Data from: Island Biogeography, the effects of taxonomic effort and the importance of island niche diversity to single island endemic species

Island biogeography theory is fundamentally reliant on measuring the number of species per island and hence has taxonomy at its foundation. Yet as a metric used in tests of the theory, island species richness (S) has varied with time according to the level of taxonomic effort (a function of the rate of finding and describing species). Studies using a derivative of S, single-island endemic species richness (SIE S), may be prone to change in taxonomic effort. Decreases or increases in species numbers resulting from taxonomic revision or increased sampling are likely to have a large effect on values of SIE S, as they tend to be smaller than total S for the same island. Using simple biogeography models, we analysed estimates of SIE S in plants, land snails, beetles, and fungi from comprehensive data sets for eight island groups, produced species accumulation curves and applied Bayesian regression over five time periods. Explanatory power differed across taxa, but area and island age were not always the best explanatory variables, and niche diversity appeared to be important. Changing levels of SIE S over time had different effects on models with different taxa and between island archipelagos. The results indicated that the taxonomic effort that determines SIE S is important. However, as this cannot often be quantified, we suggest Bayesian approaches should be more useful than frequentist methods in evaluating SIE S in island biogeography theory. Fundamentally, the article highlights the importance of taxonomy to theoretical biogeography.

岛屿生物地理学理论（island biogeography theory）本质上依赖于对每座岛屿的物种数量进行测算，因此分类学是其核心基础。然而，作为检验该理论所使用的指标，岛屿物种丰富度（island species richness，简称S）会随分类学研究投入（taxonomic effort）水平的变化而随时间波动——该投入水平是物种发现与描述速率的函数。以S的衍生指标——单岛特有物种丰富度（single-island endemic species richness，简称SIE S）——为研究对象的分析，可能会因分类学研究投入的变化而出现结果波动。因分类学修订或采样量增加导致的物种数量增减，很可能会对SIE S的数值产生显著影响，因为相较于同一岛屿的总物种丰富度S，单岛特有物种的数量往往更少。本研究借助简化的生物地理学模型，对涵盖8个岛屿群的综合数据集内的植物、陆生螺类、甲虫以及真菌的单岛特有物种丰富度估算值展开分析，构建了物种累积曲线，并针对五个时间阶段开展贝叶斯回归（Bayesian regression）分析。不同生物类群的模型解释力存在差异，但岛屿面积与岛屿年龄并非始终为最优解释变量，而生态位多样性似乎发挥着重要作用。随时间变化的SIE S水平，对不同生物类群的模型以及不同群岛的模型产生的影响各不相同。研究结果表明，决定SIE S数值的分类学研究投入十分关键。然而，这类投入往往难以量化，因此我们建议，在岛屿生物地理学理论框架下评估SIE S时，贝叶斯方法相较于频率学派方法（frequentist methods）更为适用。从根本上来说，本文凸显了分类学对理论生物地理学的重要意义。