Microsatellite marker variation in populations of the melon fly parasitoid, Psyttalia fletcheri

Abstract

The parasitoid Psyttalia fletcheri (Silvestri) is an important natural enemy of the melon fly, Bactrocera cucurbitae (Coquillett). Melon fly infestations are responsible for extensive losses of cucurbit production worldwide, and P. fletcheri has been used for some time in biological control programmes attempting to deal with this pest. However, there is a general lack of knowledge of the genetic structure of populations of P. fletcheri, and the development of this information is key to the effective use of this parasitoid. In this study, we isolated several novel microsatellite loci to investigate the genetic structure of P. fletcheri populations from six locations in Thailand. All the loci analysed here were polymorphic, and the mean number of alleles per locus ranged from 4.2-8.6. Heterozygote deficiencies were noticed in most populations. Overall FST estimates showed moderate genetic differentiation among P. fletcheri populations with a jackknife mean of 0.084. However, pairwise FST calculations revealed that 11 out of 15 population comparisons showed genetic differentiation. The greatest level of differentiation was also found for the population that had the lowest value for genetic diversity. In contrast, populations with high levels of genetic variation did not show significant genetic differentiation, nor did they show significant isolation by distance. An unrooted dendrogram constructed from Nei's genetic distance values also confirmed that one population from the south of Thailand can be separated from the others.