With the contribution of intraspecific trait variation (ITV) to ecological processes being increasingly appreciated, its role in defining niche characteristics arises as a topic of interest. I hypothesised that species with a high magnitude of ITV would occupy a larger climate niche breadth than species with little ITV. Trait and occurrence data for 211 angiosperm tree species across Puerto Rico was used to investigate this hypothesis. Multiple indices for climate niche breadth (NB) and intraspecific variation were calculated, after which regression tests were performed to identify and characterise any relationships between NB and ITV. I found consistent positive correlations between niche breadth and intraspecific variation values (a single negative result was present), supporting the hypothesis that ITV of functional traits has a positive influence on climate niche breadth. These results highlight the contribution of ITV to species distribution, though the mechanisms behind this relationship are unclear and present a question for future study.

Climate change is expected to have a profound impact on freshwater fish communities, especially at higher latitudes. In this study I investigated potential effects of climate change on the niche structure of Eurasian perch (Perca fluviatilis) by looking at their diet across a latitudinal gradient and at varying light climate. Dietary niche width of Eurasian perch did not differ significantly between boreal and temperate latitudes. Additionally, no significant difference in the prevalence of specialist individuals was found along the latitudinal gradient and water transparency levels. Habitat was the main factor that significantly affected niche width and level of specialization with both being significantly higher in the littoral habitat. Taken together my results suggest that climate change might indirectly affect niche patterns by altering fish densities through changes in productivity resulting in niche and specialization variation among habitats.

Submitted by Jean Medeiros (jeanletras@uepb.edu.br) on 2016-02-29T13:53:28Z No. of bitstreams: 2 license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) PDF - Natalice dos Santos Sales.pdf: 3971336 bytes, checksum: 5c5a0633dc255180a572d2b151d73426 (MD5) / Approved for entry into archive by Secta BC (secta.csu.bc@uepb.edu.br) on 2016-06-13T20:31:10Z (GMT) No. of bitstreams: 2 PDF - Natalice dos Santos Sales.pdf: 3971336 bytes, checksum: 5c5a0633dc255180a572d2b151d73426 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) / Made available in DSpace on 2016-06-13T20:31:10Z (GMT). No. of bitstreams: 2 PDF - Natalice dos Santos Sales.pdf: 3971336 bytes, checksum: 5c5a0633dc255180a572d2b151d73426 (MD5) license_rdf: 23148 bytes, checksum: 9da0b6dfac957114c6a7714714b86306 (MD5) Previous issue date: 2015-02-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Hypersaline estuarine systems the fish species move between areas of greater supply of resources and according to salinity gradient, because the physiological tolerance is a common adaptation to many species of estuarine fish. Moreover, those species can display other behavioral adaptations, such as food flexibility. Thus, this study analized structure and composition of the ichthyofauna in accordance with the salinity gradients as well as ecology and trophic organization. Samples were collected in rainy and dry season, from January to Decembre 2012, in 12 points distributed into three areas defined according to the salinity gradient (Inferior, Intermediate and Upper). The fishes were captured using a beach seine. The low rainfall, high evaporation rate and the small input of freshwater in Tubarão River estuary favored a salinity between 30 and 45. The structure and composition of ichthyofauna showed spatial and temporal differences between the Tubarão River estuary areas, with salinity and substrate influencing the distribution of species. Atherinella brasiliensis, Lile