Wither the subspecies? An ecological perspective on taxonomic, environmental and sexual determinants of phenotypic variation in big-eared woolly bats, Chrotopterus auritus

Continuous phenotypic variation reflecting geographical clines can be difficult to distinguish from subspecific discontinuities when specimens are few and heterogeneously distributed. Nonetheless, increases in the holdings of museum collections over recent decades contribute to our ability to resolve more fine-scaled phenotypic gradients for many species. Although the big-eared woolly bat (Chrotopterus auritus) is not commonly encountered and thus poorly represented in museum collections, sufficient numbers have accumulated to allow an assessment of subspecific, sexual, spatial and environmental components of phenotypic variation. I examined 123 specimens from across the distribution of C. auritus and characterized the phenotype based on external, cranial and mandibular characteristics. I decomposed variation into components based on univariate and multivariate statistical analyses. All components accounted for significant phenotypic variation. Nonetheless, when examined together and after accounting for correlated variation among components, only sexual, spatial and environmental components accounted for significant unique variation. This, combined with the observation that all qualitative characteristics used to define subspecies of C. auritus can be observed throughout its geographical range, suggest that phenotypic variation is clinal and not characterized by discontinuities reflective of subspecies. Clinal variation was most strongly related to temperature and its seasonality, highlighting the important role played by these climatic characteristics in many aspects of the biology of Phyllostomidae.