目标:雄激素,男性和雌雄同体的同时出现,是一种罕见的生殖系统。如果男性比雌雄同体受益于更高的男性适应性,则可以维持男性,被称为男性优势。由于资源的重新分配,生育率的增加可以带来男性优势。然而,实证研究通常比较一个开花季节的性表型,因此忽略了多年生植物连续季节的潜在累积效应。在这项研究中,我们量化了男性生育优势的各个组成部分,在季节内和季节之间,在长寿的多年生灌木Phillyreaangustifolia(木脂科)中。虽然,由于特殊的二等位基因自交不亲和系统和女性不育突变与不亲和的崩溃严格相关,雄性不需要生育优势来坚持这个物种,这一优势仍然是其平衡频率的重要决定因素。
方法:对>1000个全同胞植物的调查使我们能够比较雄性和雌雄同体的雄性生育力的几个组成部分。对个体进行了花粉产生和营养生长的代表特征。通过分析母系后代,我们比较了男性和雌雄同体的成功。最后,使用我们评估的多状态捕获-再捕获模型,对于每一个性行为,一年的开花强度如何影响明年的生长和繁殖。
结果:雄性受益于更大的营养生长和开花强度。在一个季节内,雄性的种子是等距的两倍,兼容雌雄同体的竞争对手。此外,雄性更经常连续几年保持强烈的开花。最后,在雌雄同体的两个不相容群体之间,对男性生殖功能的投资似乎有所不同。
结论:男性,通过节省雌性繁殖的成本,有更高的开花频率和营养生长,两者都有助于男性在个人一生中的优势。这表明,仅在单个生殖期分析性表型的研究可能无法充分估计多年生植物的男性优势。
OBJECTIVE: Androdioecy, the co-occurrence of males and hermaphrodites, is a rare reproductive system. Males can be maintained if they benefit from a higher male fitness than hermaphrodites, referred to as male advantage. Male advantage can emerge from increased fertility owing to resource reallocation. However, empirical studies usually compare sexual phenotypes over a single flowering season, thus ignoring potential cumulative effects over successive seasons in perennials. In this study, we quantify various components of male fertility advantage, both within and between seasons, in the long-lived perennial shrub Phillyrea angustifolia (Oleaceae). Although, owing to a peculiar diallelic self-incompatibility system and female sterility mutation strictly associated with a breakdown of incompatibility, males do not need fertility advantage to persist in this species, this advantage remains an important determinant of their equilibrium frequency.
METHODS: A survey of >1000 full-sib plants allowed us to compare males and hermaphrodites for several components of male fertility. Individuals were characterized for proxies of pollen production and vegetative growth. By analysing maternal progeny, we compared the siring success of males and hermaphrodites. Finally, using a multistate capture-recapture model we assessed, for each sexual morph, how the intensity of flowering in one year impacts next-year growth and reproduction.
RESULTS: Males benefitted from a greater vegetative growth and flowering intensity. Within one season, males sired twice as many seeds as equidistant, compatible hermaphroditic competitors. In addition, males more often maintained intense flowering over successive years. Finally, investment in male reproductive function appeared to differ between the two incompatibility groups of hermaphrodites.
CONCLUSIONS: Males, by sparing the cost of female reproduction, have a higher flowering frequency and vegetative growth, both of which contribute to male advantage over an individual lifetime. This suggests that studies analysing sexual phenotypes during only single reproductive periods are likely to provide inadequate estimates of male advantage in perennials.