Padrões de variação genética e morfológica em Monodelphis de listras (Marsupialia: Didelphidae)
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2012-02-24
Autores
Cardoso, Rafaela Duda
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Universidade Federal do Espírito Santo
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Among Neotropical didelphid marsupials, Monodelphis americana, M. umbristriata, M. iheringi, M. scalops and M. theresa have three black dorsal stripes, and the description of the species was based on the presence and conspicuity of these features, beyond body size. However, some taxa are controversial about the identification and validity as species, due to small number of known specimens for some of them and observations about pelage variation mainly about the stripes. While morphological studies to date showed no conclusive results on these questions, there are few comparative molecular studies that include a comprehensive taxonomic and geographical sampling. The aims of this study was to investigate if intra and interspecific morphological and molecular variations of sympatric populations of M. americana and M. iheringi are recurrent, if the evolutionary patterns found (especially related to sexual dimorphism and ontogeny) repeat to other three-striped opossums, what is the adaptive function of the stripes and what are the systematic implications of this variation. We analyzed qualitative morphology of series of exemplars from all ages and both sexes, along the geographic distribution in Brazil, beyond phylogenetic analyses with cytochrome b sequences. For M. americana, we recovered 5 subclades, which have diagnostic morphotypes according to a latitudinal gradient of distribution. Among them, 4 subgroups are geographically limited by rivers and, yet, it was identified morphological variation linked to age and sex in 2 subclades, in overlapping areas with another striped opossum in the Southeast. Molecular and morphological data included M. umbristriata in 1 of these subclades, confirming synonymy with M. americana. Between M. scalops and M. theresa, the evaluation of all age phases, original descriptions and genetic information confirmed their synonymy and distribution limited to Southeast. For M. iheringi, both sexes are striped for whole life across its distribution, restricted to South and Southeast. Yet, the group of three-striped short-tailed opossums is not monophyletic, since M. scalops is not phylogenetically closest to M. americana and M. iheringi. So, the conspicuity of the stripes and their rarefaction are homoplasies, which causes morphological convergence among juveniles of the 3 species and pelage differentiation in males of M. americana and M. scalops during sexual maturation. Probably, perceptible stripes in juveniles assist in evading predators, while sexual selection drives the loss in sympatry to permit recognition from couple in relation to another taxon.
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CARDOSO, Rafaela Duda. Padrões de variação genética e morfológica em Monodelphis de listras (Marsupialia: Didelphidae). 2012. 80 f. Dissertação (Mestrado em Biologia Animal) - Universidade Federal do Espírito Santo, Centro de Ciências Humanas e Naturais, Vitória, 2012.