Cranial shape variation and phylogenetic relationships of extinct and extant Old World leaf-nosed bats

Abstract

The leaf-nosed bats in Hipposideridae and Rhinonycteridae currently have an Old World tropical to subtropical distribution, with a fossil record extending back to the middle Eocene of Europe. The Riversleigh World Heritage fossil site in northwestern Queensland constitutes a particularly rich archive of faunal diversity for Old World leaf-nosed bats, having yielded more than 20 species. We used 2D geometric morphometrics to quantify cranial shape in hipposiderids and rhinonycterids, with the aim of referring unallocated fossil species, particularly from Riversleigh, to each family within a phylogenetic framework, and using a quantitative approach to reconstruct cranial shape for key clades in these Old World radiations. Our sample comprised 21 extant hipposiderids and rhinonycterids, 1 megadermatid and 1 rhinolophid, in which 31 landmarks were placed in lateral and ventral views, and five measurements were taken in dorsal view. The phylogeny used as the framework for this study was based on an analysis of 64 discrete morphological characters from the dentition, cranium and postcranium scored for 42 extant and fossil hipposiderids and rhinonycterids and five outgroup taxa (rhinolophids and megadermatids). The phylogenetic analysis was conducted using maximum parsimony, with relationships among selected extant taxa constrained to match the results of recent comprehensive molecular studies. Our phylogenetic results suggest that the Riversleigh leaf-nosed bats probably do not represent an endemic Australian radiation, with fossil species spread throughout the tree and several with sister-group relationships with non-Australian taxa. Discriminant analyses (DA) conducted separately on each dataset resulted in cross-validated classification success ranging from 61.9% for ventral landmarks to 71.4% for lateral landmarks. Classification of the original grouped cases resulted in success of 81% for each dataset. Of the eight fossil taxa included as unknowns in the DA, six were found to be assigned to the same group as recovered by the phylogenetic analysis. From our results, we assign the Riversleigh Miocene species <i>Archerops annectens,Brachipposideros watsoni, Brevipalatus mcculloughi, Rhinonicteris tedfordi</i> and <i>Xenorhinos halli</i> to Rhinonycteridae, and <i>Riversleigha williamsi</i> and <i>Hipposideros bernardsigei</i> to Hipposideridae. Our results support <i>Pseudorhinolophus bouziguensis</i>, from the early Miocene of Bouzigues in southern France, as belonging to Hipposideridae, and probably <i>Hipposideros</i>. The reconstructed ancestor of hipposiderids was distinguished from that of the rhinonycterids by having a shorter rostrum, and less of a distinction between the rostrum and braincase.