An electrophoretic, morphological, and ecological investigation of a putative hybrid zone between Myotis lucifugus and Myotis yumanensis (Chiroptera: Vespertilionidae)

Abstract

In the Okanagan valley of British Columbia, Myotis lucifugus and Myotis yumanensis are sympatric and some individuals are intermediate in typical morphology. A survey of electrophoretic variation at 31 protein loci of intermediate bats indicates no evidence of hybridization. Discriminant analysis on these specimens shows better separation by skull characters than by external measurements, but 13 bats (14% of 93 examined) were designated as intermediate and 7 could have been labelled hybrids. Absence of electrophoretic evidence of hybridization indicates that similar morphology reflects overlap in extremes of intraspecific morphological variation. Myotis lucifugus was trapped in the western foothills adjacent to the Okanagan River and foraged in all of the habitats we sampled. Myotis yumanensis was only trapped in the valley and preferred to forage over flowing water. There was no evidence of agonistic interactions between the two species. The composition of the diets in M. lucifugus and M. yumanensis changed over the course of this study and there were significant differences in the proportions of insect taxa consumed by the two species. Parturition in M. lucifugus commenced after mid-June and most females did not produce offspring until their 2nd year, whereas parturition in M. yumanensis commenced in early June and female offspring gave birth in their 1st year.