Mensural discrimination of Myotis (Chiroptera, Vespertilionidae) in the southeastern United States

Abstract

Discriminant functions were constructed using external and cranial measurements to distinguish the six species of Myotis that occur in the southeastern United States. Twenty-three morphological characters were measured from 161 specimens of Myotis. Differences among species for morphological characters were examined using analysis of variance and discriminant analysis. A bootstrap procedure was used to validate the final discriminant model using all six species. Differences were observed among species for all 23 characters measured in univariate tests, but the range of values for most species overlapped the range of other species. Bootstrap analyses indicated that our discriminant functions constructed using both external and cranial measures allowed correct identification of 99.4% of specimens examined. Discriminant models constructed using only cranial characters permitted correct identification of 96.9% of specimens examined. Univariate analyses were not reliable because variation within species prevented unambiguous identification of any species based on a single character. However, Myotis species in the southeastern United States can be distinguished with a high level of accuracy using multivariate techniques when a sufficient number of measurements are used.