Microsatellites and 16S sequences corroborate phenotypic evidence of trans-Andean variation in the parasitoid Microctonus hyperodae (Hymenoptera: Braconidae)

Diversity, population structure, and individual behaviour of parasitoids as seen using molecular markers

Parasitoids have long been models for host-parasite interactions, and are important in biological control. Neutral molecular markers have become increasingly accessible tools, revealing previously unknown parasitoid diversity. Thus, insect communities are now seen as more speciose. They have also been found to be more complex, based on trophic links detected using bits of parasitoid DNA in hosts, and host DNA in adult parasitoids. At the population level molecular markers are used to determine the influence of factors such as host dynamics on parasitoid population structure. Finally, at the individual level, they are used to identify movement of individuals. Overall molecular markers greatly increase the value of parasitoid samples collected, for both basic and applied research, at all levels of study.

Host-adapted parasitoids in biological control: does source matter?

It has been hypothesized that the success of a biological control introduction is, in part, dependent on the ability of the control agent to become established in its new environment or to its new population of hosts through local adaptation. Despite this, few studies have investigated the influence of the recent coevolutionary history of pest species and natural enemies on the efficacy of biological control agents, especially for agents that are mass-reared for release in agriculture. We investigate the evolutionary potential of a biological control agent Aphidius ervi to adapt to a key pest species, the foxglove aphid Aulacorthum solani, through components essential to the evolution of parasitoid virulence. We explored (1) the influence of genetic variation from natural source populations on the ability to parasitize natal and non-natal host species; (2) the heritability of key traits related to parasitoid fitness; and (3) the efficacy of parasitoid host-selection lines in a greenhouse system. Source populations maintained genetic variation in the ability to utilize natal and non-natal host species; however, only some of the traits sampled suggested local adaptation of parasitoid populations. The ability to parasitize a host was found to be genetically determined and strongly heritable, irrespective of host species. The greenhouse study demonstrated the potential of parasitoid selection lines to substantially increase performance of parasitoids for target pest species. This research provides insight into novel techniques that can be used to increase the quality of biological control agents through the development of lines of natural enemies adapted to particular pest species.

Hosts are more important than destinations: What genetic variation in Microctonus aethiopoides (Hymenoptera: Braconidae) means for foreign exploration for natural enemies

Nucleotide sequence data were generated from the gene regions COI, 16S, and arginine kinase to assess genetic variation within the Palearctic parasitoid, Microctonus aethiopoides, reared from Sitona discoideus, S. hispidulus, and Hypera postica collected from two proximate locations in Mediterranean France. Partitioned Bayesian phylogenetic analyses of the molecular data provided strong support for the presence of at least two M. aethiopoides biotypes, one associated with Hypera species and the other with Sitona species. These new results combined with previously published data from 14 countries show that M. aethiopoides genetic variation is much more strongly correlated with host taxon than with sampling location. This contrasts with earlier perceptions that M. aethiopoides exhibits significant geographic variation, and helps to explain the widely varying biological control outcomes that have been obtained following the introductions of M. aethiopoides to Australia, New Zealand, and North America. The results strongly suggest that success rates and environmental safety in biological control would both be improved by ensuring that parasitoids collected in the native range are reared from the same host species as the one being targeted for control in the region of introduction. The results also provided insights both on the evolution of M. aethiopoides' host range, and on its evolutionary transition between solitary and gregarious larval development.