Paleophylogeography of Notiosorex desert shrews with description of a new species

The genus Notiosorex is the only group of shrews in North America with adaptations to arid or semiarid zones. The genus was described with a single variable species, Notiosorex crawfordi, from which 5 new species have since been distinguished. To date, the phylogenetic relationships of Notiosorex species have only been partially analyzed and it is possible that there are still distinct species included within the catch-all of N. crawfordi. Here, we use geometric morphometrics on cranial and mandibular characters of the described extant species, 3 fossil species, and a distinctive population of N. crawfordi as a proxy for an integrated assessment of phylogenetic relationships of all Notiosorex species. Our results indicate that the population from the Altiplano Mexicano is more similar to, yet distinct from, N. villai than it is to N. crawfordi—we describe it as a new species. We also used the resulting tree to reconstruct phylogeographic history within the genus, which suggests that Notiosorex sp. nov., N. villai, N. evotis, and N. tataticuli all diverged allopatrically as populations from the ancestral area that is currently occupied by N. crawfordi (and in the deeper past by the fossil species N. harrisi), and pushed south into the Gulf Coast, the Altiplano, and Baja California within the last 5 million years following the end of the Miocene.