Investigating the link between genital evolution and speciation in the millipede Antichiropus variabilis

[Truncated abstract] Taxa displaying high species diversity usually also display elaborate and diverse sexual traits, promoting the idea that sexual selection may be a powerful driver of speciation. However, the links between sexual selection and speciation are contentious, as studies have been largely comparative, and results have been equivocal. Although crucial to understanding the role of sexual selection in speciation, intraspecific studies are rare, as are studies using novel non-model taxa. Millipedes are one group that have been largely neglected in the fields of behavioural ecology and evolutionary biology. The millipede genus Antichiropus displays staggering taxonomic richness in southern Western Australia, and species also display widely-divergent male genital morphology. In this thesis, my primary aim was to use the millipede Antichiropus variabilis Attems, 1911, to test whether directional post-copulatory sexual selection has been responsible for driving divergence in male genital morphology and, more broadly, whether intense sexual selection may contribute to rapid population divergence and ultimately speciation. A comprehensive combination of approaches was used to test the aims of my thesis and thus explore the links between sexual selection, genital evolution and speciation across the geographic range of A. variabilis. Development of laboratory husbandry, rearing and tissue preservation techniques was required to facilitate experimental research (see Chapter 2). Polymorphic microsatellite DNA markers were then isolated and characterised for the first time in a millipede (see Chapter 3), providing a powerful tool and an analytical foundation for further genetic analyses. Extensive biogeographic surveys were conducted throughout the range of A. variabilis (see Chapter 4), enabling detailed population genetic analysis.