Morgan Martin T
Department of Ecology and Evolution, The University of Chicago, 1101 East 57th Street, Chicago, IL, 60637, USA.
Evolution. 1992 Aug;46(4):1199-1213. doi: 10.1111/j.1558-5646.1992.tb00628.x.
Plant attributes serving both male and female sex functions are thought to favor hermaphroditic breeding systems over systems where sex expression is separated between individuals. Morphological features used by plants to attract biotic pollinators can be considered in this light, because such "attractive" structures are prerequisite for both pollen donation and receipt. A model involving allocation of a limiting resource between attractive structures benefiting both sex functions, structures benefiting male function only, and structures benefiting female function only, is constructed and analyzed using the evolutionary stable strategy (ESS) approach. Contrary to expectation, conditions resulting in large allocation to attractive structures tend to destabilize hermaphroditism, although the effect is slight. Substantial asymmetry in the benefits accruing to male and female fertility for a given investment in pollinator attraction produces more pronounced effects, reducing the parameter space in which hermaphroditism is expected. Results of this model are used to assess the importance of "accelerating gain" curves previously suggested for the evolution of dioecy in flowering plants. Accelerating gains associated with fruit production and dispersal represent female function only, and can be sufficient to initiate evolution toward dioecy. Accelerating gains associated with pollinator attraction may contribute to the evolution of separate sexes only if male function benefits from increased investment in attractive structures at a disproportionate rate compared to female function. Even in this instance, though, hermaphroditism may be evolutionarily stable.
兼具雄性和雌性功能的植物属性被认为有利于雌雄同体的繁殖系统，而非性别表达在个体间分离的系统。从这一角度来看，植物用于吸引生物传粉者的形态特征是可以考虑的，因为这种“吸引性”结构对于花粉的捐献和接受而言都是前提条件。构建了一个模型，该模型涉及在对两种性功能均有益的吸引性结构、仅对雄性功能有益的结构以及仅对雌性功能有益的结构之间分配一种有限资源，并使用进化稳定策略（ESS）方法进行分析。与预期相反，导致大量资源分配给吸引性结构的条件往往会破坏雌雄同体状态的稳定性，尽管这种影响很轻微。对于在传粉者吸引方面的给定投入，雄性和雌性育性所获得的益处存在显著不对称时，会产生更明显的影响，减少了预期出现雌雄同体状态的参数空间。该模型的结果用于评估先前提出的开花植物雌雄异株进化中“加速收益”曲线的重要性。与果实生产和传播相关的加速收益仅代表雌性功能，并且可能足以启动向雌雄异株的进化。与传粉者吸引相关的加速收益，只有在雄性功能从对吸引性结构的投入增加中获得的收益与雌性功能相比不成比例时，才可能有助于雌雄异株的进化。不过，即使在这种情况下，雌雄同体状态在进化上也可能是稳定的。
