Department of Geology, University of Cincinnati, Cincinnati, Ohio, United States of America.
PLoS One. 2012;7(8):e40472. doi: 10.1371/journal.pone.0040472. Epub 2012 Aug 3.
For present-day biotas, close relationships have been documented between the number of species in a given region and the area of the region. To date, however, there have been only limited studies of these relationships in the geologic record, particularly for ancient marine biotas. The recent development of large-scale marine paleontological databases, in conjunction with enhanced geographical mapping tools, now allow for their investigation. At the same time, there has been renewed interest in comparing the environmental and paleobiological properties of two broad-scale marine settings: epicontinental seas, broad expanses of shallow water covering continental areas, and open-ocean-facing settings, shallow shelves and coastlines that rim ocean basins. Recent studies indicate that spatial distributions of taxa and the kinetics of taxon origination and extinction may have differed in these two settings. Against this backdrop, we analyze regional Genus-Area Relationships (GARs) of Late Cretaceous marine invertebrates in epicontinental sea and open-ocean settings using data from the Paleobiology Database. We present a new method for assessing GARs that is particularly appropriate for fossil data when the geographic distribution of these data is patchy and uneven. Results demonstrate clear relationships between genus richness and area for regions worldwide, but indicate that as area increases, genus richness increases more per unit area in epicontinental seas than in open-ocean settings. This difference implies a greater degree of compositional heterogeneity as a function of geographic area in epicontinental sea settings, a finding that is consistent with the emerging understanding of physical differences in the nature of water masses between the two marine settings.
对于现代生物群，在给定区域中物种的数量与该区域的面积之间存在密切关系。然而，迄今为止，这些关系在地质记录中的研究非常有限，尤其是对于古代海洋生物群。最近，大规模海洋古生物学数据库的发展，结合增强的地理绘图工具，现在允许对这些关系进行研究。与此同时，人们对比较两种广泛的海洋环境的环境和古生物学特性重新产生了兴趣：大陆边缘海，覆盖大陆地区的广阔浅水区域，以及面向开阔洋的浅海架和海岸线。最近的研究表明，在这两种环境中，分类群的空间分布以及分类群起源和灭绝的动力学可能有所不同。在此背景下，我们使用古生物学数据库中的数据，分析了白垩纪海洋无脊椎动物在大陆边缘海和开阔洋环境中的区域属-面积关系（GAR）。我们提出了一种新的方法来评估 GAR，当这些数据的地理分布不均匀时，这种方法特别适用于化石数据。结果表明，全球范围内属丰富度和面积之间存在明显的关系，但表明在大陆边缘海中，随着面积的增加，每个单位面积的属丰富度增加幅度大于开阔洋环境。这种差异意味着在大陆边缘海环境中，地理区域内的组成异质性程度更大，这一发现与对两种海洋环境中水体性质的物理差异的理解相一致。
