Effect of habitat fragmentation by Dams and Intermittent River on Dispersal of Freshwater Insect Epeorus latifolium

We investigated gene flow of Epeorus latifolium in Shigenobu River (Ehime, Japan) fragmented by 3 types of barriers (i.e. one reservoir dam, 98 weir&check dam, intermittent flow). 112 individuals (13 - 15 individuals / population, average = 14) were collected from 8 populations and genotyped using Cytochrome Oxidase subunit I region in mitochondrial DNA. Among the 3 types of habitat barriers, the weir&check dams showed significant and the highest pairwise Fst between fragmented populations. In addition, the number of weir&check dams was significantly and positively correlated to the level of pairwise Fst (R = 0.81, p < 0.05), suggesting that gene flow of E. latifolium tends to be interrupted in sections with large number of weir&check dams (at least > 14). However, this genetic differentiation found in mountain area could be also explained by the potential process of local adaptation of the populations to the different environmental conditions associated to elevational variation between sites (e.g. water temperature, water flow velocity, UV, oxygen concentration). E. latifolium did not show significant genetic differentiation in the other barrier types of reservoir dam and intermittent flow. It suggests that E. latifolium adults fly over the small-size reservoir dam that we studied (< 0.5 km2) and have adapted life history strategy to migrate across the intermittent sections.