PARENT SESSION
Poster Session #37: Plant Ecology: Populations.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Fire and its role in metapopulation dynamics of turkeybeard (Xerophyllum asphodeloides), a rare forest herb.

Bourg, Norman^*,1,2, Gill, Douglas¹, McShea, William², Kress, John³, ¹ University of Maryland-College Park, College Park, MD² Conservation and Research Center, Front Royal, VA³ National Museum of Natural History, Washington, DC

ABSTRACT- We undertook a three-pronged approach to study the population biology of turkeybeard (Xerophyllum asphodeloides), a rare lily associated with southern Appalachian pine-oak forests, and fire's role as a mediating factor in population maintenance and spatial distribution. X. asphodeloides is endangered or rare in portions of its range, listed as a sensitive species on National Forest lands, and is included in the Center for Plant Conservation's National Collection of Endangered Plants. It is also thought to be fire-adapted; yet, there has been no experimentally validated ecological linkage to fire. We performed a fire/canopy manipulation field experiment on a marked long-term study population to determine the impact of these factors on survival and reproduction. An immense flowering response to our treatments occurred in the second and third post-manipulation years, with many plants reproducing for the first time, and analysis of long-term data showed that this response was not due to cyclic flowering. Mixed-model ANCOVA analyses yielded significant positive effects of both fire and canopy alteration on the number of fruits and seeds. Inflorescences from another nearby undisturbed population showed virtually no fruit or seed production. A pollination experiment conducted on 21 virgin inflorescences showed that outcrossed flowers produced significantly more seed than selfed. Analyses of genetic variation for 13 allozyme loci in 12 populations support a metapopulation view of patchy populations connected by limited gene flow within the forest matrix. Finally, survey data from 26 populations were combined in a GIS with 8 environmental data layers to build a model for predicting turkeybeard occurrence and habitat on the landscape. The results support the hypothesis that fire stimulates mass flowering in X. asphodeloides, thereby creating opportunity for outcrossing to enhance genetic exchange within and among local populations. These findings have implications for the study of metapopulations and disturbance regimes in Appalachian forests.

KEY WORDS: fire ecology, metapopulations, genetic structure, GIS models