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（morphologic radiations）与大进化模式（macroevolutionary patterns）的解读，有赖于研究中分类尺度与地理尺度的先验选择（a priori choices）。本研究针对奥陶纪（Ordovician）至早志留世（Early Silurian）的海百合（crinoids）类群，对不同分类尺度（物种、属级）与地理尺度（区域、生物相、群落）下的形态差异度分析（disparity analysis）结果进行了探讨；研究采用离散形态特征（discrete morphologic characters），对源自65个劳伦生物相（Laurentian biofacies）的421种海百合开展了形态差异度（disparity）测算。在区域尺度与生物相尺度下分析时，海百合的形态差异度存在显著差异；无论区域尺度下海百合形态差异度的波动情况如何，各生物相内部的平均形态差异度在奥陶纪始终保持稳定，仅在志留纪因形态怪异的髓指海百合类（myelodactylid crinoids）的繁盛而出现偏离。在生物相尺度下，分类层级的选择并不会对分析结果产生影响，但在区域尺度下，由于不同时期内每属所含物种数以及单个属内的形态变异量存在差异，物种级与属级两种分类尺度会得到不同的分析结果。按丰度加权的形态差异度是一种结合形态学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的变化模式与生物相尺度下的差异度曲线相似，但该指标在不同生物相间的波动幅度更大；加权差异度与未加权差异度比值较低的生物相，呈现出基于气溶胶过滤理论（aerosol filtration theory）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。