Geographical variation in autonomous self-pollination levels unrelated to pollinator service in Helleborus foetidus (Ranunculaceae)

Autonomous self-pollination may be considered as a mechanism enhancing plan t reproductive success when plant access to pollen sources may limit seed p roduction. We have studied the relationship between geographical patterns o f variation in pollinator service to Helleborus foetidus and self-pollinati on ability in three widely spaced regions in the Iberian Peninsula. As coul d be expected from its early flowering period, pollinator visitation rates to both plants and flowers of H. foetidus were very low at all sites. Polli nator composition remained consistent among regions, but there was signific ant variation among regions in pollinator service. Despite the low visitati on rates, fruit set did not appear to be pollen limited in any of the study areas, which may be explained by the long duration of flowers (up to 20 d) . When pollinators were excluded experimentally, fruit set decreased signif icantly, but substantial levels of self-pollination occurred at all regions . Autonomous self-pollination levels were lowest in the two regions with lo west pollinator service and highest in the region with highest pollinator s ervice. This disagreement between our results and the expectations derived from the reproductive assurance hypothesis may reflect a nonequilibrium sit uation of the northern H. foetidus populations in relation to their current pollinating environment.