Landmark-Based Size and Shape Analysis in Systematics of the Plecotine Bats

Abstract

Morphometric divergence among the skulls of 10 species of plecotine bats (n = 105) was studied using x, y-coordinates of 11 homologous landmarks recorded from the left half dorsal view of each skull. Univariate and multivariate analyses of shape coordinates provided estimates of differences among taxa and between sexes. The differences in size among species were correlated with uniform shape differences. The centroid size to uniform factor allometry was more pronounced longitudinally (i.e., along the midline of the skull) than it was laterally. Significant shape differences among species were also detected in both uniform and non-uniform components. Non-uniform shape variation involved lateral rather than longitudinal displacement of landmarks on the skull. Sexual dimorphism was reflected by centroid size and was seen only in Otonycteris hemprichi, in which females were about 4.4% larger than males. The UPGMA phenograms of Mahalanobis D ² of shape coordinates and of relative warp scores (in which the uniform shape component had been removed) revealed two consistent phenetic clusters. One was formed by O. hemprichi, with the remaining genera grouping in a second cluster. The relationships among genera in this second cluster varied depending on the phenogram generated. Nevertheless, the UPGMA phenogram derived from Mahalanobis D ² computed on Bookstein shape coordinates (sexes combined) was entirely congruent with the current systematic hierarchy and phylogenetic hypothesis of the Plecotini sensu stricto recently put forward based on a parsimony analysis of 32 skin and skull characters. In our analysis, the most divergent species group was the monotypic O. hemprichi. A second group was formed by the genus Barbastella. The remaining clusters were composed of species of Corynorhinus; Plecotus; and a cluster containing Idionycteris and Euderma.