Data from: How species longevity, intraspecific morphological variation, and geographic range size are related: a comparison using late Cambrian trilobites

Phenotypic variation is fundamental to evolutionary change. Variation not only evinces the connectivity of populations but it is also associated with the adaptability and evolvability of taxa. Despite the potential importance of morphological variation in structuring evolutionary patterns, little is known about how relative differences in intraspecific morphological variation and its geographic structure are linked to differences in species longevity. This study offers a novel combination of analyses that reveal the quantitative relationships among intraspecific variation, geographic range size and duration in the fossil record using late Cambrian trilobites. Results show that geographic range size and duration are positively correlated. Surprisingly, longer lived species tend to have less intraspecific variation. Phylogenetic effects were also explored and found not to determine the association between these variables. However, the distribution of geographic range sizes shows strong phylogenetic signal. In light of previous work, one possible explanation for these results is that species with shorter durations have comparatively higher rates of morphological evolution, reflected in higher phenotypic variation overall.

表型变异（phenotypic variation）是进化改变的核心基础。变异不仅能够体现种群的连通性，还与各分类群的适应性及进化潜能密切相关。尽管形态变异在塑造进化格局中具有潜在重要性，但目前学界对种内形态变异的相对差异及其地理结构，如何与物种存续时长的差异相关联仍知之甚少。本研究采用新颖的联合分析方法，以晚寒武世三叶虫为研究对象，揭示了种内变异、地理分布范围大小与化石记录存续时长三者间的定量关系。研究结果显示，地理分布范围大小与化石记录存续时长呈正相关关系。令人意外的是，存续时长更长的物种，其种内变异水平往往更低。本研究还探讨了系统发育效应，发现其并未决定上述变量间的关联关系。不过，地理分布范围大小的分布模式却表现出显著的系统发育信号。结合既往研究，对上述结果的一种可能解释是：存续时长较短的物种，其形态进化速率相对更高，这一点整体体现为更高的表型变异水平。