Plant diversity in oceanic archipelagos: realistic patterns emulated by an agent‐based computer simulation

Although islands as natural laboratories have held the attention of scientists for centuries, they continue to offer new study questions, especially in the context of the current biodiversity crisis. To date, habitat diversity on islands and spatial configuration of archipelagos have received less attention than classical island area and isolation. Moreover, in the field where experiments are impossible, correlative methods have dominated, despite the call for more mechanistic approaches. We developed an agent‐based computer simulation to study the effect of habitat diversity and archipelago configuration on plant species richness and composition in five archipelagos worldwide (Hawaii, Galapagos, Canary Islands, Cape Verde and Azores) and compared simulated diversity patterns to the empirical data. Habitat diversity proved to be an important factor to achieve realistic simulation results in all five archipelagos, whereas spatial structure of archipelagos was important in more elongated archipelagos. In most cases, simulation results correlate stronger with spermatophyte than with pteridophyte data, which we suggest can be attributed to the different dispersal and evolution rates of the two species groups. Correlation strength between simulated and observed diversity also varied among archipelagos, suggesting that geological and biogeographic histories of archipelagos have affected the species richness and composition on the islands. Our study demonstrates that a relatively simple computer simulation involving just a few essential processes can largely emulate patterns of archipelagic species richness and composition and serve as a powerful additional method to complement empirical approaches.

尽管岛屿作为天然实验室（natural laboratories）早已吸引科学家们的持续关注达数百年之久，时至今日，它们仍能催生全新的研究课题，尤其在当前生物多样性危机的背景下。迄今为止，相较于经典的岛屿面积与岛屿隔离度指标，岛屿生境多样性及群岛（archipelagos）空间构型的研究关注度仍相对不足。此外，在无法开展受控实验的研究领域中，尽管学界始终呼吁采用更多机制性研究方法，现有研究仍多以相关分析法为主。本研究开发了基于智能体的计算机模拟（agent-based computer simulation）模型，用以探究全球5处群岛——夏威夷群岛、加拉帕戈斯群岛、加那利群岛、佛得角群岛及亚速尔群岛——的生境多样性与群岛构型对植物物种丰富度与物种组成的影响，并将模拟所得的多样性格局与实测野外数据进行对比。研究表明，生境多样性是实现5处群岛逼真模拟结果的核心影响因素，而群岛空间结构则在形态更为狭长的群岛中发挥关键作用。多数情况下，模拟结果与种子植物（spermatophyte）实测数据的相关性显著强于蕨类植物（pteridophyte），我们推测这一现象可归因于两类物种群截然不同的扩散策略与演化速率。模拟结果与观测多样性间的相关强度也因群岛而异，这表明群岛的地质与生物地理历史会显著影响岛屿上的物种丰富度与物种组成。本研究证实，仅包含少数核心过程的相对简易的计算机模拟，即可在较大程度上复刻群岛的物种丰富度与物种组成格局，可作为补充实证研究方法的有力工具。