Sexual conflict over pollination-induced floral closure in a gynodioecious herb

<jats:p>Pollination-triggered floral closure is traditionally interpreted as an adaptive maternal strategy to reallocate resources toward fruit and seed development. Yet premature pollination-induced floral closure under severe pollen limitation contradicts the female-function framework, indicating that pollen donors induce early floral closure and that fitness optima diverge between pollen donors and recipients would impose fitness costs on maternal plants, resulting in interlocus sexual conflict over floral longevity. Here, we test the male-manipulation hypothesis in natural populations of the gynodioecious herb &lt;i&gt;Cyananthus delavayi&lt;/i&gt;. We first investigated whether pollen deposition can trigger closure by experimentally blocking fertilization through style removal and by manipulating pollen load. We then compared seed set and seed quality in flowers subjected to different pollen loads and donor numbers. Pollination can induce floral closure even when ovule fertilization is fully prevented through style removal or heterospecific pollination. Closure time decreased with larger pollen loads in both sex morphs, and mostly occurs before pollen reaches the ovary when saturating pollinated. Seed set increased with increasing pollen load and supplemental pollination, but a larger pollen load with one-donor pollination did not enhance seed quality. Compared to one-donor pollination, two-donor pollination produced larger seeds and improved seed germination, especially under saturating pollen availability. Our results demonstrate that pollen-driven premature closure imposes measurable maternal fitness costs under natural pollen limitation, documenting interlocus sexual conflict over floral longevity in &lt;i&gt;C. delavayi&lt;/i&gt;. This study challenges the traditional view that plastic floral longevity evolves via a balance between pollinator attraction and maintenance cost. Instead, it adds to a growing body of evidence that sexual selection is a significant force shaping plant reproductive trait evolution, extending the scope of plant sexual selection theory.</jats:p>