Convergent evolution is a phenomenon whereby similar traits evolved independently in not closely related species, and is often interpreted in functional terms. Spines in mollusk seashells are classically interpreted as having repeatedly evolved as a defense in response to shell-crushing predators. Here we consider the morphogenetic process that shapes these structures and underlies their repeated emergence. We develop a mathematical model for spine morphogenesis based on the mechanical interaction between the secreting mantle edge and the calcified shell edge to which the mantle adheres during shell growth. It is demonstrated that a large diversity of spine structures can be accounted for through small variations in control parameters of this natural mechanical process. This physical mechanism suggests that convergent evolution of spines can be understood through a generic morphogenetic process, and provides unique perspectives in understanding the phenotypic evolution of this second largest phylum in the animal kingdom.
Bibliographical noteKAUST Repository Item: Exported on 2020-10-01
Acknowledged KAUST grant number(s): KUK-C1-013-04
Acknowledgements: We thank N. L. Larson (Black Hills Museum of Natural History, Hill City, SD) and J. Thomas (Université de Bourgogne, Dijon, France) for providing us with Fig. 1 C and D, respectively, and P. D. Shipman for helpful exchanges. This publication is based on work supported by King Abdullah University of Science and Technology Award KUK-C1-013-04 (to D.E.M. and A.G.), and a European Commission Framework 7 Reintegration Grant (A.G.). A.G. is a Royal Society Wolfson Research Merit Award recipient.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.