Outcrossing and fecundity in the woodland sedge Carex pensylvanica: implications for ecological restoration

Native plant growers face a host of economic and technical challenges that 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 Lam. (Cyperaceae)—a 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. It is possible that long-term, self-pollination in many wild populations has resulted in inbreeding depression and reduced seed production and fitness. I test this hypothesis in a greenhouse experiment in which I control the breeding system of C. pensylvanica through hand-pollination to compare the reproductive output between outcrossed and self-pollinated manipulations. Results show no effect of the breeding system manipulation on seed weight, but seed set in outcrossed plants was significantly higher than seed set in self-pollinated subjects. Based on these data, I developed models that predicted outcrossing seed set at 4.6 seeds/inflorescence selfing seed set predicted 2.8 seeds/inflorescence, 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, which in turn would allow growers to increase the availability of plants for restoration projects.