Diversity mechanics: biomechanics as a driver of changes in phenotypic diversification and adaptations in mammals

• Applicant: Brandon Kilbourne, Ph.D.
• Subject Area: Systematics and Morphology (Zoology) ; Ecology and Biodiversity of Animals and Ecosystems, Organismic Interactions
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 471201961

All biological motion is dependent upon the laws of physics. Given this, biomechanical function should leave an imprint upon phenotypic diversification and may act as a driver of adaptive evolution. With a collections focus, the proposed research combines functional morphology with phylogenetic comparative methods to investigate the role of biomechanics in phenotypic diversification in mammals using Carnivora and Caviomorpha, two functionally diverse clades sharing habits for running, climbing, digging, and swimming. The proposed projects link phenotypic variation in these two clades to biomechanical function through finite element and performance landscape modeling. Finite element (FE) modeling estimates how physical structures, such as bones, perform in bearing loads (i.e., forces) by quantitatively estimating the mechanical deformation (strain) and distribution of internal forces (stress) under applied loads. Through FE analysis, my team and I will calculate loading regimes (moments and shear forces) and strain regimes (principal, axial, and shear strains) at 5% increments along the length of the humerus and femur under a set of applied loads. We will then test whether differing locomotor habits within Carnivora and Caviomorpha differ in loading and strain regimes along each bone’s length using both standard and phylogenetic ANOVAs. Furthermore, using a phylogenetically informed test for convergence, we will test whether convergent locomotor habits both within and between Carnivora and Caviomorpha are convergent both in terms of morphology (based upon linear morphometrics) and loading and strain regimes. Performance landscapes re-contextualize the adaptive landscape in terms of biomechanical function. A 3D topographic surface overlapping a morphospace, the different regions of the landscape represent different relative weightings among a set of biomechanical functions measured for the morphologies constituting the morphospace. Constructing a morphospace through geometric morphometrics, we will measure mechanical advantage, bone gracility, load resistance, and bone strength across the morphospace to determine a set of relative weights for these functions across the morphospace. Based upon the location of sampled species in the morphospace, we will then determine if the differing locomotor habits within Carnivora and Caviomorpha occupy regions of morphospace distinguished by differing relative weights of biomechanical functions and whether convergent lineages share similar relative weightings. The combination of finite element and performance landscape modeling will elucidate how morphological diversification is interrelated with biomechanics and will complement joint studies on lineage and trait evolution. The proposed research will create a new template to link biomechanics and morphology in high resolution, with implications going well beyond Carnivora and Caviomorpha.

• DFG Programme: Research Grants