中域效应假说:模型、证据和局限性

The mid-domain effect hypothesis: models, evidence and limitations

物种多样性的地理格局是宏观生态学和生物地理学的核心问题之一,中域效应假说是该领域的一项重要的理论进展。中域效应是指由于边界对物种分布构成限制,使不同物种分布区在区域中间重叠程度较大,而在边界附近重叠较少,从而形成物种丰富度从边界向中心逐渐增加的格局。现有研究表明,中域效应是影响物种丰富度格局的一种重要机制,但其作用大小受很多因素的影响。本文介绍该假说的基本假设和模型,模拟分析不同模型之间的差异,并就中域效应假说所展开的争论进行综述,指出该假说的合理性和局限性。我们认为,中域效应假说的重要性在于揭示了几何(边界)限制和随机过程在物种多样性地理格局中的作用,但其目前的模型和假设还过于简单,需要在深入理解物种分布机制的基础上进行完善和发展。

Geographic patterns of species diversity and their underlying mechanisms have long been the focus of macro-ecology and biogeography. Recently, the mid-domain effect （MDE） hypothesis has been proposed to explain geographical diversity patterns. The hypothesis states that if the ranges of the species are randomly distributed within a bounded domain then more ranges will overlap near the middle of the domain than at the edges, and thus decreasing species richness will be observed from the mid-domain to the edges. Many studies have shown that the MDE is an important mechanism affecting geographic richness pattern. However, its relative role in such patterns differs markedly depending on many factors. In this paper, we introduced the assumptions and basic models of the hypothesis and illustrate that the models differ in their predictions as a result of different assumptions. We also review the debate on the MDE hypothesis, and discuss the limitations of present mid-domain models. Although the hypothesis has improved our understanding of the effects of geometric constraints and random process on geographic richness gradients, current MDE models are too simplistic to describe biodiversity patterns in the real world. Improvements to mid-domain models should be based on a better understanding of the mechanisms underlying species distribution.