EFFECT OF METAPOPULATION STRUCTURE ON NUCLEAR AND ORGANELLAR DNA VARIABILITY IN SEMIARID ENVIRONMENTS OF SOUTHERN AFRICA

The analysis of uniparentally inherited organellar DNA (such as mitoch ondrial DNA) has yielded a wealth of information about the population structures of Northern Hemisphere vertebrates. In southern Africa, how ever, several species show little or no variability in organellar DNA, yet show high levels of variability in nuclear DNA as measured with a llozyme electrophoresis. To understand this difference, we used Monte Carlo methods to simulate the effects of subpopulation extinction and recolonization on the loss of variability in organellar and nuclear DN A for both the island and stepping-stone models of migration. We found that with nearly all combinations of extinction and recolonization th ere was a significantly greater loss of variability in organellar DNA than in nuclear DNA. The implications of this study are (1) that molec ular methods measuring genetic variability in nuclear DNA must be used to study the population genetics of most animals in southern Africa a nd (2) that population extinction and recolonization appear to play a larger role in southern African populations than in Northern Hemispher ic populations.