Data from: Comparing taxonomic and geographic scales in the morphologic disparity of Ordovician through Early Silurian Laurentian Crinoids

Interpretations of morphologic radiations and macroevolutionary patterns are dependent on a priori choices of taxonomic and geographic scales of study. The results of disparity analysis at varying taxonomic (species and genus) and geographic (regional, biofacies, and community) scales are examined in a study of Ordovician though Early Silurian crinoids. Using discrete morphologic characters, we examined the disparity of 421 crinoids from 65 Laurentian biofacies. Crinoid disparity differs when analyzed at the regional and biofacies levels. Regardless of fluctuations in regional crinoid disparity, average within-biofacies disparity was static throughout the Ordovician, deviating only during the Silurian because of the proliferation of the morphologically aberrant myelodactylid crinoids. The choice of taxonomic level does not have an effect at the biofacies level. However, at the regional level, the two taxonomic scales (genus and species) can produce different results because of variation in the number of species per genus through time and the amount of morphologic variation within individual genera. Weighting disparity by abundance provides a metric combining morphology and community structure. Average weighted disparity at the community level showed patterns similar to that of the biofacies-level disparity curve, but this metric has a greater degree of variation between biofacies. Biofacies with a low ratio of weighted to unweighted disparity display the distinctive community structure (based on aerosol filtration theory) that is often reported in crinoid assemblages.对形态辐射与宏观演化模式的解释，依赖于研究中分类学与地理学尺度的先验选择。本研究以奥陶纪至早志留世的海百合类群为对象，探讨了不同分类（物种级、属级）与地理（区域、生物相、群落）尺度下的形态分异度（disparity）分析结果。研究团队利用离散形态特征，对采自65个劳伦西亚生物相的421种海百合开展了形态分异度分析。结果显示，海百合的形态分异度在区域与生物相尺度下存在显著差异：尽管区域尺度下海百合的形态分异度存在波动，但各生物相内的平均形态分异度在奥陶纪始终保持稳定，仅在志留纪因形态怪异的髓指海百合（myelodactylid）类群的繁盛而出现偏离。在生物相尺度下，分类学等级的选择不会对分析结果产生影响；但在区域尺度下，由于不同时代下每属所含物种数量以及单属内的形态变异量存在差异，属级与物种级两种分类尺度会得到截然不同的结果。通过丰度加权的形态分异度指标，可同时整合形态特征与群落结构信息。群落尺度下的平均加权形态分异度模式，与生物相尺度下的形态分异度曲线相似，但该指标在不同生物相间的变异程度更高。加权分异度与未加权分异度比值较低的生物相，呈现出基于气溶胶过滤理论的典型群落结构——这也是海百合组合中常见的群落结构特征。