Evolução molecular e cariotípica em Rhipidomys Tschudi, 1845 (Cricetidae, Rodentia)

• Autor(a) principal: Carvalho, Ana Heloisa de
• Data de Publicação: 2017
• Tipo de documento: Tese
• Idioma: por
• Título da fonte: Repositório Institucional da Universidade Federal do Espírito Santo (riUfes)
• Texto Completo: http://repositorio.ufes.br/handle/10/9925
• topic: Introgressão; Distribuição geográfica; Taxonomia; Espécie nova; Filogenia molecular; Marcador mitocondria; Marcador nuclear; Cariótipo; Rhipidomys cearanus; Introgression; Geographic distribution; Taxonomy; Molecular phylogeny; Mitochondrial marker; Nuclear marker; Karyotype; Zoologia; 57

Rhipidomys (Cricetidae, Rodentia) taxonomy is very complex, and the identification of specimens is usually based on continuous morphological characters. In previous phylogenetic studies, based in the Cytochrome B (Cytb) gene, among other lines of evidence, 12 of the 23 recognized species were sampled: three of them have been identified and described after these studies and another one is not formally described yet. These data indicate that the morphological variation may underestimate the diversity of the genus. Karyotype is usually a reliable taxonomic character for rodents but, concerning Rhipidomys, many have been described but not necessarily associated with a recognized species or misinterpreted. Karyotypes of specimens from different localities, that were identified on basis of molecular and/or morphological characters, were analyzed. We reviewed the karyotypic information available in literature for Rhipidomys and some were reinterpreted. This genus presents three karyological groups: a group presenting diploid number (2n) equal to 44, and low fundamental number (FN) varying from 48 to 52; a group presenting 2n=44, FN high, FN=72–80; and a group presenting 2n different from 44, 2n=48 and 50 and FN=66–72. Most species of this genus presents 2n=44 and low FN, all of these karyotypes being very similar. We assume that the ancestral karyotype of the genus should be similar to these, since are the ones recorded for Rhipidomys basal clades and are registered for specimens nearest to Central America, region of the cladogenesis event between Rhipidomys and Thomasomys probably occurs which presents some species showing 2n similar to 44, including 2n=44, and low FN. In addition to the 2n=44 and low FN karyotypes group, a single clade includes the other two groups: the group presenting 2n=48 e 50, which currently only includes R. nitela, but presented five distinct complements that can possibly comprise three taxonomic entities or distinctive populations; and a group with 2n=44 and high FN, that currently includes R. ipukensis and R. mastacalis. Molecular data, using two mitochondrial and four nuclear markers, associated with karyotype data, revealed two clades in R. mastacalis: one north of the Jequitinhonha river and another to the south. These clades correspond to two distinct species: R. mastacalis (2n=44, FN=74) and probably R. cearanus (2n=44, FN=72), a taxon name currently available but not current recognized. Within the clade characterized by high FN is R. emiliae that presents karyotype with 2n=44, FN=52, due to an introgression event confirmed by nuclear concatenated analysis. While karyotype analyzed by conventional staining does not distinguish well species with low FN, banding patterns suggest distinctions. We could not differentiate the main cause of variation in FN: centromeric repositioning or pericentric inversion. The explanation for the appearance of 2n=48 and 50 karyotype is more complex than a simple fission. In the present study the karyotype of Rhipidomys emiliae, R. ipukensis and R. tribei was described for the first time. Based on the molecular analysis, there is also the indication of possible new species.