Wang Juan, Zhang Chunyu, Zhao Xiuhai, Gadow Klaus V
Key Laboratory for Forest Resources and Ecosystem Processes of Beijing, Beijing Forestry University, Beijing, China.
PLoS One. 2013 Dec 6;8(12):e81140. doi: 10.1371/journal.pone.0081140. eCollection 2013.
The reproductive success of a female plant in a dioecious species may be affected by pollen limitation and resource limitation. This study presents evidence that the reproductive success of the dioecious understorey tree species, Rhamnus davurica, is affected by the distance to the nearest male. The sex ratios were female-biased, although showing fluctuations in the three years of conducting the study. The mortality rate of females was higher than that of males indicating a trade-off between reproduction and survival. Altogether 49 females, designated as "focal females", were randomly selected for monitoring their reproductive status between April and October in 2010. But successful reproduction (meaning that the flowering female trees had fruit in the fruiting season) was observed only in 28 females in 2011 and 16 females in 2012. The method of path analysis was applied to determine the effect of topography, local competition and proximity to the nearest male on the fruit set of the females. In the three years of the study, elevation, competition and female size had no significant effect on the fruit set. The distance to the nearest male, however, had a significant effect on fruit set. Number of fruits and fruit set were decreased with increasing distance to the nearest male. It was possible to estimate maximum fruit set, based on the comparatively large dataset. The number of fruits and the fruit set are exponentially related to the distance to the nearest male and the relationships are described by an exponential model. The results of this study support the importance of pollen limitation on the reproductive success in Rhamnus davurica.
在雌雄异株物种中，雌性植株的繁殖成功率可能会受到花粉限制和资源限制的影响。本研究提供了证据表明，雌雄异株的林下树种鼠李的繁殖成功率受到与最近雄株距离的影响。性别比例偏向雌性，尽管在开展研究的三年中呈现出波动。雌性的死亡率高于雄性，这表明在繁殖和生存之间存在权衡。2010年4月至10月期间，总共随机选择了49株雌性植株，指定为“焦点雌株”，以监测它们的繁殖状况。但在2011年仅观察到28株雌株成功繁殖（即开花的雌树在结果季节有果实），2012年为16株。采用通径分析方法来确定地形、局部竞争以及与最近雄株的距离对雌株坐果的影响。在研究的三年中，海拔、竞争和雌株大小对坐果没有显著影响。然而，与最近雄株的距离对坐果有显著影响。果实数量和坐果率随着与最近雄株距离的增加而降低。基于相对较大的数据集，有可能估算出最大坐果率。果实数量和坐果率与到最近雄株的距离呈指数关系，这些关系由一个指数模型来描述。本研究结果支持了花粉限制对鼠李繁殖成功的重要性。
