Chromosome evolution on the genus Oligoryzomys (Cricetidae: Sigmodontinae): comparative studies by conventional cytogenetic and chromosome painting

Abstract

Rodentia is the most numerous order among mammals, comprising about 42% of mammalian species. Rodents are distributed in many types of environments and have specialized habits. The taxonomy of this group has been controversial mainly because of its remarkable diversity and high number of species. Example of this situation occurs in several genera of the tribe Oryzomyini, including Oligoryzomys, in which the number of species and phylogenetic relationships are controversial. Since the 1970's, cytogenetic studies in Neotropical rodents have increased considerably due to the emergence of differential staining techniques and utility of the karyotype as a tool for cytotaxonomy, especially for cryptic species. Several species of Oligoryzomys have been characterized by using such tools. Moreover, the genus presents high chromosomal variability - e.g. centric fusions, pericentric inversions, B chromosomes and polymorphic sex chromosomes - which evinces the importance of cytogenetic studies in this group. The aim of this project is to characterize cytogenetically the species of the genus Oligoryzomys, using conventional cytogenetic methods (CTG, GTG-banding and Ag-NORs staining) and karyotypic evolution through molecular cytogenetics studies with more refined techniques such as FISH with telomeric probes and reciprocal chromosome painting, which are informative for the detection and characterization of syntenic segments that have been maintained during the process of karyotypic differentiation. Furthermore, studies of molecular phylogeny, which have been developed for this group in our laboratory, will provide an important database for the elucidation of phylogenetic relationships of Oligoryzomys.