Vamosi Jana C, Vamosi Steven M, Barrett Spencer C H
Department of Biological Sciences, University of Calgary, Canada.
Proc Biol Sci. 2006 Sep 22;273(1599):2401-7. doi: 10.1098/rspb.2006.3599.
The flowers and inflorescences of animal-pollinated dioecious plants are generally small and inconspicuous in comparison with outcrossing cosexual species. The net benefits of an attractive floral display may be different for dioecious compared to cosexual populations because dioecious species experience a more severe reduction in pollen delivery when pollinators forage longer on fewer individuals. Here, we develop a model that predicts the decrease in pollen delivery in dioecious relative to cosexual populations from female-female, female-male and male-male visit sequences as the number of individuals visited varies. To evaluate the predictions of our model we conducted a common garden experiment with dioecious and monoecious (cosexual) arrays of the insect-pollinated herb Sagittaria latifolia. We find that, although increasing the advertisements of floral rewards (i.e. increasing floral display) attracts more pollinators to individuals, the probability that these pollinators subsequently deliver pollen to neighbouring plants depends on sexual system. Because the number of individual plants visited per foraging trip did not increase significantly with floral display, the relative pollination success of dioecious versus monoecious populations decreases with increased floral display. We propose that this could explain why dioecy is strongly correlated with reduced floral display among angiosperm species.
与异花授粉的两性花植物相比，动物授粉的雌雄异株植物的花朵和花序通常较小且不显眼。与两性花种群相比，有吸引力的花展示对雌雄异株植物的净收益可能不同，因为当传粉者在较少个体上觅食时间更长时，雌雄异株物种的花粉传递会经历更严重的减少。在这里，我们建立了一个模型，该模型预测随着被访问个体数量的变化，从雌-雌、雌-雄和雄-雄访问序列来看，雌雄异株相对于两性花种群的花粉传递减少情况。为了评估我们模型的预测，我们对虫媒传粉草本植物宽叶慈姑的雌雄异株和雌雄同株（两性花）阵列进行了一个共同花园实验。我们发现，虽然增加花的报酬广告（即增加花展示）会吸引更多传粉者到个体上，但这些传粉者随后将花粉传递到相邻植物的概率取决于性系统。由于每次觅食行程中被访问的个体植物数量并没有随着花展示的增加而显著增加，雌雄异株种群相对于雌雄同株种群的相对授粉成功率随着花展示的增加而降低。我们提出，这可以解释为什么在被子植物物种中，雌雄异株与减少的花展示密切相关。
