Genetic and morphological variability in South American rodent Oecomys (Sigmodontinae, Rodentia): evidence for a complex of species

Abstract

The rodent genus Oecomys (Sigmodontinae) comprises ~16 species that inhabit tropical and subtropical forests in Central America and South America. In this study specimens of Oecomys paricola Thomas, 1904 from Belém and Marajó island, northern Brazil, were investigated using cytogenetic, molecular and morphological analyses. Three karyotypes were found, two from Belém (2n = 68, fundamental number (FN) = 72 and 2n = 70, FN = 76) and a third from Marajó island (2n = 70, FN = 72). No molecular or morphological differences were found between the individuals with differing cytotypes from Belém, but differences were evident between the individuals from Belém and Marajó island. Specimens from Belém city region may represent two cryptic species because two different karyotypes are present in the absence of significant differences in morphology and molecular characteristics. The Marajó island and Belém populations may represent distinct species that have been separated for some time, and are in the process of morphological and molecular differentiation as a consequence of reproductive isolation at the geographic and chromosomal levels. Thus, the results suggest that O. paricola may be a complex of species.

Diversity and Karyotypic Evolution in the Genus <b><i>Neacomys </i></b>(Rodentia, Sigmodontinae)

“…1 ), it is also possible that our results indicate the beginning of a speciation process, since all over the Amazonian region large rivers are reproductive barriers for populations on opposite margins [Peres et al, 1996]. Similar results were found in the same region for Oecomys paricola [Rosa et al, 2012], where the populations of Marajó Island and Belém were inferred to be cryptic species.…”

“…The same happens in Taterillus (Rodentia, Gerbillinae) [Dobigny et al, 2002] and other genera of Sigmodontinae [Patton et al, 2000;Rosa et al, 2012].…”

“…This kind of event is frequently associated with polymorphisms of sex chromosomes in rodents [Paresque et al, 2007;Kasahara, 2009;Rosa et al, 2012]. Both morphologies of the Y (acrocentric and submetacentric) have heterochromatic blocks in the long arm, with the difference in morphology probably being a consequence of a pericentric inversion in the euchromatic region.…”

Oecomys catherinae (Sigmodontinae, Cricetidae): Evidence for chromosomal speciation?

“…This genus is distributed in almost all Brazilian territories, but there is some uncertainty about the geographic limitation of the species because there have been no collections in some areas/biomes [3]. The taxonomy of the genus is controversial [1, 4], mainly at the species level because of the existence of cryptic species and the overlap of morphological characters as observed in other rodents [5–7]. Also, the occurrence of cryptic species in tropical ecosystems has been suggested already [8].…”

“…It is possible that the same is occurring in the genus Oecomys , as already described for O . paricola [7]. …”