piquitinga, Eucinostomus argenteus, Ulaema lefroyi, Lutjanus analis and Sphoeroides greeleyi are the most abundant distributed in all the estuarine areas. Among the 104 species caught at the estuary of Tubarão River, 18 were selected according to their abundance, for analysis of trophic ecology. However, only the spacial variation showed significant changes in fish diet. In general, the diet of the species was based mainly on Macroalgae, Polychaeta, Decapoda, Mollusca and Zooplankton. Among these items the representatives of Zooplankton are the main prey in the diet of small juveniles. Because of this preference for certain food items species were grouped into six different trophic guilds: Zooplanktivore, Omnivore, Herbivore-Macroalgae, Zoobenthivore- Hyperbenthos, Zoobenthivore-Epifauna and Zoobenthivore-Infauna. The largest overlap values occured in the Upper zone, due to a higher salinity restricting the establishment of various prey. The results presented in this study showed the direct relationship of the structure and composition of ichthyofauna and the trophic ecology with habitat heterogeneity and the variation in salinity. Thus, the data obtained in the study allows our understanding of the dynamics of community structure that hypersaline system and favors the development of approaches to conservation and sustainable use of biological diversity. / Nos sistemas estuarinos hipersalinos as espécies de peixes se movimentam entre os locais de maior oferta de recursos e entre os diferentes gradientes de salinidade, de acordo com a tolerância fisiológica que é uma adaptação comum para espécies de peixes estuarinos. Além disso, estas espécies podem exibir outras adaptações comportamentais, como a flexibilidade alimentar. Assim, o estudo analisou a estrutura e composição da ictiofauna de acordo com o gradiente de salinidade, bem como a ecologia e a organização trófica. As amostragens foram realizadas durante a chuva e a seca de 2012 em 12 pontos distribuídos em três zonas definidas de acordo com o gradiente de salinidade (Inferior, Intermediária e Superior). Os peixes foram capturados com a utilização de uma rede beach seine através de arrasto de praia. O baixo índice pluviométrico, a elevada taxa de evaporação e a pequena entrada de água doce presentes no estuário do Rio Tubarão favoreceram uma salinidade entre 30 e 45. A estrutura e composição da ictiofauna apresentaram diferenças espacial e temporal entre as zonas do estuário do rio Tubarão, com a salinidade e o substrato influenciando na distribuição das espécies Atherinella brasiliensis, Lile piquitinga, Eucinostomus argenteus, Ulaema lefroyi, Lutjanus analis and Sphoeroides greeleyi Dentre as 104 espécies capturadas no estuário do Rio Tubarão 18 foram selecionadas, de acordo com sua abundância, para análise da ecologia trófica. No geral a dieta das espécies foi baseada, principalmente, em Macroalgas, Polychaeta, Decapoda, Mollusca e Zooplâncton. Dentre esses itens os representantes do Zooplâncton são as presas principais na dieta dos pequenos juvenis. Devido a essa preferência por determinados itens alimentares as espécies foram agrupadas em seis guildas tróficas, distintas: Zooplanctívoro, Onívoro. HerbívoroMacroalga, Zoobentívoro-Hiperbentos, Zoobentívoro-Epifauna e Zoobentívoro-Infauna. Os maiores valores de sobreposição foram registrados na zona Superior, possivelmente pela elevada salinidade que restringe o estabelecimento de diversas presas. Em geral os resultados apresentados nesse estudo mostram a relação direta da estrutura e composição da ictiofauna e a ecologia trófica das espécies com a heterogeneidade do habitat e a variação de salinidade que possibilita proteção aos peixes juvenis e maior abundância de recursos tróficos. Assim, os dados obtidos no estudo possibilita a compreensão da dinâmica da estrutura da comunidade desse sistema hipersalino, bem como favorece o desenvolvimento de abordagens para a conservação e uso sustentável da diversidade biológica.

