Renosterbos is a shrub which is extremely common on the Cape coastal forelands. Together with several other fynbos species, it also occurs in isolated interior populations, confined to mesic high-altitude sites separated by large tracts of arid country. How did the outliers come to occupy such sites? Was fynbos previously more extensive, and is it currently in a contracted state due to widespread aridification since the last glacial maximum (vicariance hypothesis)? Or are the outliers the results of long-distance dispersal events (dispersal hypothesis)? These conflicting scenarios would produce different genetic signatures in extant populations, which should be detectable (in the absence of confounding factors such as subsequent gene flow) using highly polymorphic genetic markers. In the case of vicariance, long-isolated populations should have distinct genetic signatures and contain unique genotypes, and genetic difference should be correlated with duration of isolation. Neighbouring isolated populations would not necessarily be more closely related than very distant isolated populations. In the case of dispersal, colonies should consist of a subset of genotypes present in the founder population, and founder populations are likely to be those closest to colony populations. In this study we use three ISSR-PCR primers to survey the genomes of at least five individuals from each of ten populations across the entire species range, as a first step in constructing a phylogeographic hypothesis. The survey shows high levels of variation, most of which is partitioned among populations. Examination of geographic structuring in this variation may allow us to make inferences on population histories in renosterbos, which could be extrapolated to the history of fynbos as a whole.

Key words: fynbos, intraspecific variation, ISSR, phylogeography, population history