Bourg, Norman A. .
Pollination Biology of Turkeybeard (Xerophyllum asphodeloides) (L.) Nutt. (Melanthiaceae) in the Context of Fire in the Appalachian Mountains of Virginia, U.S.A.
XEROPHYLLUM asphodeloides is a rare, fire-adapted forest herb found primarily in the southern Appalachians and disjunctly in the New Jersey Pine Barrens. This species reproduces infrequently in undisturbed forest, but mass flowers following disturbance by fire and its associated canopy opening. The pollination biology of X. asphodeloides within the context of fire was studied through controlled hand pollination experiments and incidental pollinator observations and collections over three flowering seasons. Cerambycid beetles were the most diverse group of pollinators collected from inflorescences, followed by bees, which were also observed undertaking longer distance cross-pollinations between genets. Hand-pollinated outcross treatments produced consistently high levels of seed set/fruit, while open-pollinated natural controls exhibited considerably more inter-annual variability. Seed set in open-pollinated flowers was high and similar to hand-outcrossed flowers in fire-induced mass flowering years, but was low and similar to self-pollination treatments in years of sparse flowering. In concordance with a recent study of the congeneric beargrass (X. tenax), these results support the determination of a primarily outcrossing mating system with “leaky” self-incompatibility in X. asphodeloides, because of low but non-zero seed production occurring in self-pollinated flowers. Populations typically exhibit low flowering levels in undisturbed forest which in combination with their self-incompatibility subjects them to Allee effects due to pollinator limitation in most years. Disturbance by fire results in release from these limiting factors by inducing mass flowering and altering the forest habitat to increase insect pollinator activity, thus facilitating outcrossing and seed set in this rare species. In addition to providing valuable information on the breeding system of the only remaining unexamined species of Xerophyllum, the results of this study are important for conservation and management efforts because they have shown the importance of the interaction of disturbance by fire with insect-mediated outcrossing for successful seed production in X. asphodeloides.
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Mass flowering response of turkeybeard to wildlfire
Mass flowering response photos
1 - University of Maryland, Department of Biology, Biology Psychology Bldg, College Park, Maryland, 20742, USA
Presentation Type: Oral Paper:Papers for Topics
Date: Monday, July 31st, 2006
Time: 2:00 PM