Made available in DSpace on 2016-06-02T19:31:59Z (GMT). No. of bitstreams: 1 4017.pdf: 3689983 bytes, checksum: f15b289ba85e2141d06ae104015f2757 (MD5) Previous issue date: 2011-06-07 / The trophic ecology is one of the most important aspects to understand the role of a species in the community and in the ecosystem functioning. Studies regarding the feeding of fishes coupled to the ecomorphology of a species become important tools in understanding their ecological role and position in the environment. The present study aimed to analyze the types and amount of food consumed by eleven species of fishes collected in six streams of Alcântara, Maranhão state, and assess their possible interspecific interactions. The specimens were collected in the rainy season, in January, and in the dry season, in November 2008. The analysis of morphology of the fish species was performed by measuring 17 characteristics and calculating 16 ecomorphological attributes. Analysis of the contents of the digestive tract was performed quantitatively and qualitatively. In order to determine the feeding habits of each species the frequency of occurrence, volume and alimentary index of each food item consumed were calculated. The majority of individuals analyzed was collected in the streams Igarapé do Camarajó and Igarapé do Brito. The trophic structure of fish assemblages of these two streams was diversified in both, rainy and dry seasons. The habit of the benthivore species Micropoecilia cf. parae and Apistogramma cf. piauienses was corroborated by their morphology. In the rainy season, there was a higher niche overlap in the diet of insectivorous species in the stream Igarapé do Camarajó, but the morphology of these species showed distinct spatial occupation of the habitat, thus allowing their coexistence. In the dry season most species had food overlap due to the consumption of organic detritus in the Igarapé do Camarajó stream and due to the consumption of chironomid larvae in the Igarapé do Brito stream. Fishes of Camarajó and Brito streams were more likely to feeding specialization in the rainy season and increased diversification of the items consumed during the dry season, indicated, respectively, by larger and smaller niche breadth. The changes in the trophic structure, in the niche overlap and in the niche breadth of fish community in the six streams studied indicate that fluctuations on the hydrological cycle in these streams are an important factor in the throphic dynamics of these fish communities. / Um dos aspectos mais relevantes no entendimento do papel de uma espécie na comunidade à qual pertence e no funcionamento nos ecossistemas refere-se à sua ecologia trófica. Estudos sobre a alimentação de peixes atrelados à ecomorfologia das espécies são ferramentas importantes no entendimento do papel ecológico das espécies e de sua ocupação do meio. O presente estudo teve como objetivos estudar as características da alimentação e da ecomorfologia da ictiofauna amostrada em seis igarapés maranhenses e avaliar suas possíveis interações interespecíficas. Os exemplares analisados foram coletados na estação chuvosa, em janeiro, e na estação seca, em novembro, de 2008. Para análise da ecomorfologia destas espécies foram obtidas 17 medidas e com elas calculados 16 atributos ecomorfológicos. A análise do conteúdo do tubo digestório foi realizada quali e quantitativamente. Para a determinação do hábito alimentar de cada espécie foram calculados a frequência de ocorrência, o volume e o índice alimentar de cada item consumido. A maioria dos indivíduos analisados foi coletada nos igarapés do Camarajó e do Brito. A estrutura trófica da assembléia de peixes destes dois igarapés foi diversificada em ambas estações, chuvosa e seca. O hábito bentófago das espécies Micropoecilia cf. parae e Apistogramma cf. piauiensis foi corroborada por suas morfologias. Na estação chuvosa, observou-se maior sobreposição de nicho na dieta dos insetívoros no igarapé do Camarajó, porém, os atributos ecomofológicos destas espécies indicaram distinta ocupação de nicho espacial entre elas, permitindo, assim, a coexistência. Já na estação seca, no igarapé do Camarajó, a maioria das espécies teve sobreposição alimentar devido ao consumo de detritos orgânicos e no igarapé do Brito pelo consumo de quironomídeos. Os peixes dos igarapés do Camarajó e do Brito apresentaram maior tendência à especialização alimentar na estação chuvosa e maior diversificação dos itens consumidos na estação seca, ambas indicadas pela maior e menor amplitude de nicho, respectivamente. As mudanças na estrutura trófica, na sobreposição e no espectro alimentar da ictiofauna dos seis igarapés maranhenses estudados, indicam que as flutuações decorrentes do ciclo hidrológico constituem, nestes igarapés, um fator importante na dinâmica destas comunidades de peixes.

