Vamosi Jana C, Otto Sarah P
Department of Zoology, University of British Columbia, 6270 University Boulevard, Vancouver, Canada V6T 1Z4.
Proc Biol Sci. 2002 Jun 7;269(1496):1187-94. doi: 10.1098/rspb.2002.2004.
Dioecious plants (with separate male and female individuals) more often have drab, inconspicuous flowers than related bisexual plants. Models indicate, however, that similar conditions favour the evolution of showy floral displays in dioecious and bisexual plants. One difference, however, is that dioecious plants may evolve floral displays that are sexually dimorphic. We show that males are more likely to evolve showy flowers than females in animal-pollinated plants, especially when pollinators are abundant. We demonstrate that this dimorphism places showy dioecious plants at a much higher risk of extinction during years of low pollinator abundance because pollinators may fail to visit female flowers. The higher extinction risk of showy dioecious plants provides an explanation for the fact that dioecious plants that do persist tend to have inconspicuous flowers and are more often wind pollinated. It may also help explain why dioecious plants are less species-rich than related bisexual plants.
雌雄异株植物（具有单独的雄性和雌性个体）通常比相关的两性植物拥有更为单调、不显眼的花朵。然而，模型表明，相似的条件有利于雌雄异株植物和两性植物中艳丽花朵展示的进化。不过，一个差异在于，雌雄异株植物可能进化出具有性别二态性的花朵展示。我们发现，在动物传粉的植物中，雄性比雌性更有可能进化出艳丽的花朵，尤其是在传粉者丰富的时候。我们证明，这种二态性使得艳丽的雌雄异株植物在传粉者数量稀少的年份面临更高的灭绝风险，因为传粉者可能不会光顾雌花。艳丽的雌雄异株植物较高的灭绝风险解释了这样一个事实：持续存在的雌雄异株植物往往花朵不显眼，且更多是风媒传粉。这也可能有助于解释为什么雌雄异株植物的物种丰富度低于相关的两性植物。
