Data from: Manipulation of habitat isolation and area implicates deterministic factors and limited neutrality in community assembly

Theory predicts deterministic and stochastic factors will contribute to community assembly in different ways: environmental filters should regulate those species that establish in a particular area resulting in the ecological requirements of species being the primary driver of species distributions, while chance and dispersal limitation should dictate the likelihood of species reaching certain areas with the ecology of species being largely neutral. These factors are specifically relevant for understanding how the area and isolation of different habitats or islands interact to affect community composition. Our review of the literature found few experimental studies have examined the interactive effect of habitat area and isolation on community assembly, and the results of those experiments have been mixed. We manipulated the area and isolation of rock ‘islands’ created de novo in a grassland matrix to experimentally test how deterministic and stochastic factors shape colonizing animal communities. Over 64 weeks, the experiment revealed the primacy of deterministic factors in community assembly, with habitat islands of the same size exhibiting remarkable consistency in community composition and diversity, irrespective of isolation. Nevertheless, tangible differences still existed in abundance inequality among taxa: large, near islands had consistently higher numbers of common taxa compared to all other island types. Dispersal limitation is often assumed to be negligible at small spatial scales, but our data shows this not to be the case. Furthermore, the dispersal limitation of a subset of species has potentially complex flow-on effects for dictating the type of deterministic factors affecting other colonising species.理论预测，确定性因素（deterministic factors）与随机性因素（stochastic factors）会通过不同途径影响群落组装（community assembly）：环境过滤作用（environmental filters）会筛选能够在特定区域定殖的物种，使得物种的生态需求成为物种分布的主要驱动因子；而偶然性与扩散限制（dispersal limitation）则决定物种抵达特定区域的概率，此时物种的生态位特征基本呈中性。这些因素对于解析不同生境或岛屿的面积与隔离度如何共同影响群落组成（community composition）具有关键意义。我们对现有文献的综述发现，鲜有实验研究探讨生境面积与隔离度对群落组装的交互效应，且现有相关实验的结果并不一致。本研究通过操控草原基质（grassland matrix）中从头创建（de novo）的岩石‘岛屿’的面积与隔离度，开展实验以检验确定性与随机性因素如何塑造定殖动物群落（colonizing animal communities）。在为期64周的实验周期内，结果显示确定性因素在群落组装中占据主导地位：相同面积的生境岛屿，无论隔离度如何，其群落组成与多样性均表现出极高的一致性。但分类群（taxa）间的丰度不平等仍存在显著差异：与其他所有岛屿类型相比，面积较大且隔离度较低的岛屿中常见类群的数量始终更高。此前通常认为，小空间尺度下的扩散限制可以忽略不计，但本研究的数据表明事实并非如此。此外，部分物种的扩散限制可能会产生复杂的级联效应（flow-on effects），进而影响调控其他定殖物种的确定性因素类型。