Within‐population craniometric variability of insular populations of deer mice, Peromyscus maniculatus, elucidated by landscape configuration

Abstract

Within‐population genetic variability of twelve insular and four mainland populations of deer mice (Peromyscus maniculatus) was assessed using craniometric characters, and compared to results previously obtained from RAPD data. An index of Craniometric Variance (CVar) was computed from pairwise distances among all specimens. Variations in CVar measures were then compared to landscape variables using a linear regression approach. Our results suggest that CVar decreases in presence of large number of a competitive species (the boreal redback vole, Clethrionomys gapperi; r=−0.527, p<0.037) in deer mouse populations. Island remoteness (r=−0.251, p<0.220) and the geometry of the bank opposite to each island (r=−0.459, p<0.067) were marginally correlated with CVar, but the linear combination of these two variables, forming a composite isolation index, represented the major factor explaining the observed CVar (r=−0.648, p<0.011). Using a multiple regression model, 76.3% of the CVar was explained by a combination of this isolation index and the competitors’ abundance. These results suggest that taking into account landscape barriers as well as the dispersal behavior of small mammals might provide sounder ecological variables than geographical distances alone for predicting within‐population genetic variability in a network of habitat patches.