Outcrossing and Fecundity in the Woodland Sedge, Carex pensylvanica: Implications for Ecological Restoration

Abstract

The growing field of ecological restoration has prompted the horticulture industry to include a specialty niche of growers who breed native plants for restoration projects. The goals of native plant production are different than those of traditional horticulture, and native plant growers face a host of economic and technical challenges. Such challenges can limit their ability to produce adequate quantities and diversity of plants, and many ecologically important species are often underrepresented in restoration plantings. An example of this is the woodland sedge Carex pensylvanica -- an herbaceous-layer dominant in dry eastern forests -- which is marked by poor seed yield and germination rates, and is, as such, difficult to produce from seed. C. pensylvanica is self-compatible, and because of its expansive, clonal growth form, it is possible that long-term, self-pollination in many wild populations has resulted in inbreeding depression and reduced seed production and fitness. I tested this hypothesis in a greenhouse experiment where I controlled the breeding system of C. pensylvanica through hand-pollination to compare the reproductive output between outcrossed and self-pollinated manipulations. Results showed no effects of the breeding system manipulation on seed weight, but seed set in outcrossed plants was significantly higher (1.6x) than seed set in self-pollinated subjects. Based on this data, I developed models that predicted outcrossing seed set at 4.692 seeds/flower while selfing seed set predicted at 2.835 seeds/flower, supporting the hypothesis that long-term selfing is a significant contributor to the low seed production in this species. This study demonstrates that manipulating the breeding system of C. pensylvanica to achieve increased outcrossing is an effective way to increase seed production.