Submitted to: Molecular Phylogenetics and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/21/2007
Publication Date: 7/12/2007
Citation: Heraty, J.M., Woolley, J.B., Hopper, K.R., Hawks, D.L., Kim, J., Buffington, M. 2007. Molecular phylogenetics and reproductive incompatibility in a complex of cryptic species of aphid parasitoids. Molecular Phylogenetics and Evolution. doi:10.1016/j.ympev.2007.06.021. Interpretive Summary: Discrimination among species of natural enemies is crucial to the success and safety of biological control introductions because even closely related species may have different host specificities. Studying a major group of aphid parasites, we found that species that appear very similar using a traditional morphological approach were different using DNA sequence data. These species also had different host ranges and were reproductively isolated. The DNA sequence data allowed us to infer which species of parasitic wasps were most closely related. This will allow us to determine whether host specificity is more similar among more closely related species, which will help in predicting whether introduced parasitic wasps will attack non-target species.
Technical Abstract: Relationships among different geographic and host populations in the Aphelinus varipes species complex were analyzed with a combination of four nuclear and two mitochondrial gene regions. Within the varipes complex, populations were from Diuraphis noxia and Rhopalosiphum padi in Georgia, France and Israel (R. padi only), and from Aphis glycines from Japan and China. Outgroups include Marietta montana, Aphelinus asychis reared from D. noxia and R. padi, and Aphelinus mali (USA) and Aphelinus near mali (Russia). A combined analysis of 19 genotypes resulted in 8 most-parsimonious trees, of which the strict consensus was almost fully resolved. Removal of COI variants resulted in a single most parsimonious tree with high bootstrap and Bremer support. Gap coding was concordant with substitution changes,and provided the only support for monophyly of the two Asian populations. The varipes complex was strongly supported, and except for one COII substitution, there was no data conflict; however, five of the gene regions and indels were necessary to fully resolve relationships. The Aphelinus mali complex was sister group to the varipes complex in parsimony analyses. Four distinct clades within the varipes complex were recognized: Georgia ex R. padi; France ex D. noxia + A. hordei ex D. noxia; Georgia ex D. noxia + France ex R. padi + Israel ex R.padi; and Japan + China ex A. glycines. Two of these groups, Georgia ex R. padi and France ex D. noxia were reproductively isolated from each other and to the other populations, and Georgia ex D. noxia and France ex R. padi were only partially compatible with each other. These results were reinforced by the proportional number of base substitutions and indel events on the single most-parsimonious tree. The molecular evidence supports the isolation of a number of distinct sympatric or allopatric lineages consistent with the recognition of several cryptic species.