Data from: The evolution of males: support for predictions from sex allocation theory using mating arrays of Sagittaria latifolia (Alismataceae)

Investment in male function should often yield diminishing fitness
returns, subjecting the evolution of male phenotypes to substantial
constraints. In plants, the subdivision of male function via the gradual
presentation of pollen might minimize these constraints by preventing the
saturation of receptive stigmas. Here we report on an investigation of (a)
patterns of investment in male function by plants in hermaphroditic
(monoecious) and dioecious populations of Sagittaria latifolia, and (b)
patterns of siring success by males vs. hermaphrodites in experimental
mating arrays. We show that in natural populations, males from dioecious
populations had greater investment in male function than hermaphrodites in
monoecious populations. However, as a proportion of total flower
production, males presented substantially fewer flowers at once than
hermaphrodites. In comparison with hermaphrodites, therefore, males
prolonged the period over which they presented pollen. In mating arrays
comprised of females, males, and hermaphrodites, siring success by males
increased linearly with flower production. This finding is consistent with
the existence of a linear gain curve for male function in S. latifolia and
supports the idea that the gradual deployment of male function enables
plants to avoid diminishing returns on the investment in male function.

雄性生殖功能的投入通常会产生适合度收益递减效应，对雄性表型的演化造成显著约束。在植物中，通过逐步散粉分次分配雄性生殖功能，可通过防止可授性柱头饱和，最大程度减轻这类限制。本研究针对两个方向展开调查：（1）宽叶慈姑（Sagittaria latifolia）的雌雄同株（单性同株）种群与雌雄异株种群中，植株对雄性生殖功能的投入模式；（2）实验交配群落中，雌雄异株种群的雄株与雌雄同株个体的父本繁殖成功率模式。研究结果显示，在自然种群中，雌雄异株种群的雄株对雄性生殖功能的投入高于雌雄同株种群的个体。但就总花量的占比而言，雄株单次开放的花朵数量显著少于雌雄同株个体。因此，相较于雌雄同株个体，雄株的花粉释放周期更长。在由雌株、雄株与雌雄同株个体组成的实验交配群落中，雄株的父本繁殖成功率随花量呈线性增长。该发现与宽叶慈姑雄性生殖功能存在线性收益曲线的结论相符，同时支持了‘逐步分配雄性生殖功能可使植物避免雄性生殖投入的适合度收益递减’这一观点。