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Reference : UMR5554-LIOHAU-002
Workplace : MONTPELLIER
Date of publication : Friday, January 01, 2021
Scientific Responsible name : Lionel Hautier
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 March 2021
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Morphological traits that promote the invasion of, and diversification within, new adaptive zones are expected to be more common across the tree of life. Historically, such traits were defined as 'key innovations' since they could explain the evolutionary success of a taxonomic group. Morphologists have embraced the concept of key innovations, and have used it extensively to explain many cases of adaptive radiations. However, the theory behind this concept was strongly criticized due to the lack of evidence demonstrating a causal link between a proposed key innovation and an increase in species diversity. Among mammals, rodents constitute a special case. This 57-million-year-old clade comprises at least 2600 species encompassing an astonishing diversity of forms and showing a markedly uneven distribution of cranial phenotypic variation across families. The ecomorphological diversification of the group has then been considered the result of the acquisition of key cranial and dental innovations, which are considered to be associated with different types of feeding strategies. Strong functional constraints affecting mastication have limited the number of possible evolutionary pathways and promoted convergent evolution, which in return has hampered attempts to establish an intra-ordinal classification of rodents. Such a situation, which explains the past difficulty in classifying rodents based on cranial and dental characteristics, also implies that these features have strong adaptive significance, which then strengthened their image as promoters of diversification and their recognition as key innovations. However, the different components of the masticatory apparatus (i.e. bones, muscles, and teeth) have generally been studied in isolation with little integration of their morphology to function. The overarching goal of this PhD project is to understand whether osteological, dental, and muscular traits evolve independently or synergistically, and whether their evolution influenced diversification of rodent lineages. If cranial features act as key innovations, we predict that functional interactions between traits, rather than traits themselves, will explain why diversity is unevenly distributed among rodent lineages. First, the candidate will focus on assessing the correlation between osteological, muscular and dental characters, to build predictive models of phenotypic integration. Second, he/she will estimate the biomechanical performance of the masticatory apparatus to characterize the morphofunctional link between its components. Third, the candidate will assemble an unprecedented character/taxon matrix for phylogenetic inferences in order to build a morphofunctional model of the masticatory apparatus in some of the earliest representatives of the group.
The candidate will work in interaction with two teams of the Institute of Evolutionary Sciences of Montpellier (ISE-M): the Paleontology team and the Phylogeny and Molecular Evolution team. Several missions abroad in museum collections are envisioned. This thesis project forms part of the DispaRat ANR-funded project, a Collaborative Research Project between the ISE-M (Montpellier) and the PALEVOPRIM (Poitiers), CR2P (Paris) and MECADEV (Paris) laboratories.
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