Sylvain Gerber PhD thesis

Morphological disparity at ontogenetic and evolutionary scales: examples from cephalopods

 

Summary

The approaches developed in this work are intended to introduce a developmental perspective into studies of morphological disparity. The consideration of the ontogenetic dynamics that leads to adult phenotype is an important step in the understanding of morphospace occupation and structuring. The first approach examines the construction of developmental morphospace – i.e. carrying ontogenetic information – within which juvenile and adult disparities are contrasted. Combined with the analysis of allometric trajectories, this approach allows heterochronic inferences and the detection of adult disparity patterns driven by developmental constraints. Also, the concepts of allometric space and allometric disparity are introduced. These supply a dynamic characterization of ontogenies, of their evolution, and incorporate the standard analytical toolkit of disparity studies. Stochastic and deterministic models of morphological and developmental diversification are used to test the relevance of these different developmental proxies and assess their connections. All the approaches studied are illustrated using case studies based on extant and fossil cephalopods. They outline the need for a more balanced view of intrinsic and extrinsic factors as potential explanatory processes of the patterns observed, and confirm the role of development in macroevolution.

 

Keywords

macroevolution, paleobiology, morphological disparity, morphospace, ontogeny, allometry, morphometrics, simulations, cephalopods