Made available in DSpace on 2014-12-17T15:37:15Z (GMT). No. of bitstreams: 1 RaulFDS_DISSERT.pdf: 3514530 bytes, checksum: 5a7cb4478b93d4050ccdf9c56e02ddbb (MD5) Previous issue date: 2013-03-27 / Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior / This study investigated the influence of intrinsic and extrinsic factors on the feeding ecology and foraging behavior of the whiptail lizard Ameivula aff. ocellifera, a new species widely distributed in the Brazilian Caatinga, and that is in process of description. In attendance to the objectives, the Dissertation was structured in two chapters, which correspond to scientific articles, one already published and the other to be submitted for publication. In Chapter 1 were analyzed the general diet composition, the relationship between lizard size and prey size, and the occurrence of sexual and ontogenetic differences in the diet. Chapter 2 contemplates a seasonal analysis of diet composition during two rainy seasons interspersed with a dry season, and the quantitative analysis of foraging behavior during two distinct periods. The diet composition was determined through stomach analysis of lizards (N = 111) collected monthly by active search, between September 2008 and August 2010, in the Esta??o Ecol?gica do Serid? (ESEC Serid?), state of Rio Grande do Norte. Foraging behavior was investigated during a rainy and a dry month of 2012 also in ESEC Serid?, by determining percent of time moving (PTM), number of movements per minute (MPM) and prey capture rate by the lizards (N = 28) during foraging. The main prey category in the diet of Ameivula aff. ocellifera was Insect larvae, followed by Orthoptera, Coleoptera and Araneae. Termites (Isoptera) were important only in numeric terms, having negligible volumetric contribution (<2%) and low frequency of occurrence, an uncommon feature among whiptail lizards. Males and females did not differ neither in diet composition nor in foraging behavior. Adults and juveniles ingested similar prey types, but differed in prey size. Maximum and minimum prey sizes were positively correlated with lizard body size, suggesting that in this population individuals experience an ontogenetic change in diet, eating larger prey items while growing, and at the same time excluding smaller ones. The diet showed significant seasonal differences; during the two rainy seasons (2009 and 2010), the predominant prey in diet were Insect larvae, Coleoptera and Orthoptera, while in the dry season the predominant prey were Insect larvae, Hemiptera, Araneae and Orthoptera. The degree of mobility of consumed prey during the rainy seasons was lower, mainly due to a greater consumption of larvae (highly sedentary prey) during these periods. Population niche breadth was higher in the dry season, confirming the theoretical prediction that when food is scarce, the diets tend to be more generalized. Considering the entire sample, Ameivula aff. ocellifera showed 61,0 ? 15,0% PTM, 2,03 ? 0,30 MPM, and captured 0,13 ? 0,14 per minute. Foraging mode was similar to that found for other whiptail lizards regarding PTM, but MPM was relatively superior. Seasonal differences were verified for PTM, which was significantly higher in the rainy season (66,4 ? 12,1) than in the dry season (51,5 ? 