A morphological and genetic comparison ofPatrobus fossifrons(Eschscholtz) andPatrobusstygicusChaudoir (Coleoptera: Carabidae)

Abstract

Specimens of Patrobus fossifrons (Eschscholtz) and Patrobus stygicus Chaudoir were examined for morphological and enzymatic characteristics. Differences in both character types were found between the species. Differences were also found among populations of P. fossifrons; a "coastal" morph and an "inland" morph are described and their biogeographical history is traced to glacial refugia. Patrobus stygicus populations were homogeneous for all characters studied. Patrobus stygicus and inland P. fossifrons co-occurred at Cypress Hills and in the Pincher Creek area in Alberta. No evidence of hybridization was found at Cypress Hills. At Pincher Creek, 2 out of 299 beetles examined were hybrids, but there was little evidence that this rate of hybridization had resulted in any gene flow between the species. Patrobus stygicus and coastal P. fossifrons co-exist and hybridize in central Washington State. Electrophoretic analysis of a mixed-stock specimen proved that at least some hybrids are fertile. However, a combination of hybrid disadvantage and low hybridization rates keeps gene-flow levels very low. It is concluded that despite a small amount of hybridization, P. stygicus and P. fossifrons remain separate species.