Testing for allocation strategies and evolutionary tradeoffs in the bivalve shell.

This article focuses on analyzing evolutionary allocation strategies and potential tradeoffs in marine bivalves by quantifying volumetric components of their shells and internal cavities. Using 3D scans of 385 valves from 339 species in the Florida Keys, the study defines an allocation space based on volumes of the internal cavity (housing soft tissues), the base shell, and shell sculpture (ornamentation). Results show that most species allocate body volume primarily between the internal cavity and base shell, with shell sculpture generally comprising a small proportion; notably, species with thicker shells tend to have more prominent sculpture, indicating a structural rather than a tradeoff relationship. The study finds no significant influence of outer shell mineralogy or microstructure on these allocation patterns and suggests that this morphospace framework can inform understanding of bivalve macroevolutionary dynamics and energetics from fossil shells.