Biogeographic Consequences of Eurytopy and Stenotopy Among Marine Bivalves and Their Evolutionary Significance

Abstract

Infaunal bivalves able to live in depths of 1 meter or less have significantly wider geographic distributions than infaunal bivalves restricted to deeper waters (not including deep-sea species). Shallower species tolerate a wider range of environmental conditions and probably have longer-lived larvae than species limited to depths greater than 1 meter. As a result of differences in geographic distribution, species able to live as shallow as 1 meter should be less likely to speciate or go extinct than species restricted to deeper waters. Low-diversity species associations (⩽ 1 meter) should therefore also be evolutionarily more stable than high-diversity (>1 meter) associations. These predictions are supported by evidence from the fossil record.