Identifying the mechanisms driving the evolution of breeding systems is one of the central goals in behavioural and evolutionary ecology. Understanding the evolutionary history of species of interest is fundamental to this goal. The objectives of this PhD were, firstly, to investigate the role of sex biases in breeding system evolution among closely-related populations and, secondly, to explore the phylogeographic origins of the plovers, genus Charadrius. The plovers are characterised by extraordinary ecological and behavioural diversity and are therefore ideal study species for this work. Firstly, I investigated the role of sex biases among offspring in breeding system evolution at the population level across four populations of Kentish and snowy plover exhibiting differing levels of male and female care. Theoretical hypotheses link male-biased offspring sex ratios, mating opportunities and male parental care. I present modest support for this hypothesis: male offspring had higher survival levels than female offspring under particular conditions (Chapter 3), and also a tendency for faster growth (Chapter 4) in two populations with predominantly male parental care in contrast to two populations with more balanced parental care roles. Without a phylogenetic framework for the genus Charadrius, evolutionary studies on these diverse shorebirds have been limited in scope. Therefore, secondly, I present the first global, species-level molecular phylogeny of the genus Charadrius and outline their phylogeographic origins. I identified the Northern hemisphere (North America, Europe and Siberia) as the origin of the ancestral Charadrius species between 19.2 and 36.6 million years ago (Chapter 5). I suggest that early evolutionary diversification occurred due to shifts in the range of ancestral Northern hemisphere species in response to global cooling during the Miocene period, leading to colonisation of the Southern hemisphere (Chapter 5). Thirdly, I present the results of a more in-depth phylogeographic study on the Charadrius plovers of Africa. I identified the widespread Kittlitz’s plover (C. pecuarius) as the closest sister species to the ‘critically endangered’ St Helena plover (C. sanctaehelenae) and ‘vulnerable’ Madagascar plover (C. thoracicus; Chapter 6). Additionally, I identified genetic structure consistent with subspecies status among African populations of the white-fronted plover (C. marginatus), three-banded plover (C. tricollaris) and chestnut-banded plover (C. pallidus), but not the Kittlitz’s plover (Chapter 6), with implications for the influence of breeding systems on population-level genetic differentiation. Overall, this thesis both highlights and facilitates several promising new lines of investigation for future research, with the Charadrius plovers as ideal study species (Chapter 7).
|Date of Award||1 Jul 2014|
|Supervisor||Tamas Szekely (Supervisor), Terry Burke (Supervisor) & Patricia L.M. Lee (Supervisor)|