15,6). It is possible that this difference represents a behavioral adjustment in response to seasonal variation in the abundance and types of prey available in the environment in each season / Este estudo investigou a influ?ncia de fatores intr?nsecos e extr?nsecos sobre a ecologia alimentar e o comportamento de forrageamento do lagarto cauda-de-chicote (whiptail) Ameivula aff. ocellifera, uma esp?cie nova com ampla distribui??o na Caatinga, e que est? em fase de descri??o. Em atendimento aos objetivos, a Disserta??o foi estruturada na forma de dois cap?tulos, os quais correspondem a artigos cient?ficos, um j? publicado e o outro a ser submetido ? publica??o. No Cap?tulo 1 s?o analisadas a composi??o geral da dieta, a rela??o entre o tamanho corporal dos lagartos e o tamanho das presas consumidas, e a ocorr?ncia de diferen?as sexuais e ontogen?ticas na dieta. O Cap?tulo 2 contempla a composi??o da dieta em termos sazonais, durante duas esta??es chuvosas intercaladas por uma esta??o seca, e an?lise quantitativa do comportamento de forrageamento durante dois per?odos distintos. A composi??o da dieta foi identificada atrav?s da an?lise do conte?do estomacal de lagartos (N = 111) coletados mensalmente por busca ativa entre setembro de 2008 e agosto de 2010, na Esta??o Ecol?gica do Serid? (ESEC Serid?), estado do Rio Grande do Norte. O comportamento de forrageamento foi investigado durante um m?s chuvoso e um m?s seco do ano de 2012 tamb?m na ESEC Serid?, avaliando-se a porcentagem do tempo gasta em movimento (PTM), o n?mero de movimentos por minuto (MPM) e taxa de captura de presas pelos lagartos (N = 28) durante o forrageamento. A principal categoria de presa na dieta de Ameivula aff. ocellifera foi Larvas de insetos, seguido por Orthoptera, Coleoptera e Araneae. T?rmitas (Isoptera) foram importantes somente em n?mero, com contribui??o volum?trica desprez?vel (<2%) e baixa frequ?ncia de ocorr?ncia, um tra?o incomum entre os lagartos whiptails. Machos e f?meas n?o diferiram nem na composi??o da dieta nem no comportamento de forrageamento. Adultos e juvenis se alimentaram de categorias de presa similares, mas diferiram no tamanho das presas. Os tamanhos m?ximo e m?nimo das presas foram positivamente correlacionados com o tamanho dos lagartos, sugerindo que na popula??o estudada os indiv?duos sofrem uma mudan?a ontogen?tica na dieta, consumindo itens alimentares maiores ? medida que crescem, e ao mesmo tempo excluindo presas menores. A dieta apresentou diferen?as sazonais significativas; durante as duas esta??es chuvosas (2009 e 2010), as presas predominantes na dieta foram Larvas de inseto, Coleoptera e Orthoptera, enquanto na esta??o seca as presas predominantes foram Larvas de inseto, Hemiptera, Araneae e Orthoptera. O grau de mobilidade das presas consumidas durante as esta??es chuvosas foi menor, principalmente devido ao maior consumo de larvas (presas altamente sedent?rias) durante esses per?odos. A largura de nicho da popula??o foi maior na x esta??o seca, confirmando a predi??o te?rica de que quando o alimento ? escasso, as dietas tendem a ser mais generalizadas. Considerando a amostra total, Ameivula aff. ocellifera apresentou 61,0 ? 15,0% PTM, 2,03 ? 0,30 MPM, e capturou 0,13 ? 0,14 presas por minuto. O modo de forrageamento foi similar ao encontrado para outros lagartos whiptails quanto a PTM, mas MPM foi relativamente superior. Diferen?as sazonais foram verificadas quanto a PTM, que foi significativamente maior na esta??o chuvosa (66,4 ? 12,1) que na esta??o seca (51,5 ? 15,6). ? poss?vel que essa diferen?a represente um ajuste comportamental em resposta ? varia??o sazonal na abund?ncia e tipos de presas dispon?veis no ambiente nas diferentes esta??es

Submitted by Marlene Santos (marlene.bc.ufg@gmail.com) on 2016-05-04T19:47:04Z No. of bitstreams: 2 Dissertação - Helen Rosa da Silva - 2015.pdf: 1580503 bytes, checksum: b52d04d79b983417cb07f98a43ae918d (MD5) license_rdf: 19874 bytes, checksum: 38cb62ef53e6f513db2fb7e337df6485 (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2016-05-05T13:09:29Z (GMT) No. of bitstreams: 2 Dissertação - Helen Rosa da Silva - 2015.pdf: 1580503 bytes, checksum: b52d04d79b983417cb07f98a43ae918d (MD5) license_rdf: 19874 bytes, checksum: 38cb62ef53e6f513db2fb7e337df6485 (MD5) / Made available in DSpace on 2016-05-05T13:09:30Z (GMT). No. of bitstreams: 2 Dissertação - Helen Rosa da Silva - 2015.pdf: 