Wu Ling-Yun, Huang Shuang-Quan, Tong Ze-Yu
Faculty of Resources and Environmental Science, Hubei University, Wuhan 430062, China.
Institute of Evolution and Ecology, School of Life Sciences, Central China Normal University, Wuhan 430079, China.
Plant Divers. 2023 Oct 19;46(5):661-670. doi: 10.1016/j.pld.2023.10.001. eCollection 2024 Sep.
Reproductive strategies of sexually dimorphic plants vary in response to the environment. Here, we ask whether the sexual systems of species (i.e., selfing homostylous and out-crossing distylous) represent distinct adaptive strategies to increase reproductive success in changing alpine environments. To answer this question, we determined how spatial and temporal factors (e.g., elevation and peak flowering time) affect reproductive success (i.e., stigmatic pollen load) in nine wild species (seven distylous and two homostylous) among 28 populations along an elevation gradient of 1299-3315 m in the Hengduan Mountains, southwestern China. We also observed pollinators and conducted hundreds of hand pollinations to investigate inter/intra-morph compatibility, self-compatibility and pollen limitation in four species (two distylous and two homostylous). We found that species at higher elevation generally had bigger flowers and more stigmatic pollen loads; late-flowering individuals had smaller flowers and lower pollen deposition. Stigmatic pollen deposition was more variable in distylous species than in homostylous species. Although seed set was not pollen-limited in all species, we found that fruit set was much lower in distylous species, which rely on frequent pollinator visits, than in homostylous species capable of autonomous self-pollination. Our findings that pollination success increases at high elevations and decreases during the flowering season suggest that distylous and homostylous species have spatially and temporally distinct reproductive strategies related to environment-dependent pollinator activity.
两性异株植物的繁殖策略会因环境而异。在此，我们探讨物种的性系统（即自交同型花柱和异交异型花柱）是否代表了在不断变化的高山环境中提高繁殖成功率的不同适应性策略。为回答这个问题，我们确定了空间和时间因素（如海拔和盛花期）如何影响中国西南部横断山脉海拔1299 - 3315米梯度上28个种群中9个野生种（7个异型花柱和2个同型花柱）的繁殖成功率（即柱头上的花粉负载量）。我们还观察了传粉者，并进行了数百次人工授粉，以研究四个物种（2个异型花柱和2个同型花柱）的种间/种内形态兼容性、自交兼容性和花粉限制情况。我们发现，海拔较高的物种通常花朵更大，柱头上的花粉负载量更多；开花较晚的个体花朵较小，花粉沉积量较低。异型花柱物种的柱头花粉沉积比同型花柱物种更具变异性。虽然并非所有物种的结实都受花粉限制，但我们发现，依赖传粉者频繁访问的异型花柱物种的坐果率远低于能够自主自花授粉的同型花柱物种。我们的研究结果表明，高海拔地区授粉成功率增加，花期授粉成功率降低，这表明异型花柱和同型花柱物种在空间和时间上具有与环境依赖型传粉者活动相关的不同繁殖策略。
