One of the original goals of phylogeography was to use genetic data to identify historical events that might contribute to breaks among biotic communities. In this study, we examine the phylogeography of a common livebearing fish (Poecilia gillii) from Costa Rica. Our goal was to see if phylogeographic breaks in this species were congruent with previously-defined boundaries among four fish community provinces. We hypothesized that if abiotic factors influence both community boundaries and genetic structuring in P. gillii then we would find four monophyletic clades within our focal species that were geographically separated along community boundary lines. Similarly, we expected to find most of the genetic variation in P. gillii partitioned among these four geographic regions. We generated DNA sequence data (mitochondrial cyt b and nuclear S7 small ribosomal subunit) for 260 individuals from 42 populations distributed across Costa Rica. We analyzed these data using phylogenetic (parsimony and likelihood) and coalescent approaches to estimate phylogenetic relationships among haplotypes, patterns of gene flow, and effective population size. Contrary to our expectations, we did not find four monophyletic groups that mapped cleanly to our geographic community provinces. However, one of our clades was restricted to a single province, suggesting that common earth history events could be responsible for both genetic structuring in P. gillii and fish community composition in this area. However, our results show a complex pattern of gene flow throughout other regions in Costa Rica where genetic structuring is not governed by community province boundaries.

Antisymmetry is a striking, yet puzzling form of biological asymmetry. The livebearing fish Xenophallus umbratilis exhibits antisymmetry in the male intromittent organ and provides a system that is well-suited for studying the nature of variation in antisymmetrical traits. Using geometric morphometrics, I test the hypothesis that because the gonopodium is critical to fitness there will not be significant differences in gonopodium shape between the two gonopodial morphs in this species. My results are consistent with this prediction, though I found that gonopodium shape did differ with gonopodium size.

Thesis (Ph. D.)--University of California, Riverside, 2009. / Includes abstract. Available via ProQuest Digital Dissertations. Title from first page of PDF file (viewed March 17, 2010). Includes bibliographical references. Also issued in print.

Cytogenetic analysis using C-banding, silver staining and fluorescent staining was carried out on a population sample of Poecilia Iatipinna derived from Tampico, Mexico, to verify the presence of sex chromosomes in individuals from the southern areas of this species range and to investigate the extent of C-band and Ag-NOR polymorphisms. Females were found to have W heteromorphic chromosomes, with large amounts of heterochromatin-rich in AT nucleotide sequences. C-banding corresponded to the pattern proposed as typical for the genus. Specimens share one of the Ag- NOR locations previously described in populations from the U.S.A. and show additional ones as well.

A central question in life history theory is, what combination of traits and behaviors will lead to the highest reproductive success throughout a lifetime. The trade-off between current and future reproduction is central to the lifetime reproductive success of an organism. If there is a cost to reproduction, then allocation of energy to current reproduction will come at a cost to future reproduction. We expect young individuals to favor future reproduction over current reproduction and that balance shifts to current reproduction as they age (i.e. terminal investment hypothesis). However, how this transition from an emphasis on future reproduction to emphasis on current reproduction changes throughout a lifetime should depend on environmental factors like mortality and resource availability. We test for the generality of terminal investment across three species of poecilliid fishes in a range of environments. We found evidence of terminal investment in all three species in both high and low mortality environments and high and low resource availability environments. In general, high mortality or high resource availability tended to result in a decreased slope of the relationship between reproductive allocation and body size. Terminal investment appears to be general, even though there was an effect of high mortality and resource availability, it was not sufficient to completely preclude terminal investment.

No description available.

