QUANTITATIVE, TRAIT-BASED APPROACHES FOR INVESTIGATING NICHE EVOLUTION AND PALEOCOMMUNITY RESTRUCTURING: CASE STUDIES FROM THE CRINOID FOSSIL RECORD

Marine paleocommunities have changed substantially throughout the history of life in terms of taxonomic composition, resource utilization, functional diversity, vertical complexity, and structure. As a result, a central challenge in the study of evolutionary paleoecology is to quantify these features within paleocommunities and identify their evolutionary drivers across taxonomic, spatial, and temporal scales. However, many fundamental components of paleocommunities, such as ecological niches, are difficult to quantify and investigate in the fossil record due to their complex nature. Likewise, many evolutionary mechanisms responsible for driving ecological change within paleocommunities can only be fully recognized and investigated within a phylogenetic framework.

Here, I discuss the value of applying quantitative approaches to ecomorphological trait data at the community level, emphasizing changes in niche occupation and phylogenetic community structure of Ordovician crinoids. Crinoids are a model study system for this work as they preserve abundant ecological information in ecomorphological traits, which can be analyzed with multivariate approaches to quantify ecological niche space in multiple dimensions. In addition to characterizing realized niches, this methodology allows shifts in niche space occupation through time to be detected, and ecomorphological data are used to calculate ecological disparity between paleocommunities across multiple taxonomic scales. Finally, incorporating phylogenetic comparative approaches allows phenomena like niche conservatism versus convergence to be recognized at the community scale, which permits further investigation of the generating processes and evolutionary pressures responsible for niche evolution and paleocommunity restructuring. Although these methods are relatively common in studies of modern communities, they are comparatively rare in paleocommunity analysis and thus represent a promising area for future investigations of communities in deep time.