As with newly formed oceanic islands, new volcanic areas on continents also provide an opportunity to examine populational phenomena during arrival and early establishment of plant species. Of special interest is the degree of genetic variance in these early colonizers, as they contain genetic resources that fuel, in part, future populational differentiation and eventual speciation. It is predicted that new populations in open ash fields should (1) result from limited numbers of propagules from geographically adjacent areas, and (2) contain reduced genetic variation in comparison with source populations. Hypochaeris tenuifolia (Asteraceae), confined to high elevation volcanic peaks (1750-2400m) along the southern Andes between 35-39 degrees S, was selected to test these predictions. A new volcanic cone, La Navidad, erupted on the flank of Volcan Lonquimay, Chile, on 25 Dec 1988, spreading lava and ash along well documented routes. During 1999 and 2000, we analyzed using AFLP markers 11 populations (20-30 plants in each) of H. tenuifolia in two transects on Volcan Lonquimay, including newly ashed slopes and undisturbed Auraucaria forests, and compared these data with those from 30 additional populations throughout the range of the species. The results show a surprisingly high level of genetic variance in pioneer populations as well as connections to many different source areas. It appears that biological attributes of species, in this case dispersal capability, can be more important than biogeographic parsimony in defining genetic characteristics of colonizing species in island-like habitats.

Key words: AFLP, biogeography, Chile, genetic variation, Hypochaeris, volcanoes