This thesis demonstrates how the intermittent nature of seasonal tropical fresh waters facilitates and impedes the dispersal of fish and how the variability among residual dry season pools affects the dynamics of isolated populations. I focused on the seasonal ecology of Poecilia gillii from pools in a steep gradient, intermittent stream in Costa Rica. Water temperature and dissolved oxygen concentration were affected by season, by between-pool differences, and by the interaction between seasonal and spatial influences. Seasonal flooding resulted in a catastrophic loss of fish from most pools. Population loss was influenced by the susceptibility of the pools to flooding and population density, with mortality occurring primarily in nearby desiccating "graveyard" pools. Pools increased in population size and density over the 5-month post-flood study period, and their densities converged to their pre-flood values. Variability in the rate of increase among pools was related to water quality and population density. Striking changes in the size and abundance of males over the season suggest social influences on maturation in Poecilia gillii.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Life-history theory is an important tool to understand differences in reproductive strategies among populations under different environmental conditions, and for the inference of possible local adaptations. Poeciliids are ideal organisms for the study of life-history divergence among populations due to their reproductive peculiarities based on different levels of viviparity, prompt responses to environmental conditions, continuous reproduction and a short generation time. Considering that Phalloceros harpagos, Poecilia reticulata and Poecilia vivipara - three poeciliid species found in the Ubatiba river, in Maricá municipality, Rio de Janeiro - have low-mobility populations and share similar diets, competition for food resources can greatly influence the life-history of these species in areas where they co-occur. Samples were collected at six locations of the Ubatiba river, which were selected by the pattern of poeciliid species occurrence. To compare the life histories of the three species we analyzed standard length, size at first maturity, total weight, gonadosomatic index (GSI), brood size, and the presence or absence of superfetation. In order to assess the changes in life history characteristics of each species according to location, data was separated by species, and then locations were compared. Besides the mentioned features, the presence or absence of matrotrophy was also examined. Correlation analysis showed that female size influences the total weight, reproductive investment and brood size of poeciliid species. Pregnant females of P. vivipara showed the highest standard length, size at first maturity, total weight, brood size and GSI among the three species. Life-history traits of P. reticulata exhibited similarities with either P. harpagos (standard length, size at first maturity and total weight) or P. vivipara (GSI). Brood size differed significantly among species. Between 12-15% of pregnant females of the three poeciliid species presented superfetation. P. harpagos life-history traits according to location showed that standard length, weight, GSI and brood size of females are closely related to the occurrence of other poeciliids. P. vivipara females also showed variations of GSI and brood size linked to co-occurrence, however, showed no differences in standard length and weight according to location. Whilst, P. reticulata presented differences in weight, GSI and brood size related to the occurrence of other species but not in length. We observed, for the three species, the concomitant presence of superfetation and matrotrophy, and there was evidence that the variation in degrees of matrotrophy was influenced by different patterns of occurrence. Poeciliids presented a variety of life-history patterns, which seem to have been shaped primarily by interspecific competition for food resources. / A teoria da história de vida é uma importante ferramenta para entender diferenças nas estratégias reprodutivas entre populações sob diferentes condições ambientais e para a inferência das possíveis adaptações locais. Os poecilídeos são excelentes modelos para estudos sobre a divergência da história de vida entre populações devido às suas peculiaridades reprodutivas baseadas em diferentes graus de viviparidade, respostas rápidas às condições ambientais, reprodução continuada e curto tempo de geração. Considerando que Phalloceros harpagos, Poecilia vivipara e Poecilia reticulata - três espécies de poecilídeos encontrados no rio Ubatiba, no município de Maricá, Rio de Janeiro - apresentam populações pouco móveis e compartilham dietas semelhantes, a competição por recursos alimentares pode influenciar bastante a história de vida dessas espécies em áreas onde as mesmas coocorrem. As coletas foram realizadas em seis localidades do rio Ubatiba, as quais foram selecionadas pelo padrão de ocorrência das espécies de poecilídeos. Para comparação das histórias de vida das três espécies, foram analisados o comprimento padrão, o tamanho da primeira maturação, o peso total, o índice gonadossomático (IGS), o tamanho da ninhada, e a presença ou ausência de superfetação. Com intuito de aferir as adaptações nas características da história de vida de cada espécie de acordo com a localidade, foram separados os dados das espécies, e então, comparadas as localidades. Além das características citadas, analisou-se também a presença ou ausência de matrotrofia. As análises de correlação demonstraram que o tamanho da fêmea influencia o peso total, o investimento reprodutivo e o tamanho da ninhada das espécies estudadas. As fêmeas grávidas de P. vivipara apresentaram os maiores valores de comprimento padrão, tamanho da primeira maturação, peso total, IGS e tamanho das ninhadas, entre as três espécies. As características da história de vida de P. reticulata exibiram semelhanças ora com P. harpagos (comprimento padrão, tamanho da primeira maturação e peso total), ora com P. vivipara (IGS). O tamanho das ninhadas diferiu significativamente entre as espécies. A superfetação esteve presente entre 12-15% das fêmeas grávidas das três espécies de poecilídeos. A análise das características da história de vida de P. harpagos de acordo com a localidade mostrou que o tamanho, peso, IGS e tamanho da ninhada das fêmeas estão intimamente relacionados à ocorrência de outros poecilídeos. As fêmeas de P. vivipara também apresentaram variações de IGS e tamanho da ninhada ligadas à coocorrência, contudo, não mostraram diferenças de tamanho e peso de acordo com a localidade. Já P. reticulata apresentou diferença de peso, IGS e tamanho da ninhada em relação à ocorrência das outras espécies, mas de tamanho não. Observou-se, para as três espécies, a presença concomitante de superfetação e matrotrofia, e houve indícios de que a variação dos graus de matrotrofia foi influenciada pelos diferentes padrões de ocorrência. Os poecilídeos apresentaram uma variedade de padrões de história de vida, os quais parecem ter sido moldados principalmente pela competição interespecífica por recursos alimentares

