GENE FLOW AMONG CONSPECIFIC POPULATIONS OF BAETIS SP (EPHEMEROPTERA) - ADULT FLIGHT AND LARVAL DRIFT

The genetic structure of populations of Baetis sp. (Ephemeroptera:Baet idae) was used to draw inferences about the means of dispersal within and between stream systems of the Conondale Range, Queensland, Austral ia. Allozyme electrophoresis was used to examine allelic frequencies a t five variable loci in geographically distant populations of nymphs i n the same drainage and in nearby populations in different drainages. The results showed widespread gene now between drainages and a tendenc y for local differentiation. We concluded that adult night represents an effective means for dispersal between drainage systems. The differe ntiation between populations at a local scale and erratic deviations f rom Hardy Weinberg equilibrium could have occurred if the nymphs colle cted from any stream were the offspring of only a few adults. If this is the case, the dispersal capabilities of nymphs by swimming, crawlin g or drift may be minimal even within a single stream.