Differentiation in the Atlantic Forest: phylogeography of Akodon montensis (Rodentia, Sigmodontinae) and the Carnaval--Moritz model of Pleistocene refugia.

According to the Carnaval--Moritz (CM) model of Pleistocene refugia, during the Last Glacial Maximum, forested areas of the Atlantic Forest (AF) were restricted to isolated refugia and later expanded to their current distribution. Phylogeographic patterns of several vertebrate species corroborated the existence of the so-called Pernambuco, Bahia, and São Paulo refugia in the central and northern AF. Here we shift focus to the neglected southern and interior AF by addressing the phylogeography of the mouse Akodon montensis as inferred through analysis of cytochrome-b gene sequences of 86 specimens collected at 36 localities in Argentina, Brazil, and Paraguay. Three main clades were recovered with average genetic divergence of 2.5%: a northern clade, differentiated in the Bahia refuge, a southern clade--for which we propose the Rio Grande do Sul refugium--and a central clade (widely extending from coastal Brazil to Argentina and Paraguay). Within the latter, genetic diversity and historical demographic estimations support differentiation in the São Paulo refugium and their later population expansion toward interior AF. Additionally, no riverine barrier effect was found associated with the main river in the interior AF, the Paraná River. Taken as a whole, the phylogeographic pattern of A. montensis and its recent population history are mainly concordant with the CM model. [ABSTRACT FROM AUTHOR]