美国《国家科学院院刊》（PNAS）日前刊登了题为《区域异质性的代价以及生态群落多样性》的研究论文，提出了一个与以往不同的生物多样性假说。
　　1平方米的草地上如何能包含几十种植物物种？什么因素决定了一个生态系统中的物种数量？这两个问题无论对于理解自然还是对于自然生态系统对人类的价值，都具有很重要的意义。自然生态系统所提供的服务和产品超过地球上全部的GDP。近50年来，传统的生态学理论认为，在特定的区域可以共存的物种数量随着栖息地环境条件异质性的升高而增加。来自耶路撒冷的学者Omri Allouche和Michael Kalyuzhny在一项研究中对这项传统假设进行了重新检验。研究指出，在异质性的环境（其中存在着多种不同类型栖息地）中，每个物种拥有更少的资源和更不适宜的环境，使这些物种更加容易走向灭绝。这导致另一种假设：过度的栖息地异质性可能减少物种的数量。
　　研究人员利用数学分析和生态系统实证分析方法对此项假设进行了检验。该假设的预测检验是采用元分析的方法，数据来源于世界各地的数十个动植物物种的数据库。通过分析发现，理论和数据分析都支持新的假设，即栖息地异质性可能提高物种灭绝的速度。

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PNAS发表论文摘要（英文）

Area–heterogeneity tradeoff and the diversity of ecological communities

For more than 50 y ecologists have believed that spatial heterogeneity in habitat conditions promotes species richness by increasing opportunities for niche partitioning. However, a recent stochastic model combining the main elements of niche theory and island biogeography theory suggests that environmental heterogeneity has a general unimodal rather than a positive effect on species richness. This result was explained by an inherent tradeoff between environmental heterogeneity and the amount of suitable area available for individual species: for a given area, as heterogeneity increases, the amount of effective area available for individual species decreases, thereby reducing population sizes and increasing the likelihood of stochastic extinctions. Here we provide a comprehensive evaluation of this hypothesis. First we analyze an extensive database of breeding bird distribution in Catalonia and show that patterns of species richness, species abundance, and extinction rates are consistent with the predictions of the area–heterogeneity tradeoff and its proposed mechanisms. We then perform a metaanalysis of heterogeneity–diversity relationships in 54 published datasets and show that empirical data better fit the unimodal pattern predicted by the area–heterogeneity tradeoff than the positive pattern predicted by classic niche theory. Simulations in which species may have variable niche widths along a continuous environmental gradient are consistent with all empirical findings. The area–heterogeneity tradeoff brings a unique perspective to current theories of species diversity and has important implications for biodiversity conservation.