Maggie Triska, 2005

Viterbo University

Sexual Success of Isolated Clonal Plant Populations

Sexual reproduction within self-incompatible plants requires that pollen be dispersed far enough to reach a compatible stigma of the same species. Plants depend on foraging pollinators to increase pollen dispersal. However, the distance that a pollinator is willing to forage should be related to resource availability, energy required, and type (generalist or specialist). This study examined how the foraging patterns of generalist and specialist pollinators interacts with the genetic isolation of clonal plant populations to limit or promote the sexual reproductive success of that plant. To test this Physalis subglabrata was planted in five plots, with four isolated populations in each. The populations consisted of plants representing a single clone or mixed clone in order to establish an isolation gradient from outcross pollen ranging from <1m to >100m for small plant populations. Fruit initiation, pollen dispersal, and type of pollinators, was recorded and analyzed. I hypothesized that distance to outcross pollen would limit fruit initiation; however, this proved to be insignificant (p=0.463). Visitation rate (bees/min) was the main factor contributing to the sexual success of Physalis (p=0.011). As expected, specialist bees were more frequent visitors at the species level and more faithful visitors at the individual level than generalist bees (p=0.004). Movement within plots, determined using fluorescent powder, varied between plots. One plot showed no powder movement among subplots, while, at the opposite extreme another plot showed powder movement of at least 25m in 62.5% of its flowers.


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