Molecular systematics of Neotropical spiny mice (Neacomys: Sigmodontinae, Rodentia) from the Guianan Region

Abstract

Although three species of Neacomys (terrestrial spiny mice: Sigmodontinae) are currently recognized from the Guianan Region (northeastern South America), their taxonomic distinctness has not been tested with genetic data, their relationships to other congeneric forms is unknown, and there have been no studies of their intraspecific phylogeographic variation. These three species are very similar in their external morphology, and sympatry has been demonstrated for all three combinations of pairs. We have sequenced the cytochrome- b gene of 26 specimens morphologically identified as Neacomys paracou , Neacomys dubosti , and Neacomys guianae , for assessing their phylogenetic position with regard to other Amazonian taxa of the genus and for assessing their genetic variation within the Guianan Region. Our results (1) confirm that three genetically distinct species of Neacomys species occur in French Guiana, Suriname, and Guyana; (2) suggest that they are not closely related to one another vis-à-vis extralimital species; and (3) reveal shallow phylogeographic structure in only the most widespread form, N. paracou . The morphological examination of molecularly identified individuals of N . paracou and N. dubosti suggests that one external character, namely the relative size of caudal scales, is of dubious diagnostic value.