Morphological variation in the Cerralvo Island pocket mouse Chaetodipus siccus from the Baja California Peninsula, México

Abstract

Chaetodipus siccus is a microendemic species with a restricted distribution and two geographically isolated populations, one on Cerralvo Island and its counterpart on the Baja California Sur peninsula, each associated with dissimilar environmental conditions.  The hypothesis to test is that each population is adapted to its distinct environment and has its own evolutionary trend that can be used to differentiate them. The analysis of the skull shows that each population has a differential development of the region associated with chewing muscles.  The statistical analyses of the Procrustes (shape) and Mahalanobis (size) distances confirm these differences statistically (P < 0.05).  The set of differences in skull shape associated with the chewing muscles, craniodental measurements, external morphological traits, genetic isolation, and association with a different environment support the hypothesis that each population has its own evolutionary tendency.