Spring wildflowers in North American forests are declining as human disturbances degrade and fragment habitats. Many spring ephemerals are self-incompatible and rely on insects for pollination. These traits could be an important factor in their persistence in fragmented landscapes. Low reproductive output has been shown in small, isolated populations of plants, and spring wildflowers in forest fragments may show a similar pattern. Possible causes for low fecundity could be insufficient pollinator service and limited mate availability for self-incompatible plants. Delphinium tricorne, Dicentra cucullaria and Cardamine concatenata are three self-incompatible spring wildflowers of North America. This project will attempt to answer the following questions: 1) Does forest fragment size affect the reproductive success of Delphinium tricorne, Dicentra cucullaria, and Cardamine concatenata? 2) Does population density of Delphinium tricorne, Dicentra cucullaria, and Cardamine concatenata affect reproductive success? 3) Does bumblebee abundance and diversity differ among forest fragments of different sizes? 4) Are differences in bumblebee abundance and diversity related to fecundity of Delphinium tricorne, Dicentra cucullaria, and Cardamine concatenata in fragmented populations? Ten sites for Cardamine concatenata and six sites for Delphinium tricorne were used to examine reproductive success of wild populations. Forested areas were selected based on the size of the forest fragment and measured using Google Earth and Image J 1.41. The field study will be repeated for Dicentra cucullaria and Delphinium tricorne in spring 2010. Twenty plants were flagged at each site and the number of flowers was recorded. Flowering plant density was measured in a 10 x 10 meter plot to compare differences between populations. The plants were naturally pollinated and allowed to set seed. All maturing seedpods were collected and the number of seeds was recorded for each site. Pollinators were surveyed with colored pan traps.
Results/Conclusions
Preliminary results suggest significant differences in mean flowering plant densities and in mean seed production between sites for the Cardamine and Delphinium. Linear regression analysis showed a positive relation between forest fragment size and plant density for both species. No significant relationship was found between average seed production and plant density or forest fragment size. However, Delphinium did seem to have a positive linear relationship between average seed production and both fragment area and plant density. Bumblebee data was inadequate for analysis. Further sampling may strengthen the results of this study and the addition of pollinator data may resolve the issue of low reproductive output and inadequate pollinator service.