1580503 bytes, checksum: b52d04d79b983417cb07f98a43ae918d (MD5) license_rdf: 19874 bytes, checksum: 38cb62ef53e6f513db2fb7e337df6485 (MD5) Previous issue date: 2015-03-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / Understanding how species are distributed across space and what determines where they live is one of the oldest goals in Ecology. The concept of niche is very closely related to this goal. In fact, environmental variables are frequently used to predict the potential distribution of species. Niche amplitude is an important concept which helps us to understand which part of the available environmental space each species occupies, and how much of their niches overlap. Here we used a measure of niche amplitude based on the minimum and maximum tolerances of terrestrial vertebrates (except reptiles) for each variable related to climate. We calculated a single measure of niche amplitude for each species by considering together all chosen environmental variables. We used this number to first investigate the presence of latitudinal gradient in niche amplitude across the study area, which comprised the whole terrestrial globe. There is a significant correlation between niche amplitude and latitude for Old World birds. Second we tried to identify some phylogenetic structure in niche amplitude for birds. For this goal, we calculated the pair-wise niche overlap, and then compared the degree of overlap with pair-wise phylogenetic distances. We found no relationship between niche overlap and phylogenetic distance. We conclude that the absence of phylogenetic signal in niche overlap is due to the high dispersion capability of birds in general. If species have a high geographic range, they consequently have high niche amplitude, and therefore high overlap rates. Finally, we found a clear tendency of positive local spatial autocorrelation in mean niche overlap, as neighbor cells tend to show similar rates of niche overlap between species. / Compreender os fatores que determinam a distribuição das espécies no espaço geográfico é uma das questões mais importantes em ecologia. O conceito de nicho é fortemente relacionado a essa questão. Não por acaso, variáveis ambientais são comumente usadas para inferir a distribuição potencial de espécies. Amplitude de nicho é uma medida importante que nos possibilita saber que proporção do espaço ambiental cada espécie ocupa. Assim, podemos também identificar que proporção do espaço ocupado por cada espécie, seu nicho, é sobreposta pelo nicho das espécies coexistentes. No presente trabalho utilizamos uma medida de amplitude de nicho específica baseada na soma das tolerâncias para cada variável climática utilizada. Utilizamos essa medida para investigar, primeiramente, a presença de estrutura espacial, especificamente gradiente latitudinal, na amplitude de nicho de vertebrados terrestres (exceto répteis), numa escala global. Apenas aves do Velho Mundo apresentaram amplitude de nicho negativamente associada à latitude. Posteriormente, investigamos a presença de estrutura filogenética na amplitude de nicho em Aves, baseados na hipótese de conservação de nicho. Para esse objetivo calculamos a sobreposição de nicho par-a-par e então correlacionamos essa medida com as distâncias filogenéticas. Não houve correlação entre proximidade filogenética e sobreposição de nicho. Tal resultado pode estar relacionado à grande capacidade de dispersão de aves. Se a área de ocupação geográfica é ampla, a amplitude das tolerâncias é em geral alta e consequentemente a sobreposição média entre diferentes espécies. Finalmente houve forte indício de autocorrelação espacial positiva na sobreposição média por célula entre células próximas, indicando que áreas próximas tendem a apresentar espécies com taxas semelhantes de sobreposição de nicho.

No description available.

