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

Female reproductive biology of a facultative root hemiparasite, Castilleja linariifolia Benth. (Scrophulariaceae).

Cariveau, Daniel^*,1, Sevillano Garcia-Mayeya, Lucero², van der Ohe, Andrea², Brody, Alison³, Irwin, Rebecca⁴, ¹ Colorado State University, Fort Collins, Colorado² Rocky Mountain Biological Laboratory, Crested Butte, Colorado³ University of Vermont, Burlington, Vermont⁴ University of Georgia-Athens, Athens, Georgia

ABSTRACT- The fecundity of many hemiparasitic plants depends on at least two factors: resource uptake from their host plants and pollination success. Although numerous studies have examined the direct effects of host plant on hemiparasite success, very few studies have investigated the importance of variation in floral characters to pollination and reproductive success of these species. We conducted a two-year field study in which we examined pollen limitation and phenotypic variation of the hummingbird-pollinated, facultative root-hemiparasite Castilleja linariifolia Benth. (Scrophulariaceae). To determine if pollen deposition was limiting female reproductive success, we applied pollen to all flowers on randomly chosen treatment plants and left others to open, natural pollination. We then assessed proportion fruit production and total seed set for all plants. We found that pollen supplementation had a marginal positive effect on fruit set, but no significant effect on total seed set per plant, although the trend was of increasing seed set with pollen addition. To assess phenotypic variation, we measured 9 morphological characters and compared the magnitude of variation within and between field sites. In both years we saw high amounts of variation within and between sites for characters related to resource levels and low levels of variation in traits associated with pollinator attraction. Finally we used a path analysis to examine which characters may directly and indirectly influence the female reproductive success of this plant.

KEY WORDS: Castilleja linariifolia, hemiparastic plants, pollen limitation