Invasion in a diversity hotspot: exotic cover and native richness in the Californian serpentine flora.
Invasion in a diversity hotspot: exotic cover and native richness in the Californian serpentine flora.
复制标题
多样性热点地区的入侵：加利福尼亚蛇纹石植物区系的异国情调和本土丰富性。
作者：
S. Harrison;J. Grace;K. Davies;H. Safford;J. Viers
外来物种已被观察到更普遍的本地物种的丰富度是最高的网站，可能反映了资源，繁殖体供应，异质性，或干扰的网站之间的变化。然而，这种模式并不清楚物种丰富的地方的本地人是否因此受到外来物种的特别严重的影响。我们认为这个问题使用路径模型，在相关的环境因素的存在下，外来覆盖和本地丰富度之间的关系进行了评估。在整个加州，美国的蛇纹石土壤上的109个站点，异国情调的覆盖与总本土草本植物的丰富程度呈正相关，并与蛇纹石特有的和稀有的本土草本植物的丰富程度呈负相关。然而，在路径模型，占土壤化学的影响，干扰，overstory覆盖，区域降雨量和海拔高度，我们没有发现任何迹象表明，外来覆盖减少任何组成部分的原生草本植物丰富度。相反，我们的研究结果表明，有利于外来的，本地的，特有的和稀有物种的条件的相似性和差异。我们的研究结果表明，尽管有一些本地化的影响，外来物种并没有发挥可检测的整体影响的社区丰富度独特的本土植物群的加利福尼亚蛇纹石。
Exotic species have been observed to be more prevalent in sites where the richness of native species is highest, possibly reflecting variation among sites in resources, propagule supply, heterogeneity, or disturbance. However, such a pattern leaves unclear whether natives at species-rich sites are subject to especially severe impacts from exotics as a result. We considered this question using path models in which relationships between exotic cover and native richness were evaluated in the presence of correlated environmental factors. At 109 sites on serpentine soils across California, USA, exotic cover was positively correlated with total native herbaceous richness and was negatively correlated with the richness of both serpentine-endemic and rare native herbs. However, in path models that accounted for the influences of soil chemistry, disturbance, overstory cover, and regional rainfall and elevation, we found no indication that exotic cover reduced any component of native herb richness. Rather, our results indicated similarities and differences in the conditions favoring exotic, native, endemic, and rare species. Our results suggest that, in spite of some localized impacts, exotic species are not exerting a detectable overall effect on the community richness of the unique native flora of Californian serpentine.