College of Life Sciences, Zijingang Campus, Zhejiang University, Hangzhou, People's Republic of China.
PLoS One. 2011;6(8):e22903. doi: 10.1371/journal.pone.0022903. Epub 2011 Aug 4.
The Thousand-Island Lake region in Zhejiang Province, China is a highly fragmented landscape with a clear point-in-time of fragmentation as a result of flooding to form the reservoir. Islands in the artificial lake were surveyed to examine how population sex ratio of a dioecious plant specie Pistacia chinensis B. was affected by landscape fragmentation. A natural population on the mainland near the lake was also surveyed for comparison. Population size, sex ratio and diameter at breast height (DBH) of individuals were measured over 2 years. More than 1,500 individuals, distributed in 31 populations, were studied. Soil nitrogen in the different populations was measured to identify the relationship between sex ratio and micro-environmental conditions. In accordance with the results of many other reports on biased sex ratio in relation to environmental gradient, we found that poor soil nitrogen areas fostered male-biased populations. In addition, the degree of sex ratio bias increased with decreasing population size and population connectivity. The biased sex ratios were only found in younger individuals (less than 50 years old) in small populations, while a stable 1∶1 sex ratio was found in the large population on the mainland. We concluded that the effects of landscape fragmentation on the dioecious population sex ratio were mainly achieved in relation to changing soil nitrogen conditions in patches and pollen limitation within and among populations. Large populations could maintain a more suitable environment in terms of nutrient conditions and pollen flow, subsequently maintaining a stable sex ratio in dioecious plant populations. Both micro-environmental factors and spatial structure should be considered in fragmented landscape for the conservation of dioecious plant species.
中国浙江省千岛湖地区是一个高度破碎的景观，由于洪水形成水库，景观在某一特定时刻发生了明显的破碎化。对人工湖中岛屿进行了调查，以研究雌雄异株植物黄连木的种群性别比例如何受到景观破碎化的影响。还对湖泊附近大陆上的一个自然种群进行了调查，作为比较。在两年的时间里，对种群规模、个体性别比例和胸径（DBH）进行了测量。研究了分布在 31 个种群中的 1500 多个个体。测量了不同种群的土壤氮含量，以确定性别比例与微环境条件之间的关系。与许多其他关于环境梯度与偏性性别比例关系的报告结果一致，我们发现贫瘠的土壤氮区有利于雄性偏性种群。此外，随着种群规模和连通性的降低，性别比例偏性程度增加。偏性性别比例仅在小种群中较年轻的个体（小于 50 岁）中发现，而大陆上大种群中则发现了稳定的 1∶1 性别比例。我们得出结论，景观破碎化对雌雄异株种群性别比例的影响主要是通过斑块中土壤氮条件的变化以及种群内和种群间的花粉限制来实现的。大种群在养分条件和花粉流方面可以维持更适宜的环境，从而维持雌雄异株植物种群的稳定性别比例。在破碎景观的保护中，应该考虑微环境因素和空间结构。
