AreAltica carduorumandAltica cirsicola(Coleoptera: Chrysomelidae) Different Species? Implications for the Release ofA. cirsicolafor the Biocontrol of Canada Thistle in Canada

Altica carduorumandAltica cirsicolaare two species of leaf-feeding beetle (Coleoptera: Chrysomelidae) which appear to be morphologically indistinguishable and reportedly hybridize in the laboratory. A European population ofA. carduorumwas previously screened for host-plant specificity and released in North America for the control of Canada thistle,Cirsium arvense.A population ofA. cirsicolafrom China is currently being considered as a biocontrol agent forC. arvenseand, as a different beetle species, must be screened using host-specificity tests similar to those used forA. carduorum.IfA. carduorumandA. cirsicolaare, in fact, one species, the screening requirements forA. cirsicolacould be significantly reduced. Hence, we investigated the taxonomic relationship betweenA. carduorumandA. cirsicolausing morphometric analyses, hybridization experiments, and DNA fingerprinting using random amplified polymorphic DNA (RAPD) analysis. Discriminant function analyses indicate thatA. carduorumandA. cirsicolacannot be reliably distinguished by their morphologies, and interspecific matings produce fertile F1offspring. However, because interspecific matings produce significantly fewer offspring than intraspecific matings, and because of clear differences in their DNA profiles, we conclude thatA. carduorumandA. cirsicolaare separate species. This study serves to highlight the value of genetic analyses in taxonomic studies and their role in biological control programs.