Quantifying morphological change during an evolutionary radiation of Devonian trilobites

The fossil record provides an important source of data on adaptive radiations, and indeed some of the earliest theoretical insights on the nature of these radiations were made by paleontologists. Here we focus on the diverse Devonian Metacryphaeus group calmoniid trilobites, known from the Malvinokaffric Realm; these have been considered a classic example of an adaptive radiation preserved in the fossil record. A geometric morphometric analysis is used in conjunction with phylogenetic and biogeographic patterns and data on speciation rates. Patterns of morphological change are quantified using ancestral character state reconstruction during speciation events in order to assess the role ecological and geographical factors may have played in mediating this radiation. No significant differences were found between the amount of morphological change that occurred during speciation events when ancestors and descendents were in the same area as opposed to when they occupied different areas. Fu...化石记录是适应辐射（adaptive radiations）研究的重要数据来源，事实上，古生物学家最早针对这类辐射演化的本质提出了相关理论见解。本研究聚焦于产自马尔维诺-卡法里克域（Malvinokaffric Realm）的多样性泥盆纪Metacryphaeus属卡尔蒙虫科（calmoniid）三叶虫类群，该类群被视作化石记录中保存的适应辐射经典案例。本研究将几何形态测量学分析（geometric morphometric analysis）与物种形成速率（speciation rates）数据、系统发育及生物地理模式相结合。研究通过物种形成事件中的祖先特征状态重建（ancestral character state reconstruction）对形态变化模式进行量化，以此评估生态与地理因素在调控本次辐射演化过程中所发挥的作用。研究发现，当祖先类群与后裔类群分布于同一区域时，物种形成事件期间发生的形态变化量，与二者分布于不同区域时并无显著差异。Fu...