Genetic Differentiation among Populations of the Rare Mayfly Siphlonisca aerodromia Needham

We used 5 species-specific microsatellite DNA markers to assess genetic differentiation among 6 populations (4-226 km apart) of the rare mayfly Siphlonisca aerodromia Needham in Maine. All populations, even those 4 km apart and from the same river drainage, showed significant differences in allele frequencies, and all subpopulation fixation indices based on infinite allele mutation models (F st ) and stepwise mutation models (R st ) were significantly different from 0. However, a hierarchical analysis of F st and R st values among sets of populations indicated that the most substantial pattern of differentiation was between the 2 populations from the Kennebec drainage in western Maine and the 4 populations from the Penobscot and St. Croix drainages in central and eastern Maine. We found no evidence for significant linkage disequilibrium among alleles at any locus in any population, suggesting that parthenogenesis is not an important mode of reproduction in these insec...