Molecular Evolutionary Studies of New Zealand Birds

Abstract

This thesis reports the use of molecular sequence information to investigate the evolution of avian fauna in New Zealand and elsewhere. Mitochondrial DNA sequences were amplified from extant and preserved specimens of up to 3,500 years in age using the polymerase chain reaction. Sequences from different taxa are compared in order to examine phylogenetic, systematic, and ecological questions that range from the evolution of modern birds approximately 150 million years ago, to current conservation issues in New Zealand. New Zealand is shown to be a valuable source of evolutionary information because of the combination of the unique biota derived from the Cretaceous super-continent Gondwana and prolonged period of isolation with an absence of non-flying land mammals. However, the lack of a terrestrial vertebrate fossil record has limited evolutionary studies of the unique endemic biota, and morphological convergence and specialisation has complicated systematic studies. Molecular information is shown to be capable of providing a temporal scale for evolution in New Zealand and to allow the investigation of systematic relationships of endemic avian taxa without difficulties associated with morphological analyses of island taxa. Molecular data is interpreted to reveal several previously unexpected evolutionary events within New Zealand. Mitochondrial DNA sequence data is used to suggest that the two endemic New Zealand ratite families, the moa (Dinornithidae) and kiwi (Apterygidae), represent two separate invasions of New Zealand, and that they are not monophyletic within ratites. Furthermore, two different mitochondrial gene sequences are used to suggest that a catastrophic geological event in the Oligocene reduced the mitochondrial genetic diversity of moa, kiwi, and New Zealand wren (Acanthisittidae) taxa. This restriction is hypothesised to result from a prolonged period of limited population size due to a decrease in land size and physical relief. The implications for genetic diversity, and possibility of testing this hypothesis in other endemic taxa are discussed. The fossil record of penguins in New Zealand is used to calibrate genetic distances observed between mitochondrial sequences of procellariiforms, ratites, and psittaciforms, and representatives of seven avian orders. The calibrated dates of divergence reveal that the modern orders of birds radiated prior to the Cretaceous/Tertiary boundary (65 Ma), and that radiations within orders such as psittaciforms had also begun by that time. Uncertainties associated with the estimation of genetic distances between sequences were found to limit resolution and statistical significance of the findings. The use of molecular data from preserved specimens is shown to be especially valuable for the analysis of evolutionary relationships of extant and extinct island biota. Ancient DNA sequences are used to complement morphological studies and allow possible coevolutionary and paleoecological relationships between endemic New Zealand birds and flora to be examined. In addition, ancient DNA sequences are used to review the taxonomic and phylogenetic relationships of extinct and extant moa and New Zealand wren taxa. The appropriate techniques and concerns associated with the use of ancient DNA sequences are extensively reviewed.