Burning calories, burning ocean: metabolic rate in bivalves as a predictor of extinction selectivity through time and during rapid global warming

Supplementary materials for a manuscript entitled "Burning calories, burning ocean: metabolic rate in bivalves as a predictor of extinction selectivity through time and during rapid global warming" by Gavirneni, Ivany, and Reddin; for submission to Paleobiology.

Abstract: Organismal metabolic rate is linked to environmental temperature and oxygen consumption, and as such, may be a useful predictor of extinction risk during major climate-driven crises. However, metabolic attributes can be quantified in many ways, highlighting differing aspects of organisms’ ecology. Here, we estimate resting whole-body and mass-specific metabolic rates in post-Carboniferous bivalve taxa using body size and seawater paleotemperature to assess how metabolic rate determines survival both during and outside of intervals of rapid climate warming, or “hyperthermals”. Accounting for the effects of geographic range size, we find a pattern of preferential extinction of bivalves with lower total calorific needs, largely determined by smaller body size, consistent with the postulated ramping up of ecosystem energetics over the Meso-Cenozoic. Contrary to expectations, extinction selectivity based on total calorific needs and emphasizing body size does not differ between hyperthermals and other time intervals. However, a higher metabolic rate calculated per gram of tissue, which is more determined by environmental temperature than body size, consistently increases the probability of extinction during hyperthermals relative to baseline conditions, particularly within the paleotropics. In tandem with previously documented patterns of extinction selectivity based on relative activity levels, including motility and feeding style, these results enhance our understanding of the role of metabolic activity through time and during climate-driven extinctions. Standardized by mass, per-gram metabolic rate may represent a useful metric through which the effects of anthropogenic climate change on modern marine faunas can be predicted.