Freshwater fish diversity in the western Amazon basin shaped by Andean uplift since the Late Cretaceous.

South America is home to the highest freshwater fish biodiversity on Earth, and the hotspot of species richness is located in the western Amazon basin. The location of this hotspot is enigmatic, as it is inconsistent with the pattern observed in river systems across the world of increasing species richness towards a river's mouth. Here we investigate the role of river capture events caused by Andean mountain building and repeated episodes of flooding in western Amazonia in shaping the modern-day richness pattern of freshwater fishes in South America, and in Amazonia in particular. To this end, we combine a reconstruction of river networks since 80 Ma with a mechanistic model simulating dispersal, allopatric speciation and extinction over the dynamic landscape of rivers and lakes. We show that Andean mountain building and consequent numerous small river capture events in western Amazonia caused freshwater habitats to be highly dynamic, leading to high diversification rates and exceptional richness. The history of marine incursions and lakes, including the Miocene Pebas mega-wetland system in western Amazonia, played a secondary role.

Accelerated body size evolution in upland environments is correlated with recent speciation in South American freshwater fishes.

Speciation rates vary greatly among taxa and regions and are shaped by both biotic and abiotic factors. However, the relative importance and interactions of these factors are not well understood. Here we investigate the potential drivers of speciation rates in South American freshwater fishes, the most diverse continental vertebrate fauna, by examining the roles of multiple biotic and abiotic factors. We integrate a dataset on species geographic distribution, phylogenetic, morphological, climatic, and habitat data. We find that Late Neogene-Quaternary speciation events are strongly associated with body-size evolution, particularly in lineages with small body sizes that inhabit higher elevations near the continental periphery. Conversely, the effects of temperature, area, and diversity-dependence, often thought to facilitate speciation, are negligible. By evaluating multiple factors simultaneously, we demonstrate that habitat characteristics associated with elevation, as well as body size evolution, correlate with rapid speciation in South American freshwater fishes. Our study emphasizes the importance of integrative approaches that consider the interplay of biotic and abiotic factors in generating macroecological patterns of species diversity.

Landscape dynamics and diversification of the megadiverse South American freshwater fish fauna.

Landscape dynamics are widely thought to govern the tempo and mode of continental radiations, yet the effects of river network rearrangements on dispersal and lineage diversification remain poorly understood. We integrated an unprecedented occurrence dataset of 4,967 species with a newly compiled, time-calibrated phylogeny of South American freshwater fishes-the most species-rich continental vertebrate fauna on Earth-to track the evolutionary processes associated with hydrogeographic events over 100 Ma. Net lineage diversification was heterogeneous through time, across space, and among clades. Five abrupt shifts in net diversification rates occurred during the Paleogene and Miocene (between 30 and 7 Ma) in association with major landscape evolution events. Net diversification accelerated from the Miocene to the Recent (c. 20 to 0 Ma), with Western Amazonia having the highest rates of in situ diversification, which led to it being an important source of species dispersing to other regions. All regional biotic interchanges were associated with documented hydrogeographic events and the formation of biogeographic corridors, including the Early Miocene (c. 23 to 16 Ma) uplift of the Serra do Mar and Serra da Mantiqueira and the Late Miocene (c. 10 Ma) uplift of the Northern Andes and associated formation of the modern transcontinental Amazon River. The combination of high diversification rates and extensive biotic interchange associated with Western Amazonia yielded its extraordinary contemporary richness and phylogenetic endemism. Our results support the hypothesis that landscape dynamics, which shaped the history of drainage basin connections, strongly affected the assembly and diversification of basin-wide fish faunas.

Coupling environment and physiology to predict effects of climate change on the taxonomic and functional diversity of fish assemblages in the Murray-Darling Basin, Australia.

This study uses species distribution modeling and physiological and functional traits to predict the impacts of climate change on native freshwater fish in the Murray-Darling Basin, Australia. We modelled future changes in taxonomic and functional diversity in 2050 and 2080 for two scenarios of carbon emissions, identifying areas of great interest for conservation. Climatic-environmental variables were used to model the range of 23 species of native fish under each scenario. The consensus model, followed by the physiological filter of lethal temperature was retained for interpretation. Our study predicts a severe negative impact of climate change on both taxonomic and functional components of ichthyofauna of the Murray-Darling Basin. There was a predicted marked contraction of species ranges under both scenarios. The predictions showed loss of climatically suitable areas, species and functional characters. There was a decrease in areas with high values of functional richness, dispersion and uniqueness. Some traits are predicted to be extirpated, especially in the most pessimistic scenario. The climatic refuges for fish fauna are predicted to be in the southern portion of the basin, in the upper Murray catchment. Incorporating future predictions about the distribution of ichthyofauna in conservation management planning will enhance resilience to climate change.

