Microgeographic Variation in the Mexican Vole, Microtus mexicanus

Altitudinal variation was assessed in 115 (62 male; 53 female) Mexican voles (Microtus mexicanus) from six localities in Jalisco, Mexico. Univariate and multivariate statistical techniques were employed in the data analyses. A total of 49 skeletal measurements were investigated, and of these, 17 showed significant interlocality variation. Rostral breadth, depth of braincase, rostral height, width of third molar and nasal length were found to be the most variable characters. Component I (a size factor) accounted for 36% of the total phenetic variation; components II and III accounted for 30% and 19%, respectively. Larger individuals were found to occur at lower altitudes; smaller individuals occurred at higher altitudes. Size variation was expressed in reverse to Bergmann\u27s Ecogeographical Rule