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| Randau da Costa Carvalho, M. | |
| Drivers and constraints of shape evolution in the vertebral column of felids (Felidae, Carnivora) | |
| 2017 Full Book | |
Morphological studies of the skull and limbs of tetrapods are common in the literature. Nonetheless, the vertebral column has been comparatively neglected, and research shows a bias towards developmental and genetic approaches. Still, these studies have highlighted the unusual uniformity in vertebral count across mammals, unlike the great variation in vertebral numbers observed in other tetrapod clades. This meristic constraint has been suggested to drive higher regionalisation in the mammalian axial skeleton, with adaptation to discrete niches happening primarily through modification of vertebral form rather than changes in numbers. Living species of the mammalian family Felidae are an ideal group for vertebral studies as all taxa present the same count of 27 presacral vertebrae but vary in ecological specialisations and body mass. In this thesis, I explore the morphological evolution of the presacral vertebral column by, first, investigating ecological and phylogenetic influences on presacral vertebral shape, and then, examining patterns of vertebral trait covariation with an evolutionary developmental perspective. My results show clear regionalisation of vertebral column shape and function. Specifically, a highly integrated region between the diaphragmatic vertebra and the last lumbar (i.e., T10 - L7) shows the highest levels of ecological specialization, and potentially higher evolvability, contrasting with a phylogenetically conserved neck region. I found strong support for a widespread two-module model of intravertebral shape based on developmental origins of vertebral components, and this analysis also provided an empirical example of phenotypic integration promoting higher morphological disparity. Exceptions to this model are at boundaries of large vertebral modules and suggest functional overprinting of developmental patterns. Further, I demonstrated the presence of modularity at the organismal level, with decoupling of the vertebral column as a whole from other skeletal structures. Combined, the work presented in this thesis demonstrates that axial evolution across Felidae reflects both developmental constraints and functional specialisation by concentrating shape change within distinct evolutionary modules. This thesis provides a foundation for further study of vertebral columns combining both functional and developmental perspective |
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