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Life-history theory is an important tool to understand differences in reproductive strategies among populations under different environmental conditions, and for the inference of possible local adaptations. Poeciliids are ideal organisms for the study of life-history divergence among populations due to their reproductive peculiarities based on different levels of viviparity, prompt responses to environmental conditions, continuous reproduction and a short generation time. Considering that Phalloceros harpagos, Poecilia reticulata and Poecilia vivipara - three poeciliid species found in the Ubatiba river, in Maricá municipality, Rio de Janeiro - have low-mobility populations and share similar diets, competition for food resources can greatly influence the life-history of these species in areas where they co-occur. Samples were collected at six locations of the Ubatiba river, which were selected by the pattern of poeciliid species occurrence. To compare the life histories of the three species we analyzed standard length, size at first maturity, total weight, gonadosomatic index (GSI), brood size, and the presence or absence of superfetation. In order to assess the changes in life history characteristics of each species according to location, data was separated by species, and then locations were compared. Besides the mentioned features, the presence or absence of matrotrophy was also examined. Correlation analysis showed that female size influences the total weight, reproductive investment and brood size of poeciliid species. Pregnant females of P. vivipara showed the highest standard length, size at first maturity, total weight, brood size and GSI among the three species. Life-history traits of P. reticulata exhibited similarities with either P. harpagos (standard length, size at first maturity and total weight) or P. vivipara (GSI). Brood size differed significantly among species. Between 12-15% of pregnant females of the three poeciliid species presented superfetation. P. harpagos life-history traits according to location showed that standard length, weight, GSI and brood size of females are closely related to the occurrence of other poeciliids. P. vivipara females also showed variations of GSI and brood size linked to co-occurrence, however, showed no differences in standard length and weight according to location. Whilst, P. reticulata presented differences in weight, GSI and brood size related to the occurrence of other species but not in length. We observed, for the three species, the concomitant presence of superfetation and matrotrophy, and there was evidence that the variation in degrees of matrotrophy was influenced by different patterns of occurrence. Poeciliids presented a variety of life-history patterns, which seem to have been shaped primarily by interspecific competition for food resources. / A teoria da história de vida é uma importante ferramenta para entender diferenças nas estratégias reprodutivas entre populações sob diferentes condições ambientais e para a inferência das possíveis adaptações locais. Os poecilídeos são excelentes modelos para estudos sobre a divergência da história de vida entre populações devido às suas peculiaridades reprodutivas baseadas em diferentes graus de viviparidade, respostas rápidas às condições ambientais, reprodução continuada e curto tempo de geração. Considerando que Phalloceros harpagos, Poecilia vivipara e Poecilia reticulata - três espécies de poecilídeos encontrados no rio Ubatiba, no município de Maricá, Rio de Janeiro - apresentam populações pouco móveis e compartilham dietas semelhantes, a competição por recursos alimentares pode influenciar bastante a história de vida dessas espécies em áreas onde as mesmas coocorrem. As coletas foram realizadas em seis localidades do rio Ubatiba, as quais foram