The shape of penguins in four dimensions : assessing macroevolutionary shifts in a constructional morphology framework : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Zoology at Massey University, Albany Campus, New Zealand
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Date
2022
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Massey University
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Abstract
Describing the morphology of a clade through deep time provides rich insight into the drivers that shaped modern diversity. It is in this context that Adolph Seilacher developed the constructional morphology concept, in order to describe which are the major pressures acting on an organism's morphological appearance. The three components or apices of constructional morphology are the evolutionary history of the organism, the constraints placed on the structure, and the opportunity provided by adaptation. The structure of this thesis is based on the constructional morphology concept with each chapter focusing on the impact of each of the three components of constructional morphology with the scope to provide a novel approach to quantify morphological macroevolution. After introducing concepts of constructional morphology, geometric morphometrics and Bayesian statistics in Chapter 1, Chapter 2 presents an analysis to estimate the historical apex: a phylogenetic analysis based on the synthesis of previous published matrices, as well as a description of the giant fossil penguin Kairuku waewaeroa. The resulting phylogenetic tree indicates that the penguin evolutionary history was characterised by many monophyletic large groups that challenges previous results and indicate that the body plan of extinct penguins could be more diverse than previously thought. Chapter 3 focused on the structural apex, aiming to provide a generalisable Bayesian approach to estimate the size of extinct giant penguins in the context. By measuring the total volume of the femur and the humeral articular facet of the coracoid it was possible to generate two sets of models that together provided novel evidence in favour of reduced body mass estimates for giant penguins when compared with prior published estimates. Moreover, although the two sets of estimates are derived from two distinct features, the body mass estimates from the two models tend to converge, providing confidence in the accuracy of the Bayesian-informed method. Chapter 4 presents and investigation into the impact of adaptation on two separate locomotory modules, the humerus and the tarsometatarsus, using 3D geometric morphometric techniques. Comparing morphological rates of change reveals a steady rate decrease in the humerus and more heterogeneous rates for the tarsometatarsus. Similar results are obtained by estimating the morphospaces for humeri and tarsometatarsi from hypothetical ancestors using a penalized likelihood approach. The synthesis that this constructional morphology framework approach provides highlights the important relationship between shape and size, showing how size can be a driver of morphological innovation. More importantly, the results of this thesis highlight the relevance that constructional morphology still has today, and how it can be integrated into palaeontology and evolutionary biology studies through the use of advanced statistical techniques. A constructional morphology approach is not solely applicable to penguins and may be extended to a broad range of groups of organisms, contributing thus to better understand the underlying forces that shaped the origins of modern biota.
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Figures 1.1 and 1.3 were removed for copyright reasons.
Appendix A was also removed for copyright reasons.
Listed in 2022 Dean's List of Exceptional Theses
Listed in 2022 Dean's List of Exceptional Theses
Keywords
Penguins, Morphology, Dean's List of Exceptional Theses