Modeling the ecology and evolution of biodiversity: Biogeographical cradles, museums, and graves.

Individual processes shaping geographical patterns of biodiversity are increasingly understood, but their complex interactions on broad spatial and temporal scales remain beyond the reach of analytical models and traditional experiments. To meet this challenge, we built a spatially explicit, mechanistic simulation model implementing adaptation, range shifts, fragmentation, speciation, dispersal, competition, and extinction, driven by modeled climates of the past 800,000 years in South America. Experimental topographic smoothing confirmed the impact of climate heterogeneity on diversification. The simulations identified regions and episodes of speciation (cradles), persistence (museums), and extinction (graves). Although the simulations had no target pattern and were not parameterized with empirical data, emerging richness maps closely resembled contemporary maps for major taxa, confirming powerful roles for evolution and diversification driven by topography and climate.

Two sides of a coin: Effects of climate change on the native and non-native distribution of Colossoma macropomum in South America.

Climate change and species invasions interact in nature, disrupting biological communities. Based on this knowledge, we simultaneously assessed the effects of climate change on the native distribution of the Amazonian fish Colossoma macropomum as well as on its invasiveness across river basins of South America, using ecological niche modeling. We used six niche models within the ensemble forecast context to predict the geographical distribution of C. macropomum for the present time, 2050 and 2080. Given that this species has been continuously introduced into non-native South American basins by fish farming activities, we added the locations of C. macropomum farms into the modeling process to obtain a more realistic scenario of its invasive potential. Based on modelling outputs we mapped climate refuge areas at different times. Our results showed that a plenty of climatically suitable areas for the occurrence of C. macropomum occurrence are located outside the original basins at the present time and that its invasive potential is greatly amplified by fish farms. Simulations of future geographic ranges revealed drastic range contraction in the native region, implying concerns not only with respect to the species conservation but also from a socio-economic perspective since the species is a cornerstone of artisanal and commercial fisheries in the Amazon. Although the invasive potential is projected to decrease in the face of climate change, climate refugia will concentrate in Paraná River, Southeast Atlantic and East Atlantic basins, putting intense, negative pressures on the native fish fauna these regions. Our findings show that short and long-term management actions are required for: i) the conservation of natural stocks of C. macropomum in the Amazon, and ii) protecting native fish fauna in the climate refuges of the invaded regions.

Diet and ecomorphological relationships of four cichlid species from the Cuiabá River basin

Relationship between diet and morphology of cichlid were analyzed considering that the trophic apparatus determines differential food use among species. Cichlasoma dimerus and Satanoperca pappaterra showed a generalist diet, while Chaetobranchopsis australis and Crenicichla vittata consumed zooplankton and fish, respectively. Significant correlation between morphology and diet was not found, but C. australis differed from the others species in the upper mouth and longer gill rakers. The morphology data and food size segregated the cichlids into three groups. The first was comprised by C. australis, which has many and longer gill rakers and a more protractile mouth, the second by C. vittata, which have a larger and more-protruded mouth and the third by S. pappaterra and C. dimerus, with a smaller and lower mouth. The latter two groups have more widely spaced gill rakers and consumed larger food. Overall, our results showed different patterns of species grouping when considering morphological or diet data. However, to C. australis the gill rakers determine both the type and size of food.(AU)

A relação entre dieta e morfologia de ciclídeos foi analisada considerando que o aparato trófico determina o uso diferencial dos recursos alimentares entre as espécies. Cichlasoma dimerus e Satanoperca pappaterra, apresentaram dieta generalista, enquanto Chaetobranchopsis australis e Crenicichla vittata, consumiram zooplâncton e peixes, respectivamente. Nenhuma correlação significativa foi encontrada entre a morfologia e a dieta, entretanto, C. australis se distanciou das demais espécies, por apresentar boca superior e rastros branquiais longos e numerosos. Os dados de morfologia e tamanho do alimento consumido segregaram os ciclídeos em três grupos. O primeiro foi composto por C. australis , que possui rastros branquiais longos e numerosos, além de maior protractibilidade da boca, o segundo por C. vittata , que tem maior amplitude e protrusão da boca e o terceiro por S. pappaterra e C. dimerus que possuem boca pequena e inferior. Os dois últimos grupos apresentaram ainda, maior distância entre os rastros e consumiram alimentos maiores. Nossos resultados mostraram que, quando somente os dados morfológicos são considerados, as espécies foram agrupadas de forma diferente do que quando apenas os dados de dieta foram considerados. Entretanto, para C. australis os rastros branquiais determinam o tipo e tamanho do alimento.(AU)

