Genetic variation in stream mayfly (Insecta: Ephemeroptera) populations in eastern North America

350 210 Stroud Water Research Center

Sweeney. B.W., D.H. Funk, and R.L. Vannote. 1987. Annals of the Entomological Society of America 80:600–612.

doi: 10.1093/aesa/80.5.600


We evaluated genetic variation in 40 populations (five species) of ephemerellid mayflies collected from streams in the Atlantic and Gulf drainages of eastern North America. The principal study species included Eurylophella funeralis (McDunnough), Eurylophella verisimilis (McDunnough), Ephemerella subvaria McDunnough, Ephemerella aurivillii (Bengtsson) and Ephemerella septentrionalis McDunnough. For the 40 populations, proportion of polymorphic loci averaged 22.3% (SEM = 2.0; range, 0–50%), with relatively low genie heterozygosity (ݲ ± SEM = 0.079 ± 0.006; range, 0–0.160). Nei’s genetic distance (D) averaged 0.006 among conspecific mayfly populations and 1.434 among species. A genetic distance of 0.704 suggests that Eu. funeralis and Eu. verisimilis are distantly related congeners. Genetic distances among populations of the three principal Ephemerella species were even higher, with D values averaging >1.0. Genetic distance data for five additional Ephemerella species, Ephemerella dorothea Needham, Ephemerella excrucians Walsh, Ephemerella inconstans Traver, Ephemerella invaria (Walker), and Ephemerella rotunda Morgan, revealed that D values <0.6 may be more typical of closely related ephemerellid species. Nevertheless, the biochemical data suggest that the currently accepted classification of these genera should be reassessed. Significant genetic differentiation among geographic populations was observed for many loci of each species, with average FST values ranging from 0.04 to 0.15 (average for five species = 0.10). Although one allele generally predominated at each polymorphic locus of a given species, there was significant variation in allele frequencies among populations. However, allele frequencies did not exhibit a geographic cline. Gene flow seems limited among most mayfly populations. A severe deficiency of heterozygotes at several loci for each species indicates substantial inbreeding in mayfly populations (average FIS values ranged from 0.03 to 0.28). Heterogeneity of inbreeding values among loci in a given species suggests possible selection at some loci.