Genetic diversity of a microsporidium parasite (Kneallhazia solenopsae) and its fire ant host species (Solenopsis invicta) in South America

Microsporidia comprises nearly 1,300 species of single-celled, obligate intracellular, spore forming eukaryotic parasites that infect every major animal group. They are pathogens of insects, causing disease in both beneficial and pest species. Despite the medical and agronomical importance, molecular epidemiology data of microsporidia species are scarce. Understanding the processes that maintain and generate microsporidial genetic diversity within and among host populations has broad implications for understanding microsporidia evolution and disease dynamics. For parasites, the genetic structure of the populations is not only modulated by intrinsic features such as transmission modes, life-history strategies (i.e. host specificity, dispersal), but also by the population dynamics of the host. Thus, diversification processes would be better understood through the study of coevolutionary interactions between host and parasites. Here, we study the coevolution in a system composed of a microsporidium (Kneallhazia solenopsae) that occurs in a fire ant host species (Solenopsis invicta). Microsporidia prevalence was evaluated using a polymerase chain reaction (PCR) assay in 767 colonies from 20 localities in South America (native range). Ten microsporidia haplotypes of concatenated sequences from three nuclear genes (1,390 bp) were described from 11 host colonies. Individual ants from each colony were genotyped using 67 microsatellite loci. Comparisons of host and parasite genetic distance matrices suggest that genetically similar host populations have genetically similar parasites. This concordant geographic pattern in the genetic differentiation among host-parasite populations suggests that host and parasite undergo similar levels of gene flow. The implications for local adaptation will be discussed.