Species limits in mesoamerican Aulacorhynchus toucanets

Abstract

We examined geographic patterns of variation and differentiation in morphological characters of the emerald toucanets (Aulacorhynchus spp.) of Mesoamerica. Bill lengths showed flat freequency distributions, suggesting that no "adult" size is reached, and raising the possibility that bill growth in toucanets may be indeterminate. Sparse lowland populations in the Peten region are of uniformly small body size, suggesting that they may consist of subadult individuals. Patterns of variation support recognition of four species in Mesoamerica: A. wagleri in western Mexico, A. prasinus in eastern Mexico and northern Central America, A. caeruleogularis in Costa Rica and western Panama, and A. cognatus in eastern Panama, as well as several additional forms (A. lautus, A. albivitta, and A. nigrogularis) in South America.