Recruitment of pelagic fish populations is believed to be regulated during the planktonic larval stage due to high rates of mortality during the early life stages. Starvation is thought to be one of the main sources of mortality, despite the fact that there is rarely a strong correlation between the feeding success of larval fish and food availability as measured in the field. This lack of relationship may be caused in part by (i) inadequate sampling of larval fish prey and (ii) the use of total zooplankton abundance or biomass as proxies for larval food availability. Many feeding studies rely on measures of average prey abundance which do not adequately capture the variability, or patchiness, of the prey field as experienced by larval fish. Previous studies have shown that larvae may rely on these patches to increase their feeding success. I assess the variability in the availability of larval fish prey over a range of scales and model the small-scale distribution of prey in Conception Bay, Newfoundland. I show that the greatest variability in zooplankton abundance existed at the meter scale, and that larval fish prey were not randomly distributed within the upper mixed layer. This will impact both how well we can model the stochastic nature of larval fish cohorts, as well as how well we can study larval fish feeding from gut content analyses. Expanding on six years of previous lab and field studies on larval Radiated Shanny (Ulvaria subbifurcata) from Conception Bay, Newfoundland, I assess the feeding success, niche breadth (S) and weight-specific feeding rates (SPC, d-1) of the larvae to determine whether there are size-based patterns evident across the years. I found that both the amount of food in the guts and the niche breadth of larvae increased with larval size. There was a shift from low to high SPC with increasing larval size, suggesting that foraging success increases as the larvae grow. My results suggest that efforts should be made to estimate the variability of prey abundance at scales relevant to larval fish foraging rather than using large-scale average abundance estimates, since small-scale prey patchiness likely plays a role in larval fish feeding dynamics. In addition, the characteristics of zooplankton (density, size and behaviour) should be assessed as not all zooplankton are preyed upon equally by all sizes of larval fish. Overall, this thesis demonstrates that indices based on averages fail to account for the variability in the environment and in individual larval fish, which may be confounding the relationship between food availability and larval growth.

Recruitment of pelagic fish populations is believed to be regulated during the planktonic larval stage due to high rates of mortality during the early life stages. Starvation is thought to be one of the main sources of mortality, despite the fact that there is rarely a strong correlation between the feeding success of larval fish and food availability as measured in the field. This lack of relationship may be caused in part by (i) inadequate sampling of larval fish prey and (ii) the use of total zooplankton abundance or biomass as proxies for larval food availability. Many feeding studies rely on measures of average prey abundance which do not adequately capture the variability, or patchiness, of the prey field as experienced by larval fish. Previous studies have shown that larvae may rely on these patches to increase their feeding success. I assess the variability in the availability of larval fish prey over a range of scales and model the small-scale distribution of prey in Conception Bay, Newfoundland. I show that the greatest variability in zooplankton abundance existed at the meter scale, and that larval fish prey were not randomly distributed within the upper mixed layer. This will impact both how well we can model the stochastic nature of larval fish cohorts, as well as how well we can study larval fish feeding from gut content analyses. Expanding on six years of previous lab and field studies on larval Radiated Shanny (Ulvaria subbifurcata) from Conception Bay, Newfoundland, I assess the feeding success, niche breadth (S) and weight-specific feeding rates (SPC, d-1) of the larvae to determine whether there are size-based patterns evident across the years. I found that both the amount of food in the guts and the niche breadth of larvae increased with larval size. There was a shift from low to high SPC with increasing larval size, suggesting that foraging success increases as the larvae grow. My results suggest that efforts should be made to estimate the variability of prey abundance at scales relevant to larval fish foraging rather than using large-scale average abundance estimates, since small-scale prey patchiness likely plays a role in larval fish feeding dynamics. In addition, the characteristics of zooplankton (density, size and behaviour) should be assessed as not all zooplankton are preyed upon equally by all sizes of larval fish. Overall, this thesis demonstrates that indices based on averages fail to account for the variability in the environment and in individual larval fish, which may be confounding the relationship between food availability and larval growth.