Hornbills (Aves: family Bucerotidae) are a charismatic group of Palaeotropical birds recognised for their distinctive morphology (casque) and behaviour (nest-sealing). Hornbill diet, habitat use, distribution and social system display pronounced interspecific variation, and their mutualistic interactions with tropical fruits provide vital ecosystem services. A wide range of species of hornbills across the Afrotropics, Indo-Malaya and Melanesia are of conservation concern. However, the evolutionary history of hornbills remains unclear and there are conflicting hypotheses about their origin, tempo of diversification and biogeography. Despite a comprehensive cladistic analysis of phenotypic data, there are unresolved taxonomic uncertainties within the family, and although a gradual accumulation of molecular data has revealed interesting phylogenetic relationships, methodological limitations, and incomplete sampling, has left gaps and produced incongruent results. Hence the evolutionary framework against which to interpret the diversity of this group is incomplete. The aim of this thesis was to construct a well-resolved molecular phylogeny of hornbills, and to use it to address longstanding questions about the evolution and diversification of these remarkable birds. This thesis presents a broad phylogenetic and biogeographic analysis of the family Bucerotidae, based on a coalescence of molecular methods and comparative analyses, largely using historical samples and recently-developed bioinformatic approaches. I provide the first complete species-level molecular phylogeny of hornbills, derived from nuclear adenylate kinase 1 intron 5 and mitochondrial (mtDNA) cytochrome b genes, and also a comprehensive mtDNA phylogeny covering 98% of the taxa, with extensive sampling of Asian geo-isolates. Using these two phylogenetic trees, I sought to determine the tempo of divergence, trace the evolution of traits, identify ancestral areas and colonisation routes, and also calculate genetic divergence. In this part of the work, I stress the importance of (1) using historical samples, (2) calibrating time-trees with fossil and molecular anchor-points, and (3) the use of a complete tree to test models of diversification and reconstruct ancestral states. My findings confirm the monophyly of Bucerotidae, showing nearly distinct African and Asian lineages, with relatively congruent topologies across different phylogenetic methods and genes. In turn, these gene trees were comparable with previous cladistic analysis based on phenotypic data. As a result, I was able to resolve some taxonomic issues and propose generic changes. Comparative analyses of social behaviour revealed that cooperative breeding is an ancestral trait, and its evolution in hornbills (in contrast with some other taxa) is associated with stable environments in combination with frugivory, territoriality and reduced body size. Analysis of the evolution of diet with diversification showed that the shift to frugivory from faunivorous African ancestors influenced the rapid diversification of Afro-Asian forest hornbills, facilitated by their preference for humid forests and mutualistic interactions with , hornbill-dispersed fruits (HDF). This dispersal of frugivorous lineages via the Palaeotropical Biotic Interchange promoted colonisation of Asia, with Sundaland being the centre of radiation for continental and insular Asian species. The gradual eastward colonisation from India to Melanesia matches palaeo-tectonic events that allowed dispersal across Huxley's, Wallace's and Lydekker's lines, and was congruent with historical biogeography of some HDFs. Finally, I used a combined analysis of genetic divergence and a standard scoring system for phenotypic data of Asian geo-isolates to provide evidence for quantitative delineation of species and propose changes in conservation status. My findings reveal the evolutionary history of horn bills from their emergence in the Late Oligocene from African origins, with a switch to frugivory influencing successful colonisation of hornbills and HDFs in Asian forests, which combined to promote sociality. Overall, this thesis demonstrates that access to novel environments and innovations to ecological niche facilitate rapid diversification in an avian lineage, and that this process is further promoted by the interplay of these birds in complex mutualistic interactions with their food, as well as palaeo-climatic and palaeo-tectonic changes.

Thesis (M.S.)--University of North Carolina at Greensboro, 2005. / Title from PDF title page screen. Advisor: David L. Remington; submitted to the Dept. of Biology. Includes bibliographical references (p. 51-55).

Thesis (M.S.)--University of North Carolina at Greensboro, 2005. / Advisor: David L. Remington; submitted to the Dept. of Biology. Includes bibliographical references (p. 51-55).

Thesis (M. Phil.)--University of Hong Kong, 2010. / Includes bibliographical references (p. 178-187). Also available in print.

The genus Cochlearia is a taxonomically complex genus with a circumpolar distribution. In common with many other post-glacial colonisers it exhibits complex patterns of morphological and ecological variation. The genus has been the subject of continued taxonomic controversy, especially within the species complex C. officinalis s.l. The focus of this study was to investigate whether the three rare putative endemic Cochlearia officinalis s.l. taxa in Britain: C. micacea, C. officinalis subsp. scotica and C. atlantica were sufficiently distinctive to warrant endemic species or taxon status at any rank. Furthermore, to make conservation recommendations for the species complex based on the outcome of this investigation. The patterns of differentiation in Cochlearia were studied to gain insight into the processes that have driven morphological and ecological diversification in the group. The six putative taxa in Cochlearia officinalis s.l. were considered in this study: C. officinalis s.s., C. officinalis subsp. scotica, C. pyrenaica subsp. pyrenaica, C. pyrenaica subsp. alpina, C. atlantica and C. micacea. Samples of C. danica, a member of the wider genus Cochlearia, were also included for comparison. The samples were screened for variation in AFLP fragments, morphological characters and chloroplast haplotypes. This is the first study focussed on the British Cochlearia to use the amplified fragment length polymorphism (AFLP) technique. Many qualitative morphological characters differences between populations were maintained in cultivation under standard conditions. Variation in some quantitative morphological characters was significantly different between taxon groups. The morphological characters combined did not distinguish between taxonomic groups. Variation was found in samples from the uplands only. Although there were three chloroplast haplotypes all but 6 out of 96 samples had the same haplotype and the chloroplast was not taxonomically informative. The AFLP data did not vary significantly between taxonomic groups, ploidy levels, habitats or geographical regions. There was significant AFLP variation between populations. The morphological and ecological diversity present among populations of Cochlearia officinalis s.l. in Britain is most likely to result from local ecotypic differentiation. The variation in Cochlearia officinalis s.l. could not be divided satisfactorily into taxa of species rank and so specific conservation of taxa within the complex is not recommended. Instead the maintenance of Cochlearia diversity can be achieved by the continued protection of the habitats in which the ecotypes grow.

Thesis (Ph. D.)--Brandeis University, 2009. / "UMI:3369218." MICROFILM COPY ALSO AVAILABLE IN THE UNIVERSITY ARCHIVES. Includes bibliographical references.