Diversidade morfológica e molecular do gênero Oecomys thomas, 1906 (Rodentia: Cricetidae) na Amazônia Oriental Brasileira

Abstract

The arboreal rice rats, genus Oecomys, are distributed in tropical and subtropical areas from Central and South America, with 17 currently recognized species and another two species already described in earlier studies but still unnamed. Six of these species are expected to occur in eastern Brazilian Amazon. Because defining the species limits inside Oecomys based only on morphological characters is a complicated task, many nominal taxa have already been associated to the genus, and different taxonomic arrangements have been proposed by specialists. Despite of this taxonomic instability, there is only one taxonomic review for the genus carried out 50 years ago, in which only two polytypical species were recognized. However, several recent studies based on morphological, molecular and karyotypical data have been showing that the species diversity inside Oecomys is largely underestimated, resulting in recent descriptions of new taxa or revalidation of previously synonymized species. This work aimed to assess the species diversity inside this genus in the eastern Brazilian Amazon by investigating the molecular and morphological variation in regional specimens. We employed phylogenetic analysis based on cytochrome-b in order to define clades that may represent species, and described the external and cranial morphology of these recognized species. As a result, we recognized 11 species in the eastern Amazonian forest in Brazil, of which five are already expected to occur in this area (Oecomys auyantepui, O. bicolor, O. paricola, O. rex, and O. rutilus), two are recorded for the first time in the biome Amazonia (Oecomys catherinae and O. cleberi), and the four are either new or not currently recognized species (i.e. synonyms), herein referred as Oecomys sp. A, Oecomys sp. B, Oecomys sp. C, and Oecomys sp. D. Moreover, we suggest that Oecomys bicolor is a species complex, based in the high nucleotide divergence we found (7.5 %), corroborating previous molecular studies. We observed sexual dimorphism and ontogenetic variation on cranial morphometry in the species Oecomys paricola, and for comparison purposes we treated all other species herein studied as exhibiting this kind of dimorphism. We also suggest a phylogenetic hypothesis among the species of this genus based on 653 bp of cytochrome-b. This is the most comprehensive phylogeny for Oecomys published to date, due to the great number of species included in the analysis (11 of the 16 currently recognized species plus seven probably new species), and the wide-ranging geographic area included in our sample.