Evol Ecol Res 9: 1245-1262 (2007) Full PDF if your library subscribes.
Empty flowers as a pollination-enhancement strategy
Susan F. Bailey, Anna L. Hargreaves, Sarah D. Hechtenthal, Robert A. Laird,* Tanya M. Latty, Tyler G. Reid, Andrew C. Teucher and Jeffrey R. Tindall
Department of Biological Sciences, University of Calgary, Calgary, Alberta T2N 1N4, Canada
Author to whom all correspondence should be addressed.
e-mail: rlaird@connect.carleton.caABSTRACT
Question: Can the reproductive benefits gained by mitigating the costs of self-pollination drive the evolution of nectarless flowers?
Features of model: Complementary analytical and simulation models determined the optimal proportion of nectarless flowers (‘nectar phenotype’) to maximize male reproductive success. Models considered a range of self-pollination costs and pollinator abundances. In the analytical model, equal numbers of each nectar phenotype were present. Pollinators used simple rules of behaviour, related to their current host plant’s perceived nectar status, to decide whether to stay on that plant or to move to a new plant. In the simulation model, pollinators used more sophisticated departure rules, comparing the current host plant’s perceived nectar status to the population mean. Plants with different proportions of nectarless flowers competed for successful pollination over multiple seasons.
Ranges of key variables: Relative cost of self-pollination (0.5–1); number of pollinators acting on a plant population per season (1–101); and proportion of nectarless flowers per plant (0–1).
Conclusions: Enhanced pollination success can drive the evolution of empty flowers in plants that are reliant on vector-mediated pollination. When the costs of selfing are low, an inflorescence with a low proportion of nectarless flowers is optimal, because pollination success is primarily determined by pollen removal. When the costs of selfing are high, an inflorescence with mostly nectarless flowers is optimal, because pollination success is primarily determined by outcrossing. Low pollinator abundances lead to a decreased optimal proportion of empty flowers to mitigate pollinator limitation.
Keywords: cross-pollination, geitonogamy, inbreeding depression, male function, nectar, nectarless flowers, outcrossing, reward, self-pollination.
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