Cox, SC; (2013) Molecular Systematics and Diversification of African Zosteropidae (Aves: Passeriformes). Doctoral thesis , UCL (University College London).

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Abstract

The hyper-diverse avian family Zosteropidae (~100 species) is renowned for its exceptional colonising ability and rapid recent diversification. The genus Zosterops dominates within the family, including over 70% of all recognised species, and is notorious for the phenotypic uniformity that has traditionally made designation of taxon boundaries within the genus difficult. While the last decade has seen an abundance of research focusing on colonisation abilities and speciation patterns of insular taxa, relationships between continental forms, specifically mainland African taxa, remain subject to great uncertainty. This thesis focuses on uncovering the relationships, origin and evolutionary history of African Zosteropidae. Chapter 1 introduces the family Zosteropidae, reviews the current literature that is based predominantly on insular systems. In introducing the African Zosteropidae complex, this chapter highlights questions associated with this group and presents the aims of the thesis. Chapter 2 focuses in on one of the most geographically complex areas within the African system, to explore the relative importance of past climatic fluctuations as a driver of diversification in Zosterops endemic to the isolated montane massifs of East Africa. Results provide the first molecular assessment of mainland African Zosteropidae and are used to examine alternative models of speciation. A dated molecular phylogeny demonstrates that divergence within African Zosteropidae is very recent (<5Ma) coinciding with periods of climatic instability during the Plio-Pleistocene. Furthermore, the non-monophyly of mainland taxa, specifically the polyphyletic nature of Z. poliogaster, leads to the rejection of a widely held assumption that the montane endemics of East Africa are relics of a previously widespread population. Instead results provide evidence for evolutionary model based on ancestrally adaptive populations. Chapter 3 attempts to further investigate relationships within the East African Zosterops and explores the usefulness of amplified fragment length polymorphism (AFLPs) in revealing inter- and intra-specific relationships. Resolution of relationships across the AFLP phylogeny is generally poor which is attributed to the low information content of the AFLP matrix generated. Bayesian hypothesis testing failed to provide support for various topological constraints tested and consequently this study was unable to confirm or reject the non-monophyly of East African montane endemics. Chapter 4 builds upon the molecular phylogeny of Chapter 2, by substantially increasing the taxonomic sampling of African species using DNA obtained from museum specimens. The use of both archive and fresh material enabled the largest genetic assessment of western Zosteropidae to date. Extensive sampling across Sub-Saharan Africa, the Indian Ocean region, the Arabian Peninsula and the Gulf of Guinea region reveals six major clades within the African Zosteropidae complex. Results confirm the widespread non-monophyly of mainland African species rendering current taxonomic arrangements invalid. GMYC (General mixed Yule-coalescent) analysis recovers 14 distinct evolutionary lineages within the African Zosteropidae system and provides a framework for further work using model-based species delimitation approaches. Finally, Chapter 5 draws together key findings from Chapters 2-4, and reviews how this work advances our understanding of the African Zosteropidae system. This chapter also highlights new gaps in our understanding of the western Zosteropidae and discusses several areas for future research.

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