http://onlinelibrary.wiley.com/doi/10.1111/j.1600-0587.2012.07669.x/abstract

Weigelt, P. and Kreft, H. (2013), Quantifying island isolation – insights from global patterns of insular plant species richness. Ecography, 36: 417–429. doi: 10.1111/j.1600-0587.2012.07669.x

Isolation is a driving factor of species richness and other island community attributes. Most empirical studies have investigated the effect of isolation measured as distance to the nearest continent. Here we expanded this perspective by comparing the explanatory power of seventeen isolation metrics in sixty-eight variations for vascular plant species richness on 453 islands worldwide. Our objectives were to identify ecologically meaningful metrics and to quantify their relative importance for species richness in a globally representative data set. We considered the distances to the nearest mainland and to other islands, stepping stone distances, the area of surrounding landmasses, prevailing wind and ocean currents and climatic similarity between source and target areas. These factors are closely linked to colonization and maintenance of plant species richness on islands. We tested the metrics in spatial multi-predictor models accounting for area, climate, topography and island geology. Besides area, isolation was the second most important factor determining species richness on the studied islands. A model including the proportion of surrounding land area as the isolation metric had the highest predictive power, explaining 86.1% of the variation. Distances to large islands, stepping stone distances and distances to climatically similar landmasses performed slightly better than distance to the nearest mainland. The effect of isolation was weaker for large islands suggesting that speciation counteracts the negative effect of isolation on immigration on large islands. Continental islands were less affected by isolation than oceanic islands. Our results suggest that a variety of immigration mechanisms influence plant species richness on islands and we show that this can be detected at macro-scales. Although the distance to the nearest mainland is an adequate and easy-to-calculate measure of isolation, accounting for stepping stones, large islands as source landmasses, climatic similarity and the area of surrounding landmasses increases the explanatory power of isolation for species richness.

隔离是岛屿物种丰富度和其它群落特征形成的主要因素。大多数的实证研究都分析了用与最近大陆的距离为隔离指标的隔离效应。本文中我们通过比较用68种测量方法测定的17个隔离指标对世界范围内453个岛屿的维管植物种类丰富度的解释度拓展了对隔离效应的理解。我们的目标是用全球范围内有代表性的数据确定对解释岛屿物种丰富度有生态意义的测量指标并定量确定其相对重要性。我们考虑了岛屿到最近大陆和其它岛屿的距离、跳板距离、周围大陆面积、主要风向和洋流以及物种源和研究地的气候相似性。这些因素都和物种在岛屿上定居和长期存活紧密相关。我们用包含了岛屿面积、气候、地形和地质的空间多预测因素模型来检验了各个隔离指标。除了面积，岛屿的隔离度是决定所研究岛屿上物种丰富度第二重要的因素。一个包含了岛屿周围陆地面积所占比例的隔离指标有最高的预测能力，能解释86.1%的变异。与大岛的距离、跳板距离和与气候相似的大陆的距离的预测能力比与最近大陆的距离稍微稍好。隔离对大岛的效应较弱暗示大岛上新物种抵消了隔离对物种迁移到岛上的负面影响。大陆型岛屿受到隔离的影响比火山型岛屿要小。本研究的结果岛屿的物种丰富度受到多种迁移机制的影响，并且我们证明了这些影响可以在大尺度上检测出来。尽管与最近大陆的距离是一个够好并且容易计算的隔离指标，但是如果能考虑跳板、大岛作为物种源、气候相似性和围绕岛屿陆地的面积就能增加隔离对物种丰富度的解释能力。