selecionadas pelo padrão de ocorrência das espécies de poecilídeos. Para comparação das histórias de vida das três espécies, foram analisados o comprimento padrão, o tamanho da primeira maturação, o peso total, o índice gonadossomático (IGS), o tamanho da ninhada, e a presença ou ausência de superfetação. Com intuito de aferir as adaptações nas características da história de vida de cada espécie de acordo com a localidade, foram separados os dados das espécies, e então, comparadas as localidades. Além das características citadas, analisou-se também a presença ou ausência de matrotrofia. As análises de correlação demonstraram que o tamanho da fêmea influencia o peso total, o investimento reprodutivo e o tamanho da ninhada das espécies estudadas. As fêmeas grávidas de P. vivipara apresentaram os maiores valores de comprimento padrão, tamanho da primeira maturação, peso total, IGS e tamanho das ninhadas, entre as três espécies. As características da história de vida de P. reticulata exibiram semelhanças ora com P. harpagos (comprimento padrão, tamanho da primeira maturação e peso total), ora com P. vivipara (IGS). O tamanho das ninhadas diferiu significativamente entre as espécies. A superfetação esteve presente entre 12-15% das fêmeas grávidas das três espécies de poecilídeos. A análise das características da história de vida de P. harpagos de acordo com a localidade mostrou que o tamanho, peso, IGS e tamanho da ninhada das fêmeas estão intimamente relacionados à ocorrência de outros poecilídeos. As fêmeas de P. vivipara também apresentaram variações de IGS e tamanho da ninhada ligadas à coocorrência, contudo, não mostraram diferenças de tamanho e peso de acordo com a localidade. Já P. reticulata apresentou diferença de peso, IGS e tamanho da ninhada em relação à ocorrência das outras espécies, mas de tamanho não. Observou-se, para as três espécies, a presença concomitante de superfetação e matrotrofia, e houve indícios de que a variação dos graus de matrotrofia foi influenciada pelos diferentes padrões de ocorrência. Os poecilídeos apresentaram uma variedade de padrões de história de vida, os quais parecem ter sido moldados principalmente pela competição interespecífica por recursos alimentares

Understanding why some species coexist and others do not remains one of the fundamental challenges of ecology. While several lines of evidence suggest that closely related species are unlikely to occupy the same habitat because of competitive exclusion, there are many cases where closely related species do co-occur. Research comparing sympatric and allopatric populations of co-occurring species provides a framework to understand the role of phenotypic diversification in species coexistence. In this study I focus on the livebearing fish Poeciliopsis baenschi and ask if differences in phenotypic traits among populations can be explained by the presence or absence of the congeneric species P. turneri. I focus on phenotypic divergence in life history traits and in body shape, two sets of integrated traits likely to respond to variation in competition. Additionally, I compare explore the effects of sympatry and allopatry on sexual dimorphism. I take advantage of a natural experiment in western Mexico where P. baenschi co-occur with P. turneri in some locations (sympatric populations) but also exist in isolation in other locations (allopatric populations). My results show that sympatric populations of P. baenschi differed significantly in life history traits and body shape when compared to their allopatric counterparts. Additionally, the amount of sexual dimorphism differed between sympatric and allopatric populations of P. baenschi, suggesting different constraints might exist in sympatry and allopatry for sexual dimorphism. Lastly, I explore my results in the context of trait evolution as it relates to species coexistence.