Genus <i>Gobiodon</i>: Taxonomy, Group structure and Relationship with host <i>Acropora</i> coral Habitat Complexity

<p dir="ltr"><i>Gobiodon</i> are a genus of obligate coral dwelling cryptic fish with a mutualistic relationship with scleractinian corals, making them an integral component of coral reef functioning. Despite this, there are significant gaps in knowledge regarding their taxonomy, identification and the relationship between sociality and host coral characteristics. The thesis aimed to address these knowledge gaps by providing formal descriptions of two species of <i>Gobiodon</i>, a cohesive field identification guide to the coral-dwelling fish genus <i>Gobiodon</i> and two studies on the relationship between sociality and the structural complexity of their host corals using experimental and observational studies.</p><p dir="ltr">The literature review provides the background regarding the role of habitat structural complexity on the sociality of animals, in particular, coral dwelling fishes. The first chapter contains a revised description of the genus <i>Gobiodon</i>, formal descriptions of two undescribed species of <i>Gobiodon</i> and taxonomic notes regarding the Southern Pacific Ocean population of the newly described species <i>Gobiodon spadix</i>. This first chapter makes use of morphological and genetic techniques, including morphometrics, meristics, x-ray photography and phylogenetic analysis, to provide supporting evidence for species descriptions. The second chapter aims to enable the efficient identification via inclusion of reviews of the known species of <i>Gobiodon</i>, summarised in a field guide format for coral reef surveys and studies. The guide uses the diagnostic features of each species, known coral hosts, known reef habitats, geography, sociality and known genetic relationships to provide a description of each species alongside photographs and illustrations. Additionally, a field identification key, occurrence table with accompanying map and colour plate of all species illustrations is provided. The third chapter involves the quantification of host <i>Acropora</i> coral complexity characteristics and their relationships with <i>Gobiodon</i> social structure (solitary individual, pair or group). Findings suggest that there is a significant difference between the corals occupied by solitary individuals/pairs and groups. Solitary individuals and pairs were observed in smaller corals with higher levels of structural complexity. However, groups were observed occupying larger corals with lower levels of structural complexity. The fourth chapter focuses on investigating the relationship between <i>Gobiodon quinquestrigatus</i> and the structural complexity of the coral host using a manipulative aquarium experiment. The study utilised 3D printed coral structures to accurately manipulate coral complexity and size to investigate the differences in coral occupancy across individuals of differing social status. The experiment highlighted the importance of social status and coral complexity on coral choice, which has important ramifications for the formation and persistence of sociality under altered environmental conditions.</p><p dir="ltr">Overall, the thesis fills the gaps in knowledge that surround the genus <i>Gobiodon</i> and their relationship with the mutualistic host corals of the genus <i>Acropora</i>. Coral reefs are predicted to be exposed to increased severity and frequency of catastrophic events, such as tropical storms and mass coral bleaching, therefore understanding how <i>Gobiodon</i> and their coral host interaction has never had greater significance than it does in the current day. The thesis adds to a growing body of work on the genus that aids in their continued use as a model species for sociality and potential barometer for coral reef ecosystem health, helping us understand coral reef ecosystems before they are irreversibly altered by the changing nature of the natural world due to human impact.</p>