Diet and ecomorphological relationships of four cichlid species from the Cuiabá River basin

Relationship between diet and morphology of cichlid were analyzed considering that the trophic apparatus determines differential food use among species. Cichlasoma dimerus and Satanoperca pappaterra showed a generalist diet, while Chaetobranchopsis australis and Crenicichla vittata consumed zooplankton and fish, respectively. Significant correlation between morphology and diet was not found, but C. australis differed from the others species in the upper mouth and longer gill rakers. The morphology data and food size segregated the cichlids into three groups. The first was comprised by C. australis, which has many and longer gill rakers and a more protractile mouth, the second by C. vittata, which have a larger and more-protruded mouth and the third by S. pappaterra and C. dimerus, with a smaller and lower mouth. The latter two groups have more widely spaced gill rakers and consumed larger food. Overall, our results showed different patterns of species grouping when considering morphological or diet data. However, to C. australis the gill rakers determine both the type and size of food.(AU)

A relação entre dieta e morfologia de ciclídeos foi analisada considerando que o aparato trófico determina o uso diferencial dos recursos alimentares entre as espécies. Cichlasoma dimerus e Satanoperca pappaterra, apresentaram dieta generalista, enquanto Chaetobranchopsis australis e Crenicichla vittata, consumiram zooplâncton e peixes, respectivamente. Nenhuma correlação significativa foi encontrada entre a morfologia e a dieta, entretanto, C. australis se distanciou das demais espécies, por apresentar boca superior e rastros branquiais longos e numerosos. Os dados de morfologia e tamanho do alimento consumido segregaram os ciclídeos em três grupos. O primeiro foi composto por C. australis , que possui rastros branquiais longos e numerosos, além de maior protractibilidade da boca, o segundo por C. vittata , que tem maior amplitude e protrusão da boca e o terceiro por S. pappaterra e C. dimerus que possuem boca pequena e inferior. Os dois últimos grupos apresentaram ainda, maior distância entre os rastros e consumiram alimentos maiores. Nossos resultados mostraram que, quando somente os dados morfológicos são considerados, as espécies foram agrupadas de forma diferente do que quando apenas os dados de dieta foram considerados. Entretanto, para C. australis os rastros branquiais determinam o tipo e tamanho do alimento.(AU)

Potenciais efeitos das mudanças climáticas futuras sobre a distribuição de um anuro da Caatinga Rhinella granulosa (Anura, Bufonidae) / Potential effects of climate change on the distribution of a Caatinga's frog Rhinella granulosa (Anura, Bufonidae)

In this study, we used two types of species distribution modelling (correlative and mechanistic) in order to evaluate the effects of climate change on the geographic distribution of Rhinella granulosa (Spix, 1824), distributed in the Caatinga biome. We tested the prediction that amphibians distributed in warm weather will have their spatial distribution constrained by high temperatures in the future. Using the correlation approach, we observed that the potential distribution generated by Euclidian Distance showed more conservative areas (e.g. with a smaller distance from optimum niche) limiting it to the current distribution of the species (e.g. Caatinga), and to small areas in the Cerrado biome. The mechanistic approach showed a less conservative result, in which the habitat indicated as suitable for R. granulosa comprised a large extension of South America, encompassing a contiguous area. In general, we observed that the spatial distribution of R. granulosa would not be strongly affected by climate change, at least until 2080. Probably, this species has a tolerant physiology to high temperatures and shows adaptations that support dry and hot weather.(AU)

Neste estudo, usamos dois tipos de modelagem de distribuição de espécies (correlativo e mecanístico), com o objetivo de avaliar o efeito das mudanças climáticas sob a distribuição geográfica de Rhinella granulosa (Spix, 1824), espécie inserida principalmente no bioma Caatinga. Avaliamos a predição, levantada por outros autores, de que espécies de anfíbios distribuídos em climas quentes terão suas distribuições espaciais restringidas por aumento da temperatura considerando cenários futuros. Na abordagem correlativa, os resultados mostraram que as distribuições espaciais geradas pelo modelo de distância Euclidiana foram mais conservativas, ou seja, as áreas que apresentaram menor distância do nicho ótimo se restringiram às áreas de distribuição real da espécie (Caatinga) e às pequenas regiões que abrangem o bioma Cerrado. A abordagem mecanística apresentou resultados menos conservativos, onde o habitat indicado como adequado para R. granulosa está contido em grande parte da América do Sul, formando uma extensa área contínua. No geral, verificou-se que R. granulosa não sofrerá forte influência climática sobre sua distribuição geográfica no futuro, pelo menos até 2080, provavelmente por apresentar uma fisiologia extremamente tolerante às altas temperaturas e por possuir adaptações para suportar clima quente e seco.(AU)

