海南特有毛花马铃苣苔小尺度局域种群的年龄结构与基因流

摘要

从局部地形揭示植物种群的空间分布、年龄组成与个体迁移,可深入揭示种群动态与适应潜力,为制定有效的保育措施提供依据.笔者选取海南岛高山特有附生石上、局域种群界限清晰的毛花马铃苣苔(Oreocharis dasyantha)4个地理种群,首先研究每个地理种群内主要斑块(小尺度局域种群)的个体年龄结构和静态生命表,然后利用核基因片段ITS和2个叶绿体基因片段(trn L-F,ycf1b)分析各斑块种群的遗传结构与斑块间的基因流强度.结果表明,位于海南岛湿润区的毛花马铃苣苔种群呈增长型,而位于海南岛干旱区的种群则呈下降型.同一地点的小尺度局域种群之间的年龄结构、增长率、死亡率和消失率等也都存在较大差异,并出现了私有单倍型.这可能是由于坡谷、栈道等微地形的隔离效应,导致扩散能力较弱的毛花马铃苣苔在小尺度(10 m左右)上出现了基因流的阻断.因此,对于繁殖体扩散能力较差的草本植物而言,即使在较小尺度上也要维持繁殖体迁移畅通的廊道,避免坡谷、栈道等微地形对基因流的不良效应,保证野外种群长期的就地保育.%The spatial distribution,age structure and individual migration of plant populations in a partial landform might give a deep revelation of dynamics and potential adaptivity of plant populations,which is a good reference for formulation of effective conservation measures for the plant populations.Four geographic populations of Oreocharis dasyantha,an epiphytic herb endemic to mountains in Hainan Island,which grow on rocks and are distinctly different in population at four sites,were selected to study their age structure and life table for each patch (fine-scale local population) within each geographic population,and to analyze the genetic structure and the intensity of gene flow between the patch populations by using the nuclear gene ITS and two chloroplast genes (trn L-F,ycf1b).The results show that the O.dasyantha populations tended to expand in the humid area of Hainan Island but tended to decline in the dry area of Hainan Island.The fine-scale local populations of O.dasyantha within the same site differed greatly in age structure,growth rate,mortality and disappearance rate,and were found to have private haplotypes growing in the same site.This may be due to the isolation effect of microtopography,such as the slope valley and the path,which led to the blocking of gene flow of O.dasyantha with weak dispersal ability on the fine scale (about 10 m).Therefore,for herbaceous plants with poor dispersal ability,it is necessary to maintain a smooth corridor for reproduction even at the fine-scale level,so as to avoid adverse effects of microhabitat such as slope valley and road to ensure long-term field conservation of the wild populations.