Crants, James , Rathcke, Beverly .
Floral neighborhood and pollination success in mayapple (Podophyllum peltatum L), a nectarless herb said to deceive its pollinators.
Mayapple (Podophyllum peltatum L.), an herb of Eastern North American deciduous forests, depends on outcross pollination by insects for sexual reproduction. However, its flowers lack nectar, for which its pollinators forage, and it consequently has very low visitation and pollination success. Species with rewarding flowers are known to increase the visitation rate and pollination success of nearby unrewarding species, including mayapple. In this study, we tested whether seven common species of co-flowering neighbors, including mayapple itself, facilitated mayapple pollination.
We measured pollination limitation by comparing the fruit and seed set of flowers receiving supplemental outcross pollination by hand with those of unmanipulated controls in the same patches. We tested for pollination facilitation by finding whether pollination limitation of reproductive success correlated with the number of neighboring flowers of each species. To determine whether heterospecific pollen interfered with ovule fertilization, we compared the reproductive success of flowers hand-pollinated with heterospecific pollen followed by outcross conspecific pollen with that of flowers pollinated with conspecific pollen only.
Visitation was too rare for analysis. Pollen deposition greatly limited fruit and seed production. However, we found little evidence for facilitation of mayapple pollination by any species, while several species appeared to compete with mayapple for resources other than pollination service. Fruit and seed set were unaffected by heterospecific pollen, suggesting that the lack of facilitation was not due to a trade-off between the positive effects of increased visitation and the negative effects of increased heterospecific pollen receipt.
Mayapple probably interacts with pollinators too rarely to have detectable pollinator-mediated interactions with other plants in our system. Lacking the targeted pollen dispersal common to many other deceit-pollinated plants, mayapple may lose too much pollen to its neighbors to experience strong facilitation in most habitats.
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1 - University of Michigan, Department of Ecology & Evolutionary Biology, 830 North University Avenue, Ann Arbor, Michigan, 48109-1048, USA
Presentation Type: Oral Paper:Papers for Topics
Location: Lake Ontario/Hilton
Date: Tuesday, July 10th, 2007
Time: 10:15 AM