Data from: Testing models of sex ratio evolution in a gynodioecious plant: female frequency covaries with the cost of male fertility restoration

In many gynodioecious species, cytoplasmic male sterility genes (CMS) and nuclear male fertility restorers (Rf) jointly determine whether a plant is female or hermaphrodite. Equilibrium models of cytonuclear gynodioecy, which describe the effect of natural selection within populations on the sex ratio, predict that the frequency of females in a population will primarily depend on the cost of male fertility restoration, a negative pleiotropic effect of Rf alleles on hermaphrodite fitness. Specifically, when the cost of restoration is higher, the frequency of females at equilibrium is predicted to be higher. To test this prediction, we estimated variation in the cost of restoration across 26 populations of Lobelia siphilitica, a species in which Rf alleles can have negative pleiotropic effects on pollen viability. We found that L. siphilitica populations with many females were more likely to contain hermaphrodites with low pollen viability. This is consistent with the prediction that the cost of restoration is a key determinant of variation in female frequency. Our results suggest that equilibrium models can explain variation in sex ratio among natural populations of gynodioecious species.

在众多雌全异株物种中，细胞质雄性不育基因（cytoplasmic male sterility genes，CMS）与核雄性育性恢复基因（nuclear male fertility restorers，Rf）共同决定植株的性别为雌性或雌雄同株。针对核质互作雌全异株的平衡模型，通过阐释种群内自然选择对性比的调控效应，预测种群内雌性频率主要取决于雄性育性恢复的代价——即Rf等位基因对雌雄同株适合度的负多效性效应。具体而言，恢复代价越高，平衡状态下种群的雌性频率便越高。
为验证这一预测，我们对26个山梗菜（Lobelia siphilitica）种群的恢复代价变异进行了评估；该物种的Rf等位基因可对花粉活力产生负多效性影响。研究发现，雌性个体占比较高的L. siphilitica种群，其雌雄同株个体更大概率表现出较低的花粉活力。这一结果与“恢复代价是雌性频率变异的关键决定因素”的预测相符。本研究结果表明，平衡模型能够解释雌全异株物种自然种群间的性比变异。