Geometric morphometrics clarifies the taxonomic status of semifossorial shrews (Eulipotyphla, Soricidae, Cryptotis) from Mexican cloud forests

Abstract

The small-eared shrews Cryptotis mexicanus and Cryptotis obscurus (Eulipotyphla, Soricidae) are two closely related taxa from the northern Neotropics whose taxonomy is still unresolved. Here, we tested the hypothesis of three lineages (Northern, Central, and Southern) within this pair of semifossorial shrews. We photographed skulls, dentaries, and humeri from 226 museum specimens and used geometric morphometrics to evaluate sexual dimorphism, differences between lineages, and the effect of the environment on the shape of the structures. We found negligible differences between males and females, supporting previous studies of classical morphometrics in this genus. Our results also support the differentiation of semifossorial shrews into the three geographically isolated groups, where the size of the dentary and the shape of the three examined structures contribute to discrimination. We found a significant sign of the influence of the environment on the shape of the dentary but not on the skull or the humerus. We suggest that geographic isolation across climatically similar regions has contributed to the differentiation between lineages. We propose recognizing all three lineages as valid species that must be adequately described.