PARENT SESSION
Poster Session #50: Evolutionary Ecology.
Friday, August 10, 2001. Presentation from 10:30 AM to 12:00 PM. Exhibition Hall
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The effect of variation in floral reproductive morphology on pollen dispersal and gene flow in Mimulus ringens.
Holmquist, Karsten1, Karron, Jeffrey1, Mitchell, Randall2, 1 2
ABSTRACT- Animal mediated pollen dispersal has traditionally been viewed as single, completely mixed pools of pollen from which no loss occurs, so that the entire load experiences a fixed rate of decay. The predictions of Bateman's 1947 model underestimate initial, and overestimate tail transition probabilities. In 1998, Harder and Wilson proposed three models in which the interactions between the vector, floral reproductive organs, and the transported pollen load cause portions of the pollen to experience differential transport conditions. These variable conditions may lead to differential transition probabilities between donor specific loads and receptive stigmas in the foraging sequence. Linear arrays of Mimulus ringens were grown in order to determine patterns of pollen carryover for three sympatric species of Bombus vectors. Each array was comprised of palindromic sequences of singly rametted genets, the first genet being labeled with fluorescent pollen analogs. Pollen carryover from a total of 6 unique donor genets was quantified by counting the number of dye particles on each of up to 26 receptive stigmas over 20 runs. There was considerable carryover with a mean transport distance of 17.4 flowers. The mean pollen decay rate was 0.039, according to a single geometric model. Mean transport distance was highly positively correlated with initial deposition, which was highly negatively correlated with anther-stigma separation. Marked variation was detected for all carryover characteristics between pollen donors and pollinator identity.
KEY WORDS: Mimulus ringens, pollen carryover, gene flow, pollination