Abstract
Reservoir obstructs gene flow of stream invertebrates along a channel, which takes place via larval drift and adult flight. It may result in genetic differentiation between above and below reservoir, which would reduce genetic diversities in fragments. Gene flow across a reservoir may be more strongly obstructed if the area of standing water is larger. Using RAPD, we investigated the genetic structure of Stenopsyche marmorata populations found above and below the reservoir, and the reference stream of 6 reservoirs in small to large water surface area. As a result, out of the 6 reservoirs, significant genetic differentiations were detected in the biggest 2 reservoirs with an area of standing water larger than 3.27 km2. However, these genetic differentiations did not result in the reduction of genetic diversities in the fragments.
