Contribution of delayed autonomous selfing to reproductive success in Mountain Laurel, Kalmia latifolia (Ericaceae)

The release of anthers held under tension which catapult pollen onto the stigma near the end of floral life has been proposed as a mechanism for autonomous self-fertilization in normally outcrossing Kalmia latifolia. We examined the importance of this delayed autonomous self-pollination to fruit production and the efficiency of the pollen deposition mechanism under field conditions. By comparing intact open-pollinated flowers with emasculated flowers we found that autonomous self-pollination did not increase fruit production. To evaluate the efficiency of the catapult mechanism of selfing, we compared the relative fruit production of flowers that were hand-pollinated with self-pollen with those that self-pollinated spontaneously. Fruit set was higher in hand-selfed flowers than in the autonomously-selfed flowers, indicating that the natural mechanism of selfing is inefficient. Through the observation of flowers protected from pollinators we determined the natural pattern of floral phenology and anther release. The effect of timing of autonomous selfing on fruit production was assessed by manipulating the time of anther release. The timing of selfing is not related to fruit production and varies widely among flowers. Although autonomous selfing did not contribute to fruit production under natural conditions, it can assure reproduction in the absence of pollinators.