The parasitoid wasp Mastrus ridens (Hymenoptera: Ichneumonidae) is a particularly well-suited biological model to document the history and evolution of populations used in classical biological control, repeatedly introduced in various environments and moved from laboratory to laboratory worldwide. This specialist ectoparasitoid of the codling moth was first imported from Kazakhstan to the USA in the 1990’s, and then sent to Argentina, Chile and New Zealand. More recently, it was sent to Australia and France from other laboratory colonies, and imported again from field collections in Kazakhstan to Chile. We used DNA sequencing to confirm the taxonomic identity of several populations used for biological control worldwide, and developed microsatellite markers to compare the genetic diversity of laboratory and field populations and evaluate genetic differentiation between them. Also, the occurrence of diplod males was evaluated with microsatellites and flow cytometry.
Results/Conclusions
Morphological and molecular tools confirmed that insects sampled in 1994-1998 belong to the same species of those collected in 2013. A kit of 11 microsatellites was developed and validated. A total of 185 individuals from five populations were tested to compare different measures of genetic diversity using microsatellites. Genetic diversity and differentiation were congruent with the historical data available, with the highest diversity in the wild collected individuals and lower in the population that has been longer in captivity and suffered several bottlenecks. The genotyping of males with the developed markers revealed the occurrence of diploid males, which was further confirmed by flow cytometry, suggesting a complementary sex determination (CSD) mechanism in this species. The percentage of diploid males in the studied populations ranged from 4% to 30%, which is consistent with a single-locus CSD. Molecular tools proved to be suitable and reliable for genetic diversity analyses in M. ridens, and should be implemented more frequently in classical biological control programs. Funding: FONDECYT 1131145.