Redpath Museum, McGill University, Montreal, QC, Canada.
Proc Natl Acad Sci U S A. 2010 May 4;107(18):8265-8. doi: 10.1073/pnas.0913645107. Epub 2010 Apr 19.
Beta diversity is an important component of large-scale patterns of biodiversity, but its explicit examination is more difficult than that of alpha diversity. Only recently have data sets large enough been presented to begin assessing global patterns of species turnover, especially in the fossil record. We present here an analysis of beta diversity of a Maastrichtian (71-65 million years old) assemblage of dinosaurs from the Western Interior of North America, a region that covers approximately 1.5 x 10(6) km(2), borders an epicontinental sea, and spans approximately 20 degrees of latitude. Previous qualitative analyses have suggested regional groupings of these dinosaurs and generally concluded that there were multiple distinct faunal regions. However, these studies did not directly account for sampling bias, which may artificially decrease similarity and increase turnover between regions. Our analysis used abundance-based data to account for sampling intensity and was unable to support any hypothesis of multiple distinct faunas; earlier hypothesized faunal delineations were likely a sampling artifact. Our results indicate a low beta diversity and support a single dinosaur community within the entire Western Interior region of latest Cretaceous North America. Homogeneous environments are a known driver of low modern beta diversities, and the warm equable climate of the late Cretaceous modulated by the epicontenental seaway is inferred to be an underlying influence on the low beta diversity of this ancient ecosystem.
β多样性是生物多样性大规模模式的一个重要组成部分，但它的明确考察比α多样性更困难。直到最近，才有足够大的数据集来开始评估全球物种周转率模式，特别是在化石记录中。我们在这里分析了北美的西部内陆地区（覆盖约 1.5 x 10(6)km(2)）的白垩纪恐龙组合的β多样性，该地区与一个内陆海接壤，跨越约 20 度的纬度。先前的定性分析表明这些恐龙存在区域性分组，通常得出存在多个不同动物群区的结论。然而，这些研究并没有直接考虑采样偏差，这可能会人为地降低区域之间的相似性并增加周转率。我们的分析使用基于丰度的数据来解释采样强度，并且无法支持任何关于多个不同动物群的假说；先前假设的动物群划分很可能是采样的人为产物。我们的结果表明β多样性较低，并支持整个北美的晚白垩世西部内陆地区存在一个单一的恐龙群落。均质环境是现代低β多样性的已知驱动因素，而内陆海调节的温暖、稳定的白垩纪气候被推断为这个古老生态系统低β多样性的潜在影响因素。
