Submitted to: International Symposium on Biological Control of Arthropods
Publication Type: Proceedings
Publication Acceptance Date: 5/2/2005
Publication Date: 9/12/2005
Citation: Hopper, K.R., Farias, A.M., Woolley, J.B., Heraty, J.M., Britch, S.C. 2005. Genetics: relation of local populations to the whole "species" - implications for host range tests. Second International Symposium on Biological Control of Arthropods. p 665-671. Interpretive Summary: Host specificity is crucial for the safety of biological control introductions. Review of the literature on variation in host specificity among populations and sibling species of parasitic wasps used in biological control and analysis of new data from parasitic wasps that attack aphid pests yielded the following conclusions for biological control practice: (1) parasitic wasps in what appears to be a single species, but collected from different regions or host species, may differ greatly in host specificity and thus should have their host ranges tested separately, and (2) sibling species from different regions with different patterns of host use may exchange genes if brought together, which could lead to evolutionary changes in host use and effects on non-target species.
Technical Abstract: Populations of parasitoids from different host species or regions can differ in host specificity. Here, we review the literature on variation in host specificity among populations and sibling species of parasitoids. We also summarize our results on the evolution of host specificity in the APHELINUS VARIPES species complex. Populations of A. VARIPES from DIURAPHIS NOXIA, ROPALOSIPHUM PADI, and APHIS GLYCINES collected throughout Eurasia differed in parasitism of seven aphid species in no-choice laboratory experiments. Some populations showed narrow to monospecific host use, others attacked most or all host species tested. Most populations were reproductively isolated. However, some allopatric populations where partially or completely reproductively compatible in laboratory crosses, although they differed in host specificity. A molecular phylogeny indicated that these compatible, allopatric populations are distinct lineages, and morphometric analyses showed subtle differences between them. Phylogentic affinity was a poor indicator of similarity in host use. We have been able to introgress genes for use of a novel aphid species from one parasitoid species to another in laboratory crosses. The take-home lessons for biological control are: (1) parasitoids in what appears to be a single species, but collected from different regions or host species, may differ greatly in host specificity and thus should be tested separately, and (2) allopatric sibling species with different patterns of host use may introgress if placed in sympatry, which could lead to evolutionary changes in host use.