Morphologic Variation between Long-established and Pioneer Populations of the Meadow Vole (Microtus pennsylvanicus) in Illinois

Abstract

Variation in cranial dimensions was studied within and between two populations of Microtus pennsylvanicus in Illinois. One population has only colonized the Champaign County area in the last decade; the other has long inhabited the northern half of Illinois. Univariate statistics, as well as multivariate analysis of variance (MANOVA), principal component and discriminant function, were used to test for divergence in cranial morphology between the populations. These comparisons showed no significant differences in the population means or in the degree of variation, at least as compared to geographic variation between Illinois animals and specimens of an Ohio population of the same subspecies. Results are discussed with regard to population genetic theories concerning range expansions.