Genetic divergence in shrews (Mammalia: Soricidae) of humid montane forests north of the Neotropics

Abstract

Shrews of the Cryptotis mexicanus group (Mammalia, Soricidae) are closely associated with the humid mountain forest north of the Neotropics. Within this group, phylogenetic studies have defined a monophyletic group composed of 3 species: C. nelsoni as sister of the clade C. obscurus - C. mexicanus. The pattern of morphological variation and estimates of potential distribution suggests that its evolution is tightly associated with the altitudinal changes induced by the last glacial-interglacial cycles. In this study, we analyzed 70 mitochondrial sequences of the Cytochrome b for this clade using phylogeographic and phylogenetic analyses to test whether the valleys, canyons, and plains along the distribution of this group could be promoting its genetic structure and differentiation. The results indicate 4 genetic groups, partially congruent with previous studies; one corresponds to C. nelsoni, while the other 3 appear within the clade C. obscurus - C. mexicanus. The genetic divergence observed among the 4 groups suggests the influence of some geographical barriers, from valleys and canyons to volcanoes, which through the last glacial-interglacial cycles could have shaped the current genetic pattern variation. Our findings also suggest that the taxonomy between C. obscurus and C. mexicanus is not yet resolved.