Data from: Island properties dominate species traits in determining plant colonizations in an archipelago system

The extrinsic determinants hypothesis emphasizes the essential role of environmental heterogeneity in species' colonization. Consequently, high resident species diversity can increase community susceptibility to colonizations because good habitats may support more species that are functionally similar to colonizers. On the other hand, colonization success is also likely to depend on species traits. We tested the relative importance of environmental characteristics and species traits in determining colonization success using census data of 587 vascular plant species collected about 80 years apart from 471 islands in the archipelago of SW Finland. More specifically, we explored potential new colonization as a function of island properties (e.g., location, area, habitat diversity, number of resident species per unit area), species traits (e.g., plant height, life-form, dispersal vector, Ellenberg indicator values, association with human impact), and species' historical distributions (number of inhabited islands, nearest occurrence). Island properties and species' historical distributions were more effective than plant traits in explaining colonization outcomes. Contrary to the extrinsic determinants hypothesis, colonization success was neither associated with resident species diversity nor habitat diversity per se, although colonization was lowest on sparsely vegetated islands. Our findings lead us to propose that while plant traits related to dispersal and establishment may enhance colonization, predictions of plant colonizations primarily require understanding of habitat properties and species' historical distributions.

外在决定因子假说（extrinsic determinants hypothesis）强调了环境异质性在物种定殖过程中的核心作用。据此，高本地物种多样性可提升群落对定殖的易感性，因为优质栖息地能够支撑更多与定殖者功能相似的物种。另一方面，定殖成功也可能取决于物种性状。本研究借助芬兰西南部群岛471个岛屿上、间隔约80年采集的587种维管植物（vascular plant）普查数据，检验了环境特征与物种性状在决定定殖成功方面的相对重要性。具体而言，我们将潜在新定殖事件作为岛屿属性（如位置、面积、栖息地多样性、单位面积本地物种数）、物种性状（如植株高度、生活型、扩散媒介、埃伦贝格指示值（Ellenberg indicator values）、与人类活动的关联）以及物种历史分布（即占据岛屿数量、最近分布点）的函数进行分析。结果显示，岛屿属性与物种历史分布对定殖结果的解释力强于植物性状。与外在决定因子假说相悖的是，定殖成功本身既未与本地物种多样性相关，也未与栖息地多样性相关，尽管植被稀疏的岛屿上定殖率最低。我们的研究结果表明，尽管与扩散和定植相关的植物性状可能提升定殖成功率，但预测植物定殖事件首要需要充分了解栖息地属性与物种的历史分布情况。