Potenciais efeitos das mudanças climáticas futuras sobre a distribuição de um anuro da Caatinga Rhinella granulosa (Anura, Bufonidae) / Potential effects of climate change on the distribution of a Caatinga's frog Rhinella granulosa (Anura, Bufonidae)

In this study, we used two types of species distribution modelling (correlative and mechanistic) in order to evaluate the effects of climate change on the geographic distribution of Rhinella granulosa (Spix, 1824), distributed in the Caatinga biome. We tested the prediction that amphibians distributed in warm weather will have their spatial distribution constrained by high temperatures in the future. Using the correlation approach, we observed that the potential distribution generated by Euclidian Distance showed more conservative areas (e.g. with a smaller distance from optimum niche) limiting it to the current distribution of the species (e.g. Caatinga), and to small areas in the Cerrado biome. The mechanistic approach showed a less conservative result, in which the habitat indicated as suitable for R. granulosa comprised a large extension of South America, encompassing a contiguous area. In general, we observed that the spatial distribution of R. granulosa would not be strongly affected by climate change, at least until 2080. Probably, this species has a tolerant physiology to high temperatures and shows adaptations that support dry and hot weather.

Neste estudo, usamos dois tipos de modelagem de distribuição de espécies (correlativo e mecanístico), com o objetivo de avaliar o efeito das mudanças climáticas sob a distribuição geográfica de Rhinella granulosa (Spix, 1824), espécie inserida principalmente no bioma Caatinga. Avaliamos a predição, levantada por outros autores, de que espécies de anfíbios distribuídos em climas quentes terão suas distribuições espaciais restringidas por aumento da temperatura considerando cenários futuros. Na abordagem correlativa, os resultados mostraram que as distribuições espaciais geradas pelo modelo de distância Euclidiana foram mais conservativas, ou seja, as áreas que apresentaram menor distância do nicho ótimo se restringiram às áreas de distribuição real da espécie (Caatinga) e às pequenas regiões que abrangem o bioma Cerrado. A abordagem mecanística apresentou resultados menos conservativos, onde o habitat indicado como adequado para R. granulosa está contido em grande parte da América do Sul, formando uma extensa área contínua. No geral, verificou-se que R. granulosa não sofrerá forte influência climática sobre sua distribuição geográfica no futuro, pelo menos até 2080, provavelmente por apresentar uma fisiologia extremamente tolerante às altas temperaturas e por possuir adaptações para suportar clima quente e seco.

Metabolic Theory of Ecology and diversity of continental zooplankton in Brazil / A Teoria Metabólica da Ecologia e a diversidade do zooplâncton continental no Brasil

Several ecological hypotheses try to explain geographical patterns in biodiversity. The Metabolic Theory of Ecology (MTE) predicts that temperature is the main determinant of richness patterns for ectothermic organisms and that the relationship between richness (lnS) and temperature (1/kT) is a linear relationship with angular coefficient (b) near -0.65. This study tested the MTE for continental zooplankton diversity in 63 lakes in Brazil. Copepoda, Cladocera and Rotifera, as well as the three groups combined, showed different patterns from that predicted by MTE, with b values equal to 0.871, 0.516, 0.720 and 0.901, respectively. Temperature explains 12.7% of the richness of Copepoda, 5.3% of Cladocera, 6.7% of Rotifera, and 11.4% of all zooplankton groups together. Several studies have shown that the MTE does not apply to many terrestrial groups, perhaps because the model does not consider variances generated by other factors such as environmental spatial range, body size and other variables. The present study confirms this point of view, expanding it to continental aquatic invertebrates as well.

