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RESEARCH PRODUCT

Evolutionary and developmental hypotheses in rodent dentition through time : the adaptive radiation of Arvicolinae (Rodentia)

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The evolution of mammalian dentition is defined by profound morphological modifications as occlusion and heterodonty. Among rodents, characterized by a reduced dental formula, arvicolines have a highly derived dentition, with prismatic and hypsodont molars. The aim of this Ph.D thesis is to explore various morphological innovations through developmental and adaptive aspects. Geometric morphometric methods were used on molars, incisors and mandibles to investigate the dynamics of development and evolution of dentition. A developmental model predicting molar proportions is tested and confirmed for the rodent order; it could be also extended to the premolar. The relationship between dental morphology, in particular molar proportions, and diet is complex, diet being not directly inferred from one morphological trait. Yet, covariations between molars inform on masticatory movement and thus on function. Our results confirmed that morphologies could be understood from a complex combination of historical, functional and developmental constraints. The various structures of the mandible have a complex hierarchical organization. The development of mammalian dentition is controlled by similar processes but through times, mechanisms as heterochrony may lead to a diversification of phenotypes.