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）本质上依赖于对单个岛屿的物种数量进行测算，因此分类学（taxonomy）是其核心基础。然而，作为检验该理论所用的一项指标，岛屿物种丰富度（S）会随时间推移发生变化，其变化幅度取决于分类学投入水平——即发现与描述物种速率的函数。以S的衍生指标单岛特有物种丰富度（SIE S）开展的研究，可能会因分类学投入的变动而受到影响。因分类学修订或采样量增加而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，因为单岛特有物种丰富度通常低于同一岛屿的总物种丰富度S。本研究借助简单的生物地理学模型，对8个群岛的综合数据集内植物、陆生螺类、甲虫与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。不同类群的解释能力存在差异，但岛屿面积与岛屿年龄并非始终是最优的解释变量，而生态位多样性似乎具有重要影响。随时间推移的SIE S水平变化，对不同类群的模型以及不同群岛的模型所产生的影响各不相同。研究结果表明，决定SIE S数值的分类学投入至关重要。但由于这类投入通常难以量化，我们建议在岛屿生物地理学理论框架下评估SIE S时，贝叶斯方法要优于频率学派方法（frequentist methods）。从根本上来说，本文强调了分类学对理论生物地理学的重要意义。