Várias hipóteses ecológicas tentam explicar os padrões geográficos de biodiversidade. A Teoria Metabólica da Ecologia (Metabolic Theory of Ecology - MTE) prediz que a temperatura é o principal determinante dos padrões de riqueza de organismos ectotérmicos e que a relação entre riqueza (lnS) e temperatura (1/kT) é uma reta com coeficiente angular (b) próximo a -0,65. O presente estudo testou a MTE para a diversidade zooplanctônica continental em 63 lagos brasileiros. Copepoda, Cladocera e Rotifera, assim como os três grupos analisados em conjunto, apresentaram padrões diferentes do previsto pela MTE, com os valores de b iguais a 0,871; 0,516; 0,720 e 0,901, respectivamente. A temperatura explicou 12,7% da riqueza de Copepoda, 5,3% de Cladocera, 6,7% de Rotifera e 11,4% do zooplâncton total. Diversos trabalhos têm demonstrado que a MTE não se aplica a muitos grupos terrestres, talvez porque o modelo não prevê desvios ocasionados por fatores como a variação espacial no ambiente, o tamanho corporal e outras variáveis. O presente trabalho corrobora este ponto de vista, expandindo-o também para invertebrados aquáticos continentais.

Metabolic Theory of Ecology and diversity of continental zooplankton in Brazil - doi: 10.4025/actascibiolsci.v34i1.9087

Several ecological hypotheses try to explain geographical patterns in biodiversity. The Metabolic Theory of Ecology (MTE) predicts that temperature is the main determinant of richness patterns for ectothermic organisms and that the relationship between richness (lnS) and temperature (1/kT) is a linear relationship with angular coefficient (b) near -0.65. This study tested the MTE for continental zooplankton diversity in 63 lakes in Brazil. Copepoda, Cladocera and Rotifera, as well as the three groups combined, showed different patterns from that predicted by MTE, with b values equal to 0.871, 0.516, 0.720 and 0.901, respectively. Temperature explains 12.7% of the richness of Copepoda, 5.3% of Cladocera, 6.7% of Rotifera, and 11.4% of all zooplankton groups together. Several studies have shown that the MTE does not apply to many terrestrial groups, perhaps because the model does not consider variances generated by other factors such as environmental spatial range, body size and other variables. The present study confirms this point of view, expanding it to continental aquatic invertebrates as well. macroecology; biodiversity; Copepoda; Cladocera; Rotífera; temperature gradients

Metabolic Theory of Ecology and diversity of continental zooplankton in Brazil - doi: 10.4025/actascibiolsci.v34i1.9087

Several ecological hypotheses try to explain geographical patterns in biodiversity. The Metabolic Theory of Ecology (MTE) predicts that temperature is the main determinant of richness patterns for ectothermic organisms and that the relationship between richness (lnS) and temperature (1/kT) is a linear relationship with angular coefficient (b) near -0.65. This study tested the MTE for continental zooplankton diversity in 63 lakes in Brazil. Copepoda, Cladocera and Rotifera, as well as the three groups combined, showed different patterns from that predicted by MTE, with b values equal to 0.871, 0.516, 0.720 and 0.901, respectively. Temperature explains 12.7% of the richness of Copepoda, 5.3% of Cladocera, 6.7% of Rotifera, and 11.4% of all zooplankton groups together. Several studies have shown that the MTE does not apply to many terrestrial groups, perhaps because the model does not consider variances generated by other factors such as environmental spatial range, body size and other variables. The present study confirms this point of view, expanding it to continental aquatic invertebrates as well. macroecology; biodiversity; Copepoda; Cladocera; Rotífera; temperature gradients

Deviations from predictions of the metabolic theory of ecology can be explained by violations of assumptions.

The metabolic theory of ecology (MTE) is based on models derived from the first principles of thermodynamics and biochemical kinetics. The MTE predicts that the relationship between temperature and species richness of ectotherms should show a specific slope. Testing the validity of this model, however, depends on whether empirical data do not violate assumptions and are obtained within contour conditions. When dealing with richness gradients, the MTE must be empirically tested only for ectothermic organisms at high organization levels and when their body size as well as abundance does not vary with temperature gradients. Here we evaluate whether the magnitude of the deviations in slope expected from the MTE to empirical data for New World amphibians is due to the violations of model assumptions and to lack of generality due to restricting contour conditions. We found that the MTE correctly predicted biodiversity patterns only at higher levels of organization and when assumptions of the basic model were not violated. Approximately 60% of the deviations from the MTE-predicted slope across amphibian families were due to violations of the model assumptions. The hypothesis that richness patterns are a function of environmental temperature is too restrictive and does not take complex environmental and ecological processes into account. However, our results suggest that it may be possible to obtain multiple derivations of the MTE equation if idiosyncrasies in spatial and biological/ecological issues that are essential to understanding biodiversity patterns are considered.

