The genetic population structure of lotic and lentic mayflies of theBaetis vernusgroup (Ephemeroptera: Baetidae)

Abstract

AbstractNymphs of lotic mayflies live in environments that are expected to give rise to different degrees of population structuring. Here we investigate two taxa adapted to different lifestyles.Baetis macaniKimmins (Ephemeroptera: Baetidae) lives in flowing water; brooks that may periodically dry out in the summer or freeze to the bottom in winter.Baetis jaerviiSavolainen is mostly found in sedge belts along the shores of lakes. Most insects living in flowing water show low levels of among-population genetic differentiation within and among catchments. Levels of differentiation in the lotic species are therefore assumed to be lower than in lenticB. jaervii. Here we test this hypothesis. Mitochondrial DNA and allele frequencies of nuclear genes were used to detect population structure in specimens originating from an extensive area from northern Finland. The genetic differentiation among populations of the loticB. macaniis more than twice the corresponding value for the lenticB. jaervii(FST0.33 versus 0.15, while the meanFSTbetween species was 0.33 and significant). The result is congruent within the cytochrome c oxidase subunit I gene (COI) partial gene frequencies. We argue that the significant genetic population structure, which only was found in the loticB. macani, is differentiated as a consequence to the unpredictable environment as contrasted to the stable environment in standing bodies of water.