Abstract
Operating on higher temporal and taxonomic scales, macroevolution seeks to understand the biodiversity of the world through the lens of great change. Phylogenetic diversity, morphological disparity and niche adaptation are core tenets of macroevolution, and their interactions are of great interest. In the 21st Century, analytical methodologies and high-dimensional datasets have become the leading macroevolutionary approaches and allow researchers to return to fundamental hypotheses posited in the years since Darwin. Seabirds are a highly diverse and speciose group that occupy ranges that span from the equator to the poles. By leveraging the latest methodologies and techniques, I return to the core tenets of macroevolution to shed new light on old problems using seabirds. Gentoo penguins have a circumpolar distribution and have been reported to have significant morphological and genetic variation across this range. Here I show that four distinct populations of gentoo penguins (Iles Kerguelen, Falkland Islands, South Georgia, South Shetlands/Western Antarctic Peninsula) are genetically and morphologically distinct from one another and update the taxonomy to reflect these divergences. The results further highlight the importance of reassessing species boundaries as methodological advances are made, particularly for taxa of conservation concern. Alongside several wing adaptations, albatrosses and other Procellariiformes have augmented rhamphothecas constructed of several jointed keratinous plates rather than a single structure. Using 3D reconstructions of upper bills, I investigated the range of morphologies present within twelve species of albatross and the relative predictive strength of intrinsic (size & species assignment) and extrinsic (diet) factors. Species are separated both in shape and size reducing niche overlap and simple dietary classifications can distinguish bill shapes. Size is relatively unimportant when allometry models are considered with species assignment accounting for ten times more variation in bill shape. The results show that both intrinsic and extrinsic factors should be considered when understanding morphological evolution. Diving as a foraging behaviour is displayed across waterbirds but the history of the trait has rarely been investigated in a phylogenetic context. I find that diving has evolved numerous times but the transition to diving is irreversible. The transition to diving is accompanied by a shift in disparity as diving forms evolve towards a heavier body mass, while concurrently occupying new diversification regimes that exhibit increased extinction rates. Our findings highlight the vulnerability of highly specialised lineages during the ongoing sixth mass extinction.Jointly, these analyses show that there is considerable interaction between the different elements comprising macroevolution and that these linkages are complex, even when viewed through simple questions. Only by considering all aspects of macroevolution and utilising the latest techniques can we start to comprehend the patterns and trends in biodiversity.
| Date of Award | 27 Mar 2024 |
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| Original language | English |
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| Supervisor | Matthew Wills (Supervisor), Nicholas Priest (Supervisor) & Jane Younger (Supervisor) |