Stevens Richard D
Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
Proc Biol Sci. 2006 Sep 22;273(1599):2283-9. doi: 10.1098/rspb.2006.3596.
One of the more vexing issues in ecology is how historical processes affect contemporary patterns of biodiversity. Accordingly, few models have been presented. Two corollary models (centre of origin, time-for-speciation) can be used to make quantitative predictions characterizing the tropical niche conservatism hypothesis and describe diversification as diffusion and subsequent cladogenesis of species away from the place of origin of a higher taxon in the tropics. Predictions derived from such models are: (i) species richness declines toward the periphery of the range of a higher taxon; (ii) taxa are more derived toward the periphery than the centre; (iii) ages of taxa are lower toward the periphery than the centre; and (iv) ages and measures of derivedness are less variable toward the periphery of the range of a higher taxon. I tested these predictions to better understand the formation of one of the most ubiquitous patterns of biodiversity-the latitudinal gradient in species richness. Results indicate well-supported predictions for New World leaf-nosed bats and that diversification has had strong influences on latitudinal gradients of species richness. A better understanding of how evolutionary diversification of taxa contributes to formation of patterns of species richness along environmental gradients is necessary to fully understand spatial variation in biodiversity.
生态学中较为棘手的问题之一是历史过程如何影响当代生物多样性格局。因此，很少有模型被提出。两个推论模型（起源中心、物种形成时间）可用于进行定量预测，以表征热带生态位保守性假说，并将物种多样化描述为从热带地区一个较高分类单元的起源地向外扩散以及随后的物种分支形成过程。从这些模型得出的预测是：（i）物种丰富度朝着较高分类单元分布范围的边缘递减；（ii）分类单元在边缘比在中心更进化；（iii）分类单元的年龄在边缘比在中心更低；（iv）在较高分类单元分布范围的边缘，年龄和进化程度的度量变化较小。我检验了这些预测，以便更好地理解生物多样性中最普遍的格局之一——物种丰富度的纬度梯度的形成。结果表明，对于新大陆叶鼻蝠，这些预测得到了有力支持，并且物种多样化对物种丰富度的纬度梯度有强烈影响。要全面理解生物多样性的空间变化，有必要更好地了解分类单元的进化多样化如何促成沿环境梯度的物种丰富度格局的形成。
