Cotesia congregata: local adaptation or host-plant races?

Cotesia congregata (Say) is a gregarious endoparasitoid of larval sphingids, most of which are plant family specialists. Local adaptation of this species to two hostplants of Manduca sexta L., tomato and tobacco, has been reported previously. Genetic differentiation of multiple populations of C. congregata collected from M. sexta on tobacco (Solanaceae: Nicotiana tobacum) or Ceratomia catalpae (Boisduval) on Catalpa spp. (Bignoniaceae) within the mid-Atlantic region was evaluated using seven microsatellite loci and the mitochondrial COI locus. Additional collections were made at one “catalpa site” where tobacco was experimentally introduced. Measures of genetic variance and phylogenetic analyses indicate the presence of distinct host-plant races in C. congregata.