A new karyotype of Oligoryzomys (Sigmodontinae, Rodentia) from central Brazil

摘要

The genus Oligoryzomys Bangs, 1900 has a widespread distribution, from northern Central America to the southern part of South America. Fifteen species were recognized in the latest checklist of the genus, seven of which occurring in Brazil: O. chacoensis, O. delticola, O. eliurus, O. flavescens, O. fulvescens, O. microtis, and O. nigripes (Musser and Carleton 1993). These Oligoryzomys species occur in four Brazilian biomes: Cerrado, Caatinga, Atlantic Forest and Amazon. Recently, O. stramineus, an endemic species of the Brazilian Cerrado and Caatinga was described (Bonvicino and Weksler 1998) while O. fornesi Massoia, 1973 was recognized as a valid species (Myers et al. 1995; Bonvicino and Weksler 1998). These findings extended the number of Brazilian Oligoryzomys species to nine. However, previous studies based on morphologic similarities and G-band pattern suggested that O. nigripes was as senior synonymous of O. delticola and O. eliurus (Bonvicino and Weksler 1998).Oligoryzomys karyology, morphology, and geographic distribution have been reported in the last 25 years by many authors (Gardner and Patton 1976; Almeida and Yonenaga-Yassuda 1991; Espinosa and Reig 1991; Sbalqueiro et al. 1991; Bonvicino et al. 2001). Other inventories allow the identification of new species and karyotypes of Oligoryzomys in Brazil (Silva and Yonenaga-Yassuda 1997; Bonvicino and Weksler 1998). Due to the extreme similarity in morphological attributes among Oligoryzomys species, karyologic studies have been used to clarify the taxonomy of some species and understanding the diversification of the genus. The highest diploid number in the genus 2n=68, AN=74 or 76 was found in Peru (Gardner and Patton 1976) and the lowest diploid numbers, 2n=44, 44/45, AN=52, 52/53 in Brazil (Silva and Yonenaga-Yassuda 1997).In this paper, we describe a new Oligoryzomys karyotype, with the highest diploid number in the genus, comment on the geographic distribution and morphological characteristics of this karyomorph, herein referred to as Oligoryzomys sp., and compare our findings with karyologic data on related species.