CE02 - Terre vivante

Skull trait interactions and macroevolutionary dynamics of the adaptive radiation of rodents. – DispaRat

Submission summary

Phenotypic disparity and species diversity are the hallmarks of biodiversity. 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 innovations, which are considered to be associated with different types of feeding strategies. Several dental characteristics associated either with modifications of the chewing movements or with dietary adaptations, were also proposed as a key explanatory factor to major diversification events. 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 the DispaRat project is to understand whether osteological, dental, and muscular traits evolve independently or synergistically, and whether their evolution influenced diversification of rodent lineages. We will employ a holistic, integrative approach combining state-of-the-art methods of morphological quantification with the latest macroevolutionary methods to address the following hypotheses: Hypothesis 1 – Osteological, dental, and muscular traits are highly interdependent functionally and characterize dietary habits and lifestyle. By exploring the dynamics of the relationships between morphological and mechanical diversity, we predict that the demand of evolving different ecological strategies will explain cohesive suites of morphological traits. Hypothesis 2 - Specific associations of cranial features act synergistically as a key innovation to promote diversification of rodents. 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. We will take a four-step approach to testing these two hypotheses. First, we will focus on assessing the correlation between osteological, muscular and dental characters, to build predictive models of phenotypic integration (WP1). Second, we will estimate the biomechanical performance of the masticatory apparatus to characterize the morphofunctional link between its components (WP2). Third, we 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 (WP3). Finally, we will explicitly test if some functional interactions between traits, or traits themselves, can trigger diversification in rodent groups (WP4).

Project coordination

Lionel Hautier (Institut des Sciences de l'Evolution de Montpellier)

The author of this summary is the project coordinator, who is responsible for the content of this summary. The ANR declines any responsibility as for its contents.


ISEM Institut des Sciences de l'Evolution de Montpellier
CR2P Centre de recherche sur la paléobiodiversité et les paléoenvironnements
MECADEV Mécanismes Adaptatifs et Evolution

Help of the ANR 464,918 euros
Beginning and duration of the scientific project: February 2021 - 48 Months

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