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.

理论表明，确定性因子（deterministic factor）与随机性因子（stochastic factor）以各异路径参与群落构建（community assembly）过程：环境过滤（environmental filter）作用会调控在特定区域成功定植的物种，使得物种的生态位需求成为物种分布格局的核心驱动因子；而偶然事件与扩散限制（dispersal limitation）则决定物种抵达特定区域的概率，此时物种生态特征基本呈现中性。上述因子对于解析不同生境（habitat）或岛屿（island）的面积与隔离度如何交互影响群落组成（community composition）具有关键意义。我们对现有文献的综述显示，极少有实验研究（experimental study）探讨生境面积与隔离度对群落构建的交互效应，且相关实验结果莫衷一是。我们通过调控草原基质（grassland matrix）中全新构建的岩石‘岛屿’的面积与隔离度，实验验证确定性与随机性因子如何塑造拓殖动物群落（colonizing animal community）。为期64周的实验结果表明，确定性因子在群落构建中占据主导地位：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。尽管如此，不同分类群（taxon）的多度不均等性仍存在显著差异：相较于其余所有岛屿类型，面积较大且隔离度较低的岛屿中常见分类群的数量始终更高。在小空间尺度下，扩散限制常被认为可忽略不计，但我们的研究数据表明事实并非如此。此外，部分物种的扩散限制可能产生复杂的级联效应（flow-on effect），进而影响调控其他拓殖物种的确定性因子类型。