Fishfauna trophic structure across longitudinal gradient of Salto Caxias Reservoir (Iguaçu River state of Paraná Brazil) in the third year after dam - DOI: 10.4025/actascibiolsci.v27i1.1362 / Estrutura trófica da ictiofauna, ao longo do gradiente longitudinal do reservatório de Salto Caxias (rio Iguaçu, Paraná, Brasil), no terceiro ano após o represamento - DOI: 10.4025/actascibiolsci.v27i1.1362

This study aims at evaluating the fishfauna trophic structure across the longitudinal gradient of Salto Caxias reservoir, in the third year after its dam (post 3). The data obtained were compared with the previous ones (pre and post 1) to verify if the species that altered their diets in the initial phase of the dam, returned to the same food resources offered by natural environment. S(tomachal) contents of 1527 fishes were analyzed, using the volumetric method. In general, fishes presented a great diversity of food items in their diets, usually with a predominant resource kind. Thus, the fishfauna was synthetized in eight trophic guilds. The detrivore and piscivore species did not alter their feeding habit across spatial gradient considerably). (A montanteUpstream, all the trophic guilds were equally distributed compared to the other sites. Comparing pre and post 1 periods with the post 3 results showed that few species returned to their original trophic habit

Objetivou-se, neste estudo, avaliar a estrutura trófica da ictiofauna, ao longo do gradiente longitudinal do reservatório de Salto Caxias, no terceiro ano após seu represamento (pós 3). Compararam-se os dados obtidos neste trabalho com dados anteriores (pré e pós 1), a fim de verificar se as espécies que alteraram suas dietas no início do represamento voltaram a utilizar os mesmos recursos alimentares oferecidos no ambiente natural. Foram analisados conteúdos estomacais de 1527 exemplares pelo método volumétrico. A maioria das espécies apresentou dietas compostas por grande diversidade de itens alimentares, predominando, geralmente, um tipo de recurso. A ictiofauna foi organizada em oito guildas tróficas. As espécies detritívoras e piscívoras não alteraram consideravelmente seu hábito alimentar ao longo do gradiente espacial. A montante, todas as guildas estiveram distribuídas em proporção mais semelhante do que nos demais locais. Comparando-se os períodos de pré e pós 1 com o pós 3, verifica-se que poucas espécies retomaram seu hábito alimentar original

Fishfauna trophic structure across longitudinal gradient of Salto Caxias Reservoir (Iguaçu River state of Paraná Brazil) in the third year after dam - DOI: 10.4025/actascibiolsci.v27i1.1362 / Estrutura trófica da ictiofauna, ao longo do gradiente longitudinal do reservatório de Salto Caxias (rio Iguaçu, Paraná, Brasil), no terceiro ano após o represamento - DOI: 10.4025/actascibiolsci.v27i1.1362

This study aims at evaluating the fishfauna trophic structure across the longitudinal gradient of Salto Caxias reservoir, in the third year after its dam (post 3). The data obtained were compared with the previous ones (pre and post 1) to verify if the species that altered their diets in the initial phase of the dam, returned to the same food resources offered by natural environment. S(tomachal) contents of 1527 fishes were analyzed, using the volumetric method. In general, fishes presented a great diversity of food items in their diets, usually with a predominant resource kind. Thus, the fishfauna was synthetized in eight trophic guilds. The detrivore and piscivore species did not alter their feeding habit across spatial gradient considerably). (A montanteUpstream, all the trophic guilds were equally distributed compared to the other sites. Comparing pre and post 1 periods with the post 3 results showed that few species returned to their original trophic habit

Objetivou-se, neste estudo, avaliar a estrutura trófica da ictiofauna, ao longo do gradiente longitudinal do reservatório de Salto Caxias, no terceiro ano após seu represamento (pós 3). Compararam-se os dados obtidos neste trabalho com dados anteriores (pré e pós 1), a fim de verificar se as espécies que alteraram suas dietas no início do represamento voltaram a utilizar os mesmos recursos alimentares oferecidos no ambiente natural. Foram analisados conteúdos estomacais de 1527 exemplares pelo método volumétrico. A maioria das espécies apresentou dietas compostas por grande diversidade de itens alimentares, predominando, geralmente, um tipo de recurso. A ictiofauna foi organizada em oito guildas tróficas. As espécies detritívoras e piscívoras não alteraram consideravelmente seu hábito alimentar ao longo do gradiente espacial. A montante, todas as guildas estiveram distribuídas em proporção mais semelhante do que nos demais locais. Comparando-se os períodos de pré e pós 1 com o pós 3, verifica-se que poucas espécies retomaram seu hábito alimentar original