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / This dissertation presents information on (1) the advertisement and aggressive calls of Crossodactylus schmidti and on (2) the species diet and its relationship with prey availability. The study was conducted with populations from the Parque Estadual do Turvo, located in the northwestern region of Rio Grande do Sul, Brazil. The park has an area of 17,491.4 ha and constitutes the largest preserved remnant of Mesophytic Semideciduous Forest in the state of Rio Grande do Sul. The advertisement and aggressive calls of C. schmidti were described based on vocalizations of seven individuals recorded between October 2009 and February 2010. Compared to the advertisement calls described for other species of the genus, the advertisement call of C. schmidti differs in the temporal structure by having fewer notes per call and longer intervals between notes, and in the spectral structure by having lower values of dominant frequency. The aggressive call of C. schmidti is a variation of the advertisement call, which is similar to this in the note duration and dominant frequency values, but is a longer call, having fewer notes with longer intervals between them. The advertisement and aggressive calls of C. schmidti may be emitted separately, or the aggressive call may be followed by the advertisement call. The diet of C. schmidti was evaluated from September 2009 to March 2010, based on 93 stomach contents obtained by the technique of regurgitation (n= 80) and analysis of stomach contents of collected specimens (n= 13). In this study we determined the diet niche breadth, evaluated the relationship of diet composition with prey availability in the environment, and we also looked for ontogenetic and sexual changes and composition differences in the diet. Nineteen categories of prey were consumed, and ants, beetles and flies presented the highest importance values. Despite the varied diet, the diet niche breadth was low, with few prey categories predominantly consumed. Ants, flies and spiders were consumed in similar proportion to that estimated in the environment. There was no relationship between mouth width and length and/or volume of prey consumed, but the differences in diet composition between males and females, and between adults and juveniles, were significant. Considering the varied diet, the relationship between the most important items of diet with their availability in the environment, and the narrow niche breadth found, C. schmidti seems to be an opportunistic forager with feeding habits similar to other species of the genus. The similarities in the importance of items such as ants, beetles, flies and insect larvae in diet of C. schmidti and other species of the genus suggest a strong phylogenetic influence. / A presente dissertação apresenta informações sobre (1) o canto de anúncio e o canto agressivo de Crossodactylus schmidti, e sobre (2) a dieta da espécie e sua relação com a disponibilidade de presas. O estudo foi conduzido com populações do Parque Estadual do Turvo, localizado na região noroeste do Rio Grande do Sul, Brasil. O parque possui uma área de 17.491,4 ha e constitui o maior remanescente preservado de Floresta Estacional Semidecídua do estado do Rio Grande do Sul. Os cantos de anúncio e agressivo de C. schmidti foram descritos a partir de vocalizações de sete indivíduos gravadas entre outubro de 2009 e fevereiro de 2010. Comparado aos cantos de anúncio descritos para outras espécies do gênero, o de C. schmidti difere na estrutura temporal por apresentar menor número de notas por canto e maior intervalo entre as notas, e, na estrutura espectral, difere por apresentar menores valores de frequência dominante. O canto agressivo de C. schmidti é uma variação do canto de anúncio, sendo semelhante a este na duração das notas e nos valores de freqüência dominante, mas é um canto mais longo, possuindo menor número de notas e maior intervalo entre elas. O canto de anúncio e o canto agressivo de C. schmidti podem ser emitidos isoladamente ou pode ser emitido o canto agressivo seguido do canto de anúncio. A dieta de C. schmidti foi avaliada de setembro de 2009 a março de 2010, a partir de 93 conteúdos estomacais obtidos através da técnica de regurgitação (n= 80) e da análise dos conteúdos estomacais de espécimes coletados (n= 13). Nesse trabalho, determinamos a amplitude do nicho alimentar da espécie, avaliamos a relação da dieta com a disponibilidade de presas no ambiente e testamos as diferenças ontogenéticas e sexuais na composição da dieta. Dezenove categorias de presas foram consumidas, sendo formigas, besouros e dípteros as que apresentaram os maiores valores de importância. Apesar da dieta variada, a amplitude alimentar foi baixa, com poucas categorias de presas consumidas predominantemente. Formigas, dípteros e aranhas foram consumidas em proporção semelhante à estimada no ambiente. Não houve relação entre a largura da boca e o comprimento médio e/ou volume das presas consumidas, mas as diferenças na composição da dieta entre machos e fêmeas e entre adultos e juvenis foram significativas. Considerando a dieta variada, a relação entre os itens mais importantes da dieta com sua disponibilidade e a estreita amplitude do nicho alimentar, C. schmidti parece ser um forrageador oportunista de hábito alimentar similar aos de outras espécies do gênero. As semelhanças na importância de itens como formigas, besouros, dípteros e larvas de insetos na dieta C. schmidti e na de outras espécies do gênero sugere uma forte influência filogenética.