sábado, 20 de setembro de 2014

A new species of Leaf-eared Mouse, genus Phyllotis Waterhouse, 1837 (Rodentia: Cricetidae) from northern Peru

PACHECO, V.; RENGIFO, E.M.; VIVAS, D. 2014. A new species of Leaf-eared Mouse, genus Phyllotis Waterhouse, 1837 (Rodentia: Cricetidae) from northern Peru. THERYA 5(2):481-508. doi: 10.12933/therya-14-185

Introduction: Leaf-eared mice, Phyllotis comprise a highly species-rich genus distributed in the Andes of South America from sea level to 5,500 m. This genus includes 15 species in three groups: andium/amicus, osilae, and darwini groups (sensu Steppan et al. 2007). We describe a new species of rodent of the genus Phyllotis from the northern Peruvian Andes, which has been mentioned in the literature as Phyllotis sp. nov. 1 or Phyllotis sp. and placed, in the context of a molecular phylogeny of Phyllotis, as member of the P. andium/amicus group (Steppan et al. 2007). We also report the standard karyotype of this species and comment on its natural history. We further identify an area of endemism in the northwestern Andes of Peru, where the new species and other sigmodontines coincide in patterns of distribution.
Methodology: The new species was in detail compared with other species of Phyllotis, mainly those of the andium/amicus group. Four external and 20 cranial and dental measurements from adult specimens were employed in descriptive statistics. Sexual dimorphism was evaluated in Phyllotis nov. sp. and P. andium using the t test. Then, to compare the new species with P. andium, all cranial and dental measurements were used in principal component analyses (PCA) of the covariance matrix of log-transformed measurements. Chromosome preparations were obtained from bone marrow, following Ford and Hamerton (1956).
Results: Phyllotis nov. sp. is distinguished from all other congeneric species by the combination of a relatively short tail and distinctive cranial morphology, including an comparatively long incisive foramen, a long palate that extends posteriorly beyond M3, mesopterygoid fossa without medial process, squamosal ridge relatively pronounced, ectotympanic large and easily visible from dorsal view, and capsular process inconspicuous or absent. The biplots of PCA show two clearly separated groups, one shaped by specimens of the new species and the other by P. andium; the new species is located mainly on the positive side of the first axis whereas P. andium on the negative side. The diploid number (2n) is 48 and the autosomal fundamental number (FN) is 72.
Discussion and conclusions: The new species of Phyllotis is endemic to the Puna ecoregion of northern Peru. This discovery supports the hypothesis of a generalized biogeographical subdivision in the Puna of northwestern Peru where the ranges of several sigmodontine species coincide in an area limited by the Río Santa, the Río Marañón, and the Huancabamba depression. Based on the presence of numerous crocentric chromosomes and the available molecular data we propose a restricted andium group to include P. andium, P. definitus, and the new species. We also summarize available data on natural history, habitat preferences, reproduction, and the systematic position of this species. The species may be threatened due to its restricted distribution, the relatively high anthropic activity in the region, and its absence in any protected area.

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