área de Mata Atlântica (Trypoxylon albonigrum) e uma população do peixe lacustre Gasterosteus aculeatus da Columbia Britânica, Canada. Houve evidência de variação interindividual em todas as populações estudadas, indicando que esse fenômeno não é exclusivo de comunidades temperadas de baixa diversidade. Houve uma associação entre a amplitude dos nichos populacionais e o grau de variação interindividual, indicando que os nichos individuais permanecem estreitos apesar da expansão do nicho populacional. Esse padrão é consistente com a presença de trade-offs funcionais associados ao uso dos recursos. A base dos trade-offs permanece desconhecida no caso das rãs e das vespas, mas é provavelmente comportamental. No caso de G. aculeatus, os trade-offs têm base morfológica, mas são mediados pelo comportamento. Além disso, foi identificado um padrão de partição de recursos inédito nesses peixes, em que os indivíduos formam microguildas que representam subdivisões dos recursos litorâneos e pelágicos. São propostos dois novos métodos para a investigação da variação intrapopulacional no uso de recursos, um deles baseado no uso de isótopos estáveis de carbono (d13C) e o outro na teoria de redes complexas / Abstract: Ecological theory, and specially niche theory, was built on the assumption that individuals are equivalent in terms of resource use. However, the individuals in a population may vary in their resources, and this interindividual variation may have important ecological and evolutionary implications. Such variation may give rise to discrete morphological groups (¿resource olymorphism¿) or it may be more continuous (¿individual specialization¿). In the present study, we investigated interindividual variation in resource use in four populations of frogs inhabiting the Brazilian Cerrado (Leptodactylus sp., L. fuscus, Eleutherodactylus cf. juipoca e Proceratophrys sp.), one population of hunting-wasp of the Atlantic Rainforest (Trypoxylon albonigrum), and one population of sticklebacks (Gasterosteus aculeatus) from British Columbia, Canada. We found evidence of interindividual diet variation in all studied populations, indicating that such variation is not restricted to temperate, depauperate comunities. There was an association between niche width and the degree of interindividual variation, indicating that individual niches remain constrained as the population niche expands. This pattern is consistent with the presence of functional trade-offs associated with resource use. In the case of the frogs and the wasps, the nature of the trade-offs remains unknown, but are likely to be behavioral. In the sticklebacks, the trade-offs have a morphological basis, but are mediated by behavior. We found that individual sticklebacks partition resources within littoral and within pelagic prey, which represents a finer pattern of resource partitioning than the traditional ¿littoral-pelagic¿ dichotomy. Two new methods for the quantification of interindividual diet variation are proposed, one based on carbon stable isotopes (d13C) and another based on complex-network theory / Doutorado / Ecologia / Doutor em Ecologia

Orientadores: Sérgio Furtado dos Reis, Marco Aurelio Ribeiro de Mello / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-19T19:33:41Z (GMT). No. of bitstreams: 1 Rogeri_PatriciaKerches_M.pdf: 2667318 bytes, checksum: dc499b718c54abfc2ceccc3f989caae8 (MD5) Previous issue date: 2011 / Resumo: Estudos recentes têm sugerido especialização individual no uso de diferentes recursos por populações de animais. Em paisagens heterogêneas, é provável que ocorra também especialização individual no uso do espaço. Para testar essa hipótese, estudei uma população do morcego frugívoro Sturnira lilium (Chiroptera: Phyllostomidae) em uma área de cerrado no sudeste do Brasil. Testei também a previsão de que o uso das áreas pelos morcegos deve estar relacionado com a diferenças na distribuição espacial das principais plantas-alimento na área. Monitorei por radiotelemetria 13 indivíduos de S. lilium de junho a agosto de 2009 e de junho a agosto de 2010. Para medir a variação interindividual no uso do espaço, usei uma metodologia baseada em redes complexas. Com uma imagem de satélite de alta resolução da área de estudo, determinei 13 subáreas de acordo com o tipo predominante de habitat. Nessas subáreas, estimei a densidade das principais plantas-alimento de S. lilium e contei o número de pontos de atividade estimados para cada indivíduo. As áreas de uso totais estimadas variaram de 4 a 457 ha (110 ± 126,8). Observei grande variação interindividual no uso de áreas nucleares de forrageio (E = 0,80; P < 0,001), porém sem agrupamento ou superdispersão (Cws = -0,115; P = 1). A variação encontrada não foi explicada por sexo ou peso. Dois indivíduos concentraram sua atividade em subáreas com maior densidade de Solanaceae, quatro em subáreas com maior densidade de Piperaceae, e um em subáreas com maior densidade de Cecropiaceae. Estes resultados corroboram a hipótese de especialização individual no uso do espaço pela população de S. lilium estudada, estando a especialização aparentemente ligada à distribuição espacial das plantas-alimento. Essa variação interindividual pode ter consequências sobre a forma como morcegos S.lilium prestam serviços ambientais de dispersão de sementes e conectam elementos de paisagens fragmentadas / Abstract: Recent studies have pointed out individual specialization in resource use in animal populations. In heterogeneous landscapes, there is probably also individual specialization in the use of space. To test this hypothesis, I studied a population of the frugivorous bat Sturnira lilium (Chiroptera: Phyllostomidae) in a cerrado area in southeastern Brazil. I also tested the prediction that the use of areas by bats should be related to differences in spatial distribution among the main food-plants. Thirteen S. lilium bats were radiotracked in June-August 2009 and June-August 2010. To measure individual specialization in space use I used an approach based on network theory. With a high-resolution satellite image of the study area, I determined 13 subareas according to predominant habitat type. In these subareas, I estimated the density of the main food-plants of S. lilium and counted the number of activity points estimated for each individual bat. The estimated total areas of use varied from 4 to 457 ha (110 ± 126,8). I observed large interindividual variation in the use of core foraging areas (E = 0,80; P < 0,001) but no clustering or overdispersion (Cws = -0,115; P = 1). The variation found was not explained by sex or weight. Two individuals concentrated their activity in subareas with higher density of Solanaceae, four in subareas with higher density of Piperaceae, and one in subareas with higher density of Cecropiaceae. These results corroborate the hypothesis of individual specialization in the use of space by the S. lilium population studied, which seems to be linked to uneven distribution of food-plants. This interindividual variation may affect the way S. lilium provides environmental services of seed dispersal and connect elements of fragmented landscapes / Mestrado / Ecologia / Mestre em Ecologia

Top predators can have large effects on community and population dynamics but we still know relatively little about their roles in ecosystems and which biotic and abiotic factors potentially affect their behavioral patterns. Understanding the roles played by top predators is a pressing issue because many top predator populations around the world are declining rapidly yet we do not fully understand what the consequences of their potential extirpation could be for ecosystem structure and function. In addition, individual behavioral specialization is commonplace across many taxa, but studies of its prevalence, causes, and consequences in top predator populations are lacking. In this dissertation I investigated the movement, feeding patterns, and drivers and implications of individual specialization in an American alligator (Alligator mississippiensis) population inhabiting a dynamic subtropical estuary. I found that alligator movement and feeding behaviors in this population were largely regulated by a combination of biotic and abiotic factors that varied seasonally. I also found that the population consisted of individuals that displayed an extremely wide range of movement and feeding behaviors, indicating that individual specialization is potentially an important determinant of the varied roles of alligators in ecosystems. Ultimately, I found that assuming top predator populations consist of individuals that all behave in similar ways in terms of their feeding, movements, and potential roles in ecosystems is likely incorrect. As climate change and ecosystem restoration and conservation activities continue to affect top predator populations worldwide, individuals will likely respond in different and possibly unexpected ways.