XVI International Botanical Congess

Extinction risks vary among subpopulations, often as a function of their size or extent. Over 8 years, I followed the fates of >200 subpopulations of the annual plant, Clarkia concinna (Onagraceae). Extinction rates are highest in small, isolated subpopulations, due to apparent Allee effects and to abiotic disturbances (landslides). Using manipulative field experiments I found that small patches experience reproductive failure due to lack of effective pollination when patches are too isolation. In contrast, sufficiently large patches attract pollinators regardless of their degree of isolation. Although subpopulation extinctions are common in this system, due to the longevity of most populations, it is unclear how these extinctions will affect persistence of the metapopulation as a whole. However, in one isolated region an entire metapopulation may be headed towards extinction.