BIOGEOGRAPHIC VARIATION IN MORPHOLOGICAL DISPARITY OF STROPHOMENIDA (BRACHIOPODA) (Invited Presentation)

The Strophomenida is an order of brachiopods that originated in the Ordovician and rapidly diversified during two evolutionary radiations, first during the Great Ordovician Biodiversification event, and second, during the Silurian recovery from the Late Ordovician mass extinction event. The group is widespread throughout the Ordovician, with several cosmopolitan genera.

The Strophomenida provides an excellent study taxon to evaluate how ecological preference, biogeography, and evolution interact with each other throughout deep time. At the Late Ordovician mass extinction, this group experienced a morphological bottleneck, turnover in abundant families, and selectivity against taxa with small geographic ranges. Linking the biogeographic, taxonomic, and morphological patterns in biodiversity will provide insight into feedbacks between evolution, morphological disparity, and filling of ecological space. Here we ask whether there is a biogeographic signal to clade morphology, namely are cosmopolitan families more morphologically disparate than their endemic relatives?

To address this question, we conduct a PCO analysis to study the morphospace of character data from the recently revised composite tree for Strophomenida. This morphospace data is compared with ancestral range reconstructions from biogeoBEARS and occurrence data from the Paleobiology database to study how morphospace varies spatially and temporally. We use these data to explore how morphospace occupation of Strophomenida changed across paleocontinents and over the radiations experienced by the order. We also assess whether cosmopolitan or endemic taxa experience different patterns of disparity.

Results of this study offer insight into mechanisms that drove extinction, radiation, and turnover within Strophomenida. This is important for understanding the links between ecology, morphology, and evolutionary history and developing a more holistic understanding of the effects of extinction and origination.