Diet and trophic ecomorphology of the silverside, Odontesthes bonariensis, of the Salto Caxias reservoir, rio Iguaçu, Paraná, Brazil

This study aims to analyze the diet and trophic ecomorphology of Odontesthes bonariensis, relating these features with species' abundance in the natural environment and in the Salto Caxias reservoir (at Iguaçu river) after the reservoir's formation. The samples were carried out before (from March 1997 to February 1998- pre) and after (from October 1998 to February 2001 - post 1 and 2) the damming. The stomach contents of 218 individuals were analyzed by occurrence and volumetric methods. O. bonariensis' diet is based on insects, scales, plants and detritus. Microcrustaceans (Cladocera and Copepoda) were the main items, allowing the characterization of the species as zooplanktivore. The species has a superior position and protractible mouth, with small teeth, creating a serrated pattern, uniformly lined side by side. There are many gill rakers, that are long and close together (typical of filtering fishes); the stomach is ill defined and the intestine is short. There was a gradual increase of O. bonariensis' abundance during the period of field study, mainly after the second year of damming. This fact seems to be closely related with the high abundance and availability of zooplankton in the dammed environment, and also with the ability of the species to exploit this resource.

Este estudo teve como objetivo analisar a dieta e ecomorfologia trófica de Odontesthes bonariensis, relacionando estes aspectos à abundância da espécie, no ambiente natural e após a formação do reservatório de Salto Caxias, Rio Iguaçu. As coletas foram realizadas antes (de março de 1997 a fevereiro de 1998 - pré-represamento) e após o represamento (de outubro de 1998 a fevereiro de 2001- pós 1 e 2) e os conteúdos estomacais de 218 exemplares foram analisados pelos métodos de ocorrência e volumétrico. A dieta baseou-se em insetos, escamas, vegetais e detritos, sendo que microcrustáceos (Cladocera e Copepoda) foram dominantes, permitindo caracterizar a espécie como zooplanctívora. A espécie possui boca superior e protátil com dentes pequenos, dispostos em fileiras, conferindo-lhes um aspecto serrilhado. Os rastros branquiais são numerosos, longos e próximos entre si (típico de peixe filtrador), o estômago é pouco definido e seu intestino curto. Houve um incremento gradativo na abundância de O. bonariensis, durante o período de coletas, principalmente no segundo ano após o represamento. Este fato parece estar estreitamente relacionado com a elevada abundância e disponibilidade de zooplâncton no ambiente represado e a capacidade da espécie em explorar este recurso.

Diet and trophic ecomorphology of the silverside, Odontesthes bonariensis, of the Salto Caxias reservoir, rio Iguaçu, Paraná, Brazil

This study aims to analyze the diet and trophic ecomorphology of Odontesthes bonariensis, relating these features with species' abundance in the natural environment and in the Salto Caxias reservoir (at Iguaçu river) after the reservoir's formation. The samples were carried out before (from March 1997 to February 1998- pre) and after (from October 1998 to February 2001 - post 1 and 2) the damming. The stomach contents of 218 individuals were analyzed by occurrence and volumetric methods. O. bonariensis' diet is based on insects, scales, plants and detritus. Microcrustaceans (Cladocera and Copepoda) were the main items, allowing the characterization of the species as zooplanktivore. The species has a superior position and protractible mouth, with small teeth, creating a serrated pattern, uniformly lined side by side. There are many gill rakers, that are long and close together (typical of filtering fishes); the stomach is ill defined and the intestine is short. There was a gradual increase of O. bonariensis' abundance during the period of field study, mainly after the second year of damming. This fact seems to be closely related with the high abundance and availability of zooplankton in the dammed environment, and also with the ability of the species to exploit this resource.

Este estudo teve como objetivo analisar a dieta e ecomorfologia trófica de Odontesthes bonariensis, relacionando estes aspectos à abundância da espécie, no ambiente natural e após a formação do reservatório de Salto Caxias, Rio Iguaçu. As coletas foram realizadas antes (de março de 1997 a fevereiro de 1998 - pré-represamento) e após o represamento (de outubro de 1998 a fevereiro de 2001- pós 1 e 2) e os conteúdos estomacais de 218 exemplares foram analisados pelos métodos de ocorrência e volumétrico. A dieta baseou-se em insetos, escamas, vegetais e detritos, sendo que microcrustáceos (Cladocera e Copepoda) foram dominantes, permitindo caracterizar a espécie como zooplanctívora. A espécie possui boca superior e protátil com dentes pequenos, dispostos em fileiras, conferindo-lhes um aspecto serrilhado. Os rastros branquiais são numerosos, longos e próximos entre si (típico de peixe filtrador), o estômago é pouco definido e seu intestino curto. Houve um incremento gradativo na abundância de O. bonariensis, durante o período de coletas, principalmente no segundo ano após o represamento. Este fato parece estar estreitamente relacionado com a elevada abundância e disponibilidade de zooplâncton no ambiente represado e a capacidade da espécie em explorar este recurso.

