Jetz W, Rahbek C
Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, United Kingdom.
Proc Natl Acad Sci U S A. 2001 May 8;98(10):5661-6. doi: 10.1073/pnas.091100998.
The world contains boundaries (e.g., continental edge for terrestrial taxa) that impose geometric constraints on the distribution of species ranges. Thus, contrary to traditional thinking, the expected species richness pattern in absence of ecological or physiographical factors is unlikely to be uniform. Species richness has been shown to peak in the middle of a bounded one-dimensional domain, even in the absence of ecological or physiographical factors. Because species ranges are not linear, an extension of the approach to two dimensions is necessary. Here we present a two-dimensional null model accounting for effects of geometric constraints. We use the model to examine the effects of continental edge on the distribution of terrestrial animals in Africa and compare the predictions with the observed pattern of species richness in birds endemic to the continent. Latitudinal, longitudinal, and two-dimensional patterns of species richness are predicted well from the modeled null effects alone. As expected, null effects are of high significance for wide ranging species only. Our results highlight the conceptual significance of an until recently neglected constraint from continental shape alone and support a more cautious analysis of species richness patterns at this scale.
世界存在着边界（例如，陆地生物分类群的大陆边缘），这些边界对物种分布范围施加了几何约束。因此，与传统观念相反，在没有生态或自然地理因素的情况下，预期的物种丰富度模式不太可能是均匀的。即使在没有生态或自然地理因素的情况下，物种丰富度已被证明在有界一维区域的中间达到峰值。由于物种分布范围不是线性的，因此有必要将该方法扩展到二维。在这里，我们提出了一个考虑几何约束影响的二维零模型。我们使用该模型来研究大陆边缘对非洲陆地动物分布的影响，并将预测结果与该大陆特有鸟类的物种丰富度观测模式进行比较。仅从模拟的零效应就可以很好地预测物种丰富度的纬度、经度和二维模式。正如预期的那样，零效应仅对分布广泛的物种具有高度显著性。我们的结果突出了直到最近才被忽视的仅来自大陆形状的约束的概念意义，并支持在这个尺度上对物种丰富度模式进行更谨慎的分析。
