ABSTRACT
The Atlantic Forest harbors a large species richness and high levels of endemism, but the processes that shaped its biodiversity are poorly studied, especially for mammals. Among them are the endemic mice Juliomys, which comprise forest dwellers distributed in southeastern and southern Brazil, northeastern Argentina, and eastern Paraguay. In this study, we investigate the phylogenetic relationships among species and perform phylogeographic analyses to evaluate the population structure and demographic scenarios through mitochondrial gene cytochrome b sequences. We investigate three hypotheses of diversification (forest refuges, montane isolate, and geomorphological events) to understand the evolution of the Juliomys species. Phylogenetic analyses recovered five clades/lineages, four of which are congruent with species currently recognized. The fifth lineage expands the range of the genus 659 km to the north and may represent a new species. The observed demographic and geographic structure of genetic diversity does not match the forest refuge hypothesis as mechanism to explain the diversification in Juliomys. Our results recovered J. rimofrons and J. ximenezi as sister species, supporting predictions of montane isolate hypothesis. We also detected a shallow genetic structure in J. pictipes and J. ossitenuis. Both phylogeographic breaks were congruent with limits of the São Paulo Basin, an area that has undergone Neogene reactivations of tectonic faults. It is suggested that geomorphological events led to a deformed landscape that influenced the dynamics of sedimentary basins and promoted an incipient population structure in J. pictipes and J. ossitenuis. Our findings demonstrate that the divergences whithin Juliomys species occurred during the Quaternary, too recently to have produced strong geographic structure.
ABSTRACT
The Atlantic Forest harbors a large species richness and high levels of endemism, but the processes that shaped its biodiversity are poorly studied, especially for mammals. Among them are the endemic mice Juliomys, which comprise forest dwellers distributed in southeastern and southern Brazil, northeastern Argentina, and eastern Paraguay. In this study, we investigate the phylogenetic relationships among species and perform phylogeographic analyses to evaluate the population structure and demographic scenarios through mitochondrial gene cytochrome b sequences. We investigate three hypotheses of diversification (forest refuges, montane isolate, and geomorphological events) to understand the evolution of the Juliomys species. Phylogenetic analyses recovered five clades/lineages, four of which are congruent with species currently recognized. The fifth lineage expands the range of the genus 659 km to the north and may represent a new species. The observed demographic and geographic structure of genetic diversity does not match the forest refuge hypothesis as mechanism to explain the diversification in Juliomys. Our results recovered J. rimofrons and J. ximenezi as sister species, supporting predictions of montane isolate hypothesis. We also detected a shallow genetic structure in J. pictipes and J. ossitenuis. Both phylogeographic breaks were congruent with limits of the São Paulo Basin, an area that has undergone Neogene reactivations of tectonic faults. It is suggested that geomorphological events led to a deformed landscape that influenced the dynamics of sedimentary basins and promoted an incipient population structure in J. pictipes and J. ossitenuis. Our findings demonstrate that the divergences whithin Juliomys species occurred during the Quaternary, too recently to have produced strong geographic structure.
ABSTRACT
Hylaeamys megacephalus (G. Fisher, 1814) presents great genetic diversity and wide geographical distribution, and occurs in both the Amazon and Cerrado biomes. Because of its generalist aspect, this species tolerates different eating habits and habitats. It occurs in flooded and dry areas and is predominantly terrestrial, which allows greater gene flow between populations even over long distances. Studies that seek a better understanding of morphological variations resulting from differences imposed by the environment throughout this species' distribution are still lacking. This study aimed to analyze the differences between H. megacephalus populations based on craniometry, investigating whether the environment has an influence on morphology. We analyzed a total of 142 specimens from three scientific mammal collections: National Museum, "Universidade Federal do Rio de Janeiro" (MN-UFRJ); "Laboratório de Biologia e Parasitologia de Mamíferos Reservatórios Silvestres", "Instituto Oswaldo Cruz", "Fundação Oswaldo Cruz"(LBCE-Fiocruz); and "Laboratório de Biodiversidade", "Universidade Federal de Goiás", "Regional Jataí" (LZE-UFG), and took 20 craniometric measurements. Craniometry was explored using unweighted pair group method with arithmetic mean (UPGMA), canonical variate analysis, and principal component analysis (PCA). The results led us to conclude that there are three craniometric groups of H. megacephalus with a tendency to differentiate as a result of geographical influences.(AU)
Com grande diversidade genética e distribuição geográfica, Hylaeamys megacephalus (G. Fisher, 1814) ocorre tanto na Amazônia quanto no Cerrado. Visto seu aspecto generalista, esta espécie tolera diversos hábitos alimentares e habitats, ocorrendo em áreas inundadas ou não, sendo predominantemente terrestre, permitindo maior fluxo de genes entre as populações, mesmo em longas distâncias. Apresenta ampla distribuição, e carece de estudos que busquem um melhor entendimento sobre as variações morfológicas resultantes das diferenças impostas pelo meio ao longo de sua distribuição. O estudo teve como objetivo, analisar as diferenças entre as populações de H. megacephalus, com base na craniometria investigando se o ambiente interfere na morfologia. Analisamos um total de 142 espécimes oriundos de coleções científicas de mamíferos, do Museu Nacional, Universidade Federal do Rio de Janeiro (MN-UFRJ), Laboratório de Biologia e Parasitologia de Mamíferos Reservatórios Silvestres, Instituto Oswaldo Cruz, Fundação Oswaldo Cruz (LBCE-Fiocruz) e Laboratório de Biodiversidade, Universidade Federal de Goiás, Regional Jataí, nos quais foram tomadas 20 medidas craniométricas. A craniometria foi explorada nas análises estatísticas de agrupamento de pares não ponderados com médias aritméticas (UPGMA), variação canônica e análise dos Componentes Principais (PCA). Os resultados encontrados nos levaram a concluir a existência de três grupos craniométricos da espécie de H. megacephalus com tendência a se diferenciarem, por influências geográficas.(AU)