Astyanax altiparanae Garutti & Britski, 2000 (Osteichthyes, Tetragonopterinae) diet before and after the formation of Salto Caxias Reservoir, state of Paraná, Brazil / Avaliação da dieta de Astyanax altiparanae Garutti & Britski, 2000 (Osteichthyes, Tetragonopterinae) antes e após a formação do reservatório de Salto Caxias, Estado do Paraná, Brasil

Astyanax altiparanae (Osteichthyes, Tetragonopterinae) diet was evaluated before and after the Salto Caxias (Iguaçu river) dam closure, in order to investigate this species trophic adaptability. Samples were taken from March 1997 to February 2000, and the contents of 583 stomachs were analyzed, separated and volumetrically quantified. During the river phase, the species showed a tendency to herbivory and, during the reservoir phase, to omnivory. Group analysis (DCA) showed two distinct temporal groups: specimens with more specialized diet, collected in phase river, and specimens collected after dam closure, with mixed diet. The results suggest that A. altiparanae has high trophic adaptability and may succeed in the new environment.

Esse estudo objetivou avaliar a dieta de Astyanax altiparanae (Osteichthyes, Tetragonopterinae) no ambiente natural e após a formação do reservatório de Salto Caxias, rio Iguaçu, Estado do Paraná, Brasil, a fim de investigar a adaptabilidade trófica da espécie. As coletas foram realizadas de março/97 a fevereiro/00 resultando na obtenção de 582 estômagos, cujos itens alimentares foram quantificados, volumetricamente. Na fase rio, a espécie mostrou forte tendência à herbivoria, e após o represamento, uma dieta onívora. Na análise de agrupamento (DCA), formaram-se grupos temporais distintos: o primeiro agrupou alguns exemplares coletados na fase rio com dieta mais especializada e o segundo, exemplares coletados após o represamento e que apresentaram dieta mista. Os resultados evidenciaram que A. altiparanae mostrou alta adaptabilidade trófica, indicando que poderá ser bem sucedida no novo ambiente.

Astyanax altiparanae Garutti & Britski, 2000 (Osteichthyes, Tetragonopterinae) diet before and after the formation of Salto Caxias Reservoir, state of Paraná, Brazil / Avaliação da dieta de Astyanax altiparanae Garutti & Britski, 2000 (Osteichthyes, Tetragonopterinae) antes e após a formação do reservatório de Salto Caxias, Estado do Paraná, Brasil

Astyanax altiparanae (Osteichthyes, Tetragonopterinae) diet was evaluated before and after the Salto Caxias (Iguaçu river) dam closure, in order to investigate this species trophic adaptability. Samples were taken from March 1997 to February 2000, and the contents of 583 stomachs were analyzed, separated and volumetrically quantified. During the river phase, the species showed a tendency to herbivory and, during the reservoir phase, to omnivory. Group analysis (DCA) showed two distinct temporal groups: specimens with more specialized diet, collected in phase river, and specimens collected after dam closure, with mixed diet. The results suggest that A. altiparanae has high trophic adaptability and may succeed in the new environment.

Esse estudo objetivou avaliar a dieta de Astyanax altiparanae (Osteichthyes, Tetragonopterinae) no ambiente natural e após a formação do reservatório de Salto Caxias, rio Iguaçu, Estado do Paraná, Brasil, a fim de investigar a adaptabilidade trófica da espécie. As coletas foram realizadas de março/97 a fevereiro/00 resultando na obtenção de 582 estômagos, cujos itens alimentares foram quantificados, volumetricamente. Na fase rio, a espécie mostrou forte tendência à herbivoria, e após o represamento, uma dieta onívora. Na análise de agrupamento (DCA), formaram-se grupos temporais distintos: o primeiro agrupou alguns exemplares coletados na fase rio com dieta mais especializada e o segundo, exemplares coletados após o represamento e que apresentaram dieta mista. Os resultados evidenciaram que A. altiparanae mostrou alta adaptabilidade trófica, indicando que poderá ser bem sucedida no novo ambiente.