Altered pollination ecology of a native plant species in the presence of an attractive non-native plant species.
Numerous plant species have been introduced to non-native environments across the globe. Daucus carota was introduced to North America from Europe. Its extensive presence on Nantucket, an island off the coast of Massachusetts, has been documented at least since the nineteenth century. To address whether the presence of D. carota affects the pollination of native species on Nantucket, we sought to answer three questions: (1) Does the presence of D. carota increase pollinator visits and diversity on Sericocarpus asteroides? (2) Does the removal of D. carota restore pollinator visits and diversities to those found in plots with only S. asteroides? and (3) Is there a relationship between the amount of heterospecific pollen and distance to the nearest D. carota population? To answer these questions, we determined that both species attract the same pollinators by first observing pollinator visits on D. carota, then performing the same observational study on S. asteroides. We recorded pollinator visitors in S. asteroides populations that were in allopatry and sympatry with D. carota. We followed this study with a manipulative experiment within sympatric plots in which we removed D. carota inflorescences and again recorded pollinator visits. In addition, we assayed S. asteroides inflorescences from a range of distances from D. carota for the presence of heterospecific pollen. Both species were generalist pollinated, and S. asteroides received more visits in the presence of D. carota. After the removal of D. carota inflorescences, the number and diversity of visitors declined. Finally, whereas populations of S. asteroides close to D. carota receive more overall pollen, there was no increase in heterospecific pollen.