SPATIAL PATTERNS OF GENETIC-VARIATION GENERATED BY DIFFERENT FORMS OFDISPERSAL DURING RANGE EXPANSION

We examined the impact of three forms of dispersal, stepping-stone, no rmal and leptokurtic, on spatial genetic structure of expanding popula tions using computer simulations. When dispersal beyond neighbouring d emes is allowed, rare long-distance migration leads to the establishme nt of pocket populations in advance of the main invasion front and res ults in spatial clustering of genotypes which persists for hundreds of generations. Patchiness is more pronounced when dispersal is leptokur tic as is the case in many animal and plant species. These results are of particular interest because population genetic parameters such as gene flow and effective population size are commonly estimated using g ene frequency divergence information assuming equilibrium conditions a nd island models. We show how the three forms of dispersal during colo nization bring about contrasting population genetic structures and how this affects estimates of gene flow. The implications for experimenta l studies of the spatial dimension of population genetic structure are discussed.