Autofertility and self-compatibility moderately benefit island colonization of plants

Aim: The current geographical distribution of species largely reflects colonization success after natural long‐distance dispersal or introduction by humans. Plants with selfing ability should have an advantage when establishing on islands where mates and pollinators are limited (Baker's law). However, high percentages of dioecious and self‐incompatible species have been reported for some islands, possibly resulting from post‐colonization evolution. Given that such evolution is less likely to apply to alien species recently introduced to islands by humans, tests of Baker's law on islands need to consider both native and naturalized alien species. Location: Global. Time period: Undefined. Major taxa studied: Angiosperms. Methods: To test whether the colonization of islands is associated with selfing ability (self‐compatibility and autofertility), we combined three comprehensive global databases: one on breeding systems of species, one on island and mainland distributions of native species and one on global naturalization of alien plants. We assigned each of a total of 1,752 species, from 161 angiosperm families, as mainland species, island colonists and/or island endemics (i.e., species that are restricted to islands). To assess potential relationships between island occurrence and selfing ability of species, we used multinomial logistic regressions.
Results: We found that species with high selfing ability were slightly more likely to be island colonist than mainland species. However, selfing ability did not increase the likelihood of being an island endemic in contrast to mainland species. Among island colonists, selfing ability did not differ between species on oceanic and on continental islands or between species native to islands and naturalized on islands. Main conclusions: We performed a comprehensive test of Baker's law by considering many angiosperm families, using continuous metrics of self‐compatibility and autofertility and including both native and naturalized species. We provide global evidence that high selfing ability may foster island colonization of angiosperms.

研究目的：当前物种的地理分布格局在很大程度上反映了其自然长距离扩散后，或经人类引种后的定殖成功情况。在配偶与传粉者均匮乏的岛屿上，具备自交能力的植物在定殖时应具备竞争优势（贝克法则（Baker's law））。但已有研究报道，部分岛屿上雌雄异株（dioecious）与自交不亲和（self-incompatible）物种的占比颇高，这或许源于定殖后的演化过程。鉴于经人类近期引种至岛屿的外来物种不太可能经历此类定殖后演化，针对岛屿的贝克法则检验需同时纳入本土物种与归化外来物种（naturalized alien species）。
研究区域：全球范围。
研究时间跨度：未明确。
研究类群：被子植物（Angiosperms）。
研究方法：为检验岛屿定殖是否与自交能力（selfing ability）相关，本研究整合了三个全球综合数据库：其一涵盖物种繁育系统信息，其二包含本土物种的岛屿与大陆分布数据，其三收录全球外来植物归化情况。本研究共纳入161个被子植物科的1752个物种，将其分别归类为大陆物种、岛屿定殖物种及/或岛屿特有物种（即仅分布于岛屿的物种）。为评估物种的岛屿分布情况与自交能力间的潜在关联，本研究采用多项逻辑回归（multinomial logistic regressions）分析。
研究结果：本研究发现，自交能力较强的物种相较于大陆物种，成为岛屿定殖物种的概率略高。但与大陆物种相比，自交能力并未提升物种成为岛屿特有种的可能性。在岛屿定殖物种中，海洋岛与大陆岛物种的自交能力并无差异，岛屿本土物种与归化物种的自交能力亦无显著不同。
主要结论：本研究通过纳入多个被子植物科、采用自交亲和性（self-compatibility）与自动结实性（autofertility）的连续量化指标，并同时涵盖本土与归化物种，对贝克法则开展了全面检验。本研究提供了全球尺度的证据，表明较高的自交能力可促进被子植物的岛屿定殖。