高山垫状植物团状福禄草开花面积与方位随海拔的变化及其适应性

Altitudinal variation in flowering area and position and their ecological significances of an alpine cushion Arenaria polytrichoides,a gynodioecious herb

作为高山生态系统中的奠基种(foundation species),垫状植物自身种群的繁殖与扩张,对高山生态系统功能稳定性起着关键作用。但是,垫状植物如何在极端环境条件下实现资源的有效利用与分配,达到繁殖最优化,至今鲜为人知。该研究在滇西北白马雪山沿海拔梯度选择具有不同坡度及坡向的5个团状福禄草(Arenaria polytrichoides)种群,调查、比较种群内、种群间以及具有不同性系统的植株个体之间的开花面积比、开花方位,并分析不同生态因子对其开花特性的影响。结果表明:随着海拔的升高,团状福禄草个体变小,其分配到开花的资源比例总体上随海拔上升呈现下降的趋势,说明团状福禄草的繁殖分配受到由海拔所引起的生态因子的调控。但是,部分低海拔种群内植物个体的繁殖分配显著低于部分高海拔种群,说明海拔并非控制植物繁殖分配的唯一因素。此外,植株开花总面积随植株个体增大而增加,但开花面积比却随个体增大而变小,说明植株分配到开花的资源增长速率可能低于植株个体的增长速率。在性别差异方面,两性植株对开花的资源分配比例要显著高于雌性植株,但是,其差异程度受到海拔因素的影响。最后,在同一种群内,团状福禄草在冠层表面不同方位上的开花面积比存在显著差异性,这种差异性在不同种群之间又具有不同的表现形式。

Aims As foundation species in the alpine ecosystems,the reproduction and recruitment of alpine cushion plants are very important for sustaining the alpine ecosystem functions.However,it still remains unclear that how cushion plants effectively allocate resources to optimize reproductive fitness.Methods Here we selected five populations of a gynodioecious herb Arenaria polytrichoides with different exposures and slopes along an altitudinal gradient on the Baima snow mountain in northwest Yunnan,southwest China,to investigate and compare flowering area and positions,within and among populations and between female and hermaphroditic morphs.By doing so,we further discuss how the environmental stresses affect the cushion’s flowering attributes thus the population-level reproduction.Important findings The results showed that,individual plant size and resources allocated to flowering(flowering area%)both decreased with increasing elevation,indicating that the reproductive allocation strategy was significantly affected by elevation.However,a population at lower elevation showed lower reproductive investment than higher populations,suggesting that elevation was not the only factor affecting the cushion’s reproductive allocation.In addition,absolute flowering area increased with increasing individual size,but the flowering area ratio decreased,indicating that the increases in reproductive allocation are fewer than that in vegetative allocation.Hermaphroditic individuals invested more resources to flowering than females did,but again,such effect was affected by elevation.Moreover,within a single population,the flowering areas were significantly different among the four directions(east,south,west and north)within one single individual canopy,but such differences varied in different populations.