Pollinators play key roles in the reproduction of most angiosperms. Their ability to transport pollen from one individual to another largely determines which plants are able to pass on their genetic information to the next generation. The reproductive fitness of plants can be split into male and female fitness. Most studies focus on female fitness, which is often measured by determining how many ovules are successfully fertilized. Male fitness is understudied, but makes up half of a hermaphroditic plant’s reproductive fitness. This study aimed to investigate how different floral bee visitors influence the male fitness of the prairie plant Echinacea angustifolia. In a Minnesotan prairie restoration, we observed single flower visits by solitary bee taxa and then in the lab quantified the pollen removal for each visit. We only allowed certain pollinators to visit a given plant. On another set of flowering Echinacea plants, we only allowed a single bee taxon to visit a given plant. We then germinated, tissue-sampled, and extracted DNA from the resulting offspring. Next, we performed fragment analysis using 10 microsatellite primers on each individual and compared the results from this with the preexisting genetic information on the parental plants.
Results/Conclusions
We found that the solitary specialist bee, Andrena helianthiformis, removed significantly more pollen per visit than any other flower visitors. We also found that A. helianthiformis have a higher visitation rate than other flower visitors. Preliminary results indicate that a visit by A. helianthiformis also increased a plant’s male fitness, ability to sire seeds on other plants, compared to visits by other solitary bee species. Our results support previous work in this system that found A. helianthiformis significantly increased a plant’s female fitness. Taken together, we conclude that the presence of A. helianthiformis is an important predictor of Echinacea’s reproductive success. We also believe that our results help explain why small isolated populations of Echinacea, where A. helianthiformis is not present, have increased pollen limitation. Based on these results, future researchers can create more effective conservation and restoration plans for Echinacea and its specialist bee pollinator.