A new species of swamp rat of the genus Scapteromys Waterhouse, 1837 (Rodentia: Sigmodontinae) endemic to Araucaria angustifolia Forest in Southern Brazil

Abstract

A new species of swamp rat of the genus Scapteromys from the Meridional Plateau of Southern Brazil is described. Morphological, molecular, and karyological analysis support the recognition of the new species, distinct from S. aquaticus and S. tumidus. Scapteromys sp. nov. is significantly smaller than the congeneric taxa considering most of the external and craniometric measurements and the pelage is conspicuously grayer and darker. It can be distinguished from S. tumidus by the laterally extended thenar pad of the manus and the parallel edges of the hamular process of the pterygoid, and from S. aquaticus by a grayer and darker pelage and smaller values of most external and craniometric measurements. Karyological analysis indicated a difference in chromosome numbers across the distributional range: 2n=34 and 2n=36. A total of 11 haplotypes were found along the range of the new species within the biogeographic province of Araucaria angustifolia Forest. Strongly supported substructure was found within the new taxon, resulting in two reciprocally monophyletic clades.

Geographic variation in skull shape of the water rat Scapteromys tumidus (Cricetidae, Sigmodontinae): isolation-by-distance plus environmental and geographic barrier effects?

“…Since geographic distances limit dispersal, the rate of migration is higher between nearby populations than between distant populations (Wright 1943, Bradburd et al 2013). This pattern Quintela et al 2014). Such information, associated with an analysis of the present-day distribution of both species, leads to the hypothesis that the divergence between S. aquaticus and S. tumidus took place along the Lower Uruguay River basin and, according to Freitas et al (1984), S. tumidus is in the process of colonization eastward of the River Plate.…”

“…The genus Scapteromys comprises three recognized species of sigmodontine cricetid rodents, inhabitants of riverine and palustrine systems (Quintela et al 2014). Scapteromys aquaticus (Thomas, 1920) is a 2n=32 karyomorph (Brum-Zorrilla et al 1986) that extends from southern Paraguay to east-central Argentina, with individual records in Las Cañas, southeastern Uruguay, and São Borja, west of the state of Rio Grande do Sul, southern Brazil .…”

Diversidade de pequenos mamíferos (Didelphimorphia e Rodentia) do Holoceno do Nordeste do Estado do Rio Grande do Sul, Brasil: implicações taxonômicas e paleoambientais

“…Reig, 1987;Voss HADLER ET AL. -DIDELPHIMORPHIA E RODENTIA DO HOLOCENO DO RIO GRANDE DO SUL & Myers, 1991;Voss, 1993;Goin & Reye, 1997;Goin, 2001;Leite, 2003;Voss & Jansa, 2003;Weksler et al, 2006;Pardiñas et al, 2009;Pardiñas & Teta, 2011;Quintela et al, 2014). As medidas (em milímetros) foram obtidas com um paquímetro Mitutoyo com 0,02 mm de precisão.…”

Phylogenetic and morphological relationships between nonvolant small mammals reveal assembly processes at different spatial scales

“…We generated our own data for three species endemic to the study area: S. meridionalis , recently described (Quintela et al. ) and two undescribed taxa, Deltamys sp. and Oxymycterus sp.…”

“…In order to evaluate the evolutionary relationships among small mammal species and infer community assembly processes across several scales, we reconstructed a molecular phylogeny using 3.1 kb of multilocus DNA sequences, mostly using data previously available for specimens in public databases (e.g., GenBank). We generated our own data for three species endemic to the study area: S. meridionalis, recently described (Quintela et al 2014) and two undescribed taxa, Deltamys sp. and Oxymycterus sp.…”