Abstract
The genus Oecomys (Rodentia, Sigmodontinae) is distributed from southern Central America to southeastern Brazil in South America. It currently comprises 18 species, but multidisciplinary approaches such as karyotypic, morphological and molecular studies have shown that there is a greater diversity within some lineages than others. In particular, it has been proposed that O. paricola constitutes a species complex with three evolutionary units, which have been called the northern, eastern and western clades. Aiming to clarify the taxonomic status of O. paricola and determine the relevant chromosomal rearrangements, we investigated the karyotypes of samples from eastern Amazonia by chromosomal banding and FISH with Hylaeamys megacephalus (HME) whole-chromosome probes. We detected three cytotypes for O. paricola: A (OPA-A; 2n = 72, FN = 75), B (OPA-B; 2n = 70, FN = 75) and C (OPA-C; 2n = 70, FN = 72). Comparative chromosome painting showed that fusions/fissions, translocations and pericentric inversions or centromeric repositioning were responsible for the karyotypic divergence. We also detected exclusive chromosomal signatures that can be used as phylogenetic markers. Our analysis of karyotypic and distribution information indicates that OPA-A, OPA-B and OPA-C are three distinct species that belong to the eastern clade, with sympatry occurring between two of them, and that the “paricola group” is more diverse than was previously thought.
Highlights
The arboreal genus Oecomys (Rodentia, Sigmodontinae) currently comprises 18 recognized species distributed from southern Central America to southeastern Brazil in South America, and is the most speciose genus of the Oryzomyini tribe
Chromosomal rearrangements could act as post-zygotic blockage of gene flow and play a leading role in the speciation process, potentially explaining the sympatry occurring between O. paricola: A (OPA-A) and O. paricola cytotype B (OPA-B), but in O. paricola cytotype C (OPA-C) the allopatric effect caused by the Tocantins River would relegate chromosomal rearrangements to a secondary role in the speciation process
Our results indicate that OPA-A, OPA-B and OPA-C are three distinct species that belong to the O. paricola eastern clade, with sympatry occurring between OPA-A and OPA-B
Summary
The arboreal genus Oecomys (Rodentia, Sigmodontinae) currently comprises 18 recognized species distributed from southern Central America to southeastern Brazil in South America, and is the most speciose genus of the Oryzomyini tribe. Desenvolvimento Cientıfico e Tecnologico (CNPq), www.cnpq.br The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript CYN ICAAF 007/2011 Fundacão Amazonia Paraense de Amparo à Pesquisa (FAPESPA), http://www. Br The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript JCP 2010/110447 Fundacão Amazonia Paraense de Amparo à Pesquisa (FAPESPA), http://www.fapespa.pa.gov. Uncertain, considering that morphological, phylogenetic (mtDNA and nuDNA), classic cytogenetics and chromosome painting analyses have shown that there is wide-ranging diversity within some lineages [1,2,3,4,5,6] These multidisciplinary approaches have helped researchers to comprehend better the distribution range and taxonomy of Oecomys, the resolution of O. bicolor, O. catherinae, O. cleberi, O. mamorae, O. paricola and O. roberti remains controversial.
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