HOW DOES NICHE EVOLUTION CONTRIBUTE TO DIVERSIFICATION? A TEST USING ECOLOGICAL NICHE MODELLING TO EXAMINE LAURENTIAN BRACHIOPODS DURING THE ORDOVICIAN

The Ordovician was a complex interval of Earth history, characterized by explosive biotic diversification coupled with dramatic environmental changes including climatic shifts and sea level fluctuations. To understand the impact of earth system changes on biodiversity, it is necessary to investigate the temporal correlation between species ecological responses and changing environmental factors. This project addresses this complex relationship by using ecological niche modelling (ENM) to quantify patterns in Laurentian brachiopod niche occupation over the course of multiple environmental changes in the Ordovician.

ENM analysis requires taxon occurrence and environmental layer data. Brachiopod occurrence data were downloaded from the Paleobiology and iDIGBio Databases. Environmental layers were created using detailed stratigraphic records published in relevant literature. Niche models were generated for stage-level time slices over the entire Ordovician Period using Maxent. For genera that could be modeled in multiple time slices, niches were compared among distinct intervals. The degree of similarity between models of adjacent time slices was analyzed, and patterns of niche stability versus evolution were compared with contemporaneous local and global environmental changes.

Patterns in niche occupation reveal that rates of niche evolution differed during intervals of abiotic versus biotic environmental change. Similarly, trends in niche evolution differ between generalists and specialist taxa, particularly in response to rapid competitive pressures. The results of this study indicate that species respond differently based on different types and rates of environmental change, and suggest that major environmental changes in the modern can have similar long-term biotic impacts.