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.

形态辐射与大进化模式的解读，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（crinoid）类群为对象，探究了不同分类学尺度（物种、属级）与地理学尺度（区域、生物相（biofacies）、群落）下的形态差异度（disparity）分析结果。本研究基于离散形态特征，分析了来自65个劳伦古陆生物相的421种海百合的形态差异度。在区域与生物相尺度下开展分析时，海百合的形态差异度存在显著差异：尽管区域尺度下海百合的形态差异度存在波动，但各生物相内的平均形态差异度在奥陶纪始终保持稳定，仅在志留纪因形态异常的髓指海百合类（myelodactylid crinoid）的繁盛而出现偏离。分类学尺度的选择在生物相层面未产生显著影响；但在区域尺度下，由于属内物种数量随时间的变化以及单个属内的形态变异程度差异，属级与物种级两种分类尺度会得到不同的分析结果。通过丰度对形态差异度进行加权，可得到一个融合形态特征与群落结构的量化指标。群落尺度下的平均加权形态差异度变化趋势与生物相尺度的差异度曲线相似，但该指标在不同生物相间的变异程度更高。加权与未加权形态差异度比值较低的生物相，呈现出基于气溶胶过滤理论的独特群落结构——这一结构在海百合组合中已有广泛报道。