Hybridization between subspecies of Canthon humectus (Say) (Coleoptera: Scarabaeidae)

Hybridization zones constitute privileged natural laboratories to study differences among taxa and the processes that originate patterns of geographic variation. In this study, we investigate a hybridization zone between two subspecies of coprophagous beetles, Canthon humectus hidalgoensis Bates and Canthon humectus alvarengai Halffter (Coleoptera: Scarabaeidae: Scarabaeinae), in central Mexico. We also describe the variation of four characters - dorsal surface coloration, total length, pronotal granulation, and aedeagal morphology - throughout the hybridization zone, which clearly define the transition among typical localities for both subspecies. We propose that superposition of the area of distribution of both subspecies, as well as the lack of reproduction barriers between different morphs, allow the existence of geographical variation.