58-9 Increased polymorphism is associated with heightened extinction across the end-Cretaceous event in cheilostome bryozoans

Session: Future Leaders in Paleontology

Presenting Author:

Authors:

Abstract:

Division of labor is associated with ecological success in colonial animals such as eusocial insects and bryozoans. Given this association, we might expect division of labor to buffer against extinction during intervals of large scale climatic and environmental change. Here, we compile and analyze a global dataset of fossil colonial animals, cheilostome bryozoans, to test whether division of labor is associated with biotic shifts and extinction across the end-Cretaceous mass extinction (66 Ma). Cheilostome colonies have a wide range of division of labor, reflected by their different body types, termed polymorphs. The pre- and post-extinction biotas of cheilostome bryozoans were not significantly different in their degrees of polymorphism. However, taxa with more polymorph types showed heightened extinction through the end-Cretaceous event. Colony energetics may have played a role in extinction outcomes: colonies with more polymorphism have reduced numbers of feeding in colonies, requiring higher per-capita acquisition of resources. Thus, even typically advantageous traits like division of labor can become liabilities in times of widespread environmental perturbation, revealing how selective regimes can shift rapidly during mass extinction.

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-8726

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