Local scale population genetic structure of Entomophthora muscae epidemics

Isolates of the entomopathogenic fungus Entomophthora muscae were obtained from houseflies sampled at five stables on Zealand during an epidemic in fall 2005. DNA fingerprints were generated from single conidia from 40 E. muscae isolates using the PCR-based method of Inter-Simple Sequence Repeats (ISSR). This resulted in fingerprint patterns consisting of about 50 fragments, of which, 14 were polymorphic. From the polymorphic loci we estimated the reproductive mode, genetic differentiation and gene diversity of E. muscae populations using the statistics of index of association, Weir & Cockerhams theta and Nei's analysis of gene diversity in subdivided populations. Our results revealed no significant differences in allele frequencies among the five populations. The index of association test rejected the null hypothesis of random mating, but the test for paired locus compatibility showed weak or no linkage between loci indicating recombination or homoplasy in the dataset. From this study we cannot exclude the possibility that the population genetic structure underlying E. muscae epidemics could be panmictic consisting of several lineages with a high level of reciprocal migration.