Islands, mainland, and terrestrial fragments: How isolation shapes plant diversity
Islands, mainland, and terrestrial fragments: How isolation shapes plant diversity
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岛屿、大陆和陆地碎片：隔离如何塑造植物多样性
作者：
E. Martín;C. Albert;Pierre;A. Saatkamp
摘要自然栖息地的碎片化是对生物多样性的主要威胁。然而，与人为破碎相比，导致物种丧失的自然隔离机制的影响和空间规模尚不清楚，主要是由于碎片和岛屿之间的差异，如基质渗透性。我们研究了法国500平方公里的地中海地区，包括城市栖息地碎片、连续栖息地和大陆架岛屿。在2 95个S植物区系释放的基础上，我们建立了物种-面积关系，以比较城市化后片断中的隔离，以及连续生境和大陆架岛屿。我们通过图论假设栖息地的可达性为无扩散、无限扩散或估计中等水平。隔离机制以碎片形式出现，但强度低于近岸岛屿，最重要的是影响多年生植物。一年生植物受到的影响较小，可能是因为它们的体型较小，生命周期较短。分离发生在景观水平的碎片和岛屿的斑块水平上。可达栖息地的数量(占空间配置)解释了两个系统中当地物种的丰富度，但栖息地的数量(不考虑空间配置)已经是一个很好的预测因子。这些结果表明，碎片周围的栖息地数量在减轻近岸岛屿观察到的隔离效应方面发挥了重要作用，以及仔细考虑不同功能组的重要性。
Abstract The fragmentation of natural habitats is a major threat for biodiversity. However, the impact and spatial scale of natural isolation mechanisms leading to species loss, compared to anthropogenic fragmentation, are not clear, mainly due to differences between fragments and islands, such as matrix permeability. We studied a 500 km2 Mediterranean region in France, including urban habitat fragments, continuous habitat, and continental‐shelf islands. On the basis of 295 floristic relevés, we built species–area relationships to compare isolation in fragments after urbanization, with continuous habitat and continental‐shelf islands. We assumed either no dispersal, infinite dispersal, or estimated intermediate levels of habitat reachability through graph theory. Isolation mechanisms occurred in fragments but with a lower strength than in near‐shore islands, and most importantly affected perennial plants. Annual plants were less affected, probably due to their smaller size and shorter life cycle. Isolation occurred at landscape level in fragments and at patch level in islands. The amount of reachable habitat (accounting for spatial configuration) explained local species richness in both systems, but the amount of habitat (no consideration of spatial configuration) was already a good predictor. These results suggest an important role of habitat amount around fragments in mitigating the isolation effects observed in near‐shore islands, and the importance of carefully considering different functional groups.