Evolution and Systematics of the Atlantic Tree Rats, Genus Phyllomys (Rodentia, Echimyidae), With Description of Two New Species
The Atlantic tree rats, genus Phyllomys, are arboreal echimyids found in eastern Brazil. Species of Phyllomys are of conservation interest because they are poorly known, have restricted geographic ranges, and are endemic to the Atlantic forest, one of the most threatened ecosystems in the world. Here I examine the diversity of the genus Phyllomys using genetic and morphological data. The goals are to elucidate the taxonomy of the group, infer phylogenetic relationships among species, and understand the processes that led to the present diversity and distribution. The Atlantic tree rats have been referred to as Nelomys or grouped with the Amazonian genus Echimys. Given that Nelomys is a junior synonym of Echimys, the name Phyllomys should be used. Phyllomys is monophyletic and readily diagnosable by unique dental characters, and there is no reason to include it with Echimys. There are currently ten described and three ndescribed species of Phyllomys, two of which I describe here. Phylogenetic analyses of cytochrome b data corroborate the monophyly of the genus and indicate two geographically bounded clades: southern (P. dasythrix and P. aff. dasythrix) and northeastern (P. brasiliensis, P. lamarum, and P. blainvilii). The remaining species included in the analyses (P. pattoni, P. nigrispinus, and the two new species described here) are of uncertain placement. I address the tectonic, climatic, and vegetation changes in eastern Brazil since the Pliocene that set the stage for the diversification of Phyllomys and likely played a role in the phylogeographic patterns observed today.