School of BioSciences - Theses
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ItemThe bryophyte flora of Lord Howe Island: taxonomy, diversity and biogeography( 2018)Before this study the known Lord Howe Island bryophyte flora (mosses, liverworts and hornworts) totalled 173 species, consisting of 131 mosses, 40 liverworts and 2 hornworts. For this study I conducted one month of field studies on the island, during which I collected more than 650 specimens, and also studied collections from the island held in Australian herbaria and other collections available in overseas herbaria. Fourteen moss, 32 liverwort and 1 hornwort species are newly reported from Lord Howe Island, including one liverwort new to science. A further 2 moss and 2 liverwort varieties are also new to the island. Twenty-eight moss and 11 liverwort species are discounted from the island’s flora, as well as 3 moss varieties and 1 liverwort variety. As a result, the known bryophyte flora now totals 178 species, consisting of 117 moss species (122 taxa), 58 liverwort species (60 taxa) and 3 hornwort species. These totals exclude 5 moss and 2 liverwort species whose taxonomic status or presence on the island is considered uncertain. One liverwort variety, Heteroscyphus echinellus var. echinellus, is new to Australia. Fourteen bryophyte species and one variety are endemic to the island. Spiridens muelleri, previously thought to be the same as S. vieillardii from New Caledonia, is shown to be a separate species endemic to Lord Howe Island. Chiloscyphus howeanus is also shown to be a legitimate species endemic to the island. Cololejeunea elizabethae is described as a new species, also endemic to the island. Trachyloma wattsii, considered to be endemic to Lord Howe Island, is supported by a molecular analysis as a legitimate species most closely allied to T. planifolium. Confusion about the correct identities of the two Ptychomitrium species on the island is resolved through a revision of the genus for Australia. A previously unrecorded morphological character of Atrichum androgynum is described from a study of Lord Howe Island plants, and a molecular analysis shows that South American plants previously ascribed to A. androgynum do not belong to that species. Hypnodendron vitiense is shown to be paraphyletic, but not as circumscribed by Touw (1971). The Lord Howe Island plants appear to belong to a morphologically cryptic species distinct from H. vitiense s.str, and substantial genetic variation within H. vitiense subsp. australe as currently circumscribed suggests that it might include more than one taxon. Other molecular investigations clarify the relationship between Lord Howe Island populations and mainland Australian populations of a number of moss species. An original and novel investigation of the potential modes of transport of bryophyte propagules to and from the island is made, and a hypothesis is formed about the origins of its bryophyte flora and the biogeographic relationships to the Australian land mass and other western Pacific islands, including New Zealand and New Caledonia. The nearest region of the Australian mainland is shown to be the most likely origin of most of the island’s bryoflora, with the injection of propagules into the high-level jet stream by storms the most likely dispersal mechanism. The presence of numerous otherwise tropical species on the island is probably a result of dispersal by tropical cyclones moving into the Pacific from north-eastern Australia. Migratory birds are shown to be another potential vector for bryophyte dispersal to the island.
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ItemMacro-evolution in brittle stars( 2018)Conspicuous large-scale diversity patterns and the disparity of species-richness across different taxonomic groups have fascinated naturalists for centuries. In recent years, advances in molecular techniques have facilitated the generation of large amounts of genetic data and have permitted the investigation of long-standing macro-evolutionary questions in a phylogenetic framework, even when the fossil record is scant. With the deep-sea being largely unexplored, many questions remain unanswered and processes affecting diversity in the oceans are far less understood than in terrestrial or aquatic ecosystems. Brittle stars have become a great model to study evolutionary processes, as an extensive genomic dataset has been generated. In this thesis, I aimed to identify large-scale diversity patterns in the oceans and to investigate their underlying processes in a phylogenetic framework. I used this extensive dataset, global distributional records, and novel phylogenetic approaches to investigate major processes at global scales. I investigated the dynamics of bathome shifts and the role of the deep-sea in generating diversity. The findings of bathymetric ranges being highly conserved, and shifts being infrequent, served as a baseline for the other chapters where evolutionary processes were investigated within bathomes. I also investigated the effect of the emergence of biogeographic barriers in shaping diversity patterns of tropical, shallow-water brittle stars. The temporally and spatially concordant divergences of clades, concordant across families, evidenced the role of plate tectonics in shaping spatio temporal patterns of diversity. Similarly, the role of geological processes in the evolution of the fauna of southern Australia was investigated. Three major components have been identified for this fauna, which are the result of geological and historical processes. Recent colonisations, either from tropical species colonising higher latitudes or temperate taxa dispersed from other regions in the Southern Ocean, have been identified based on fossil evidence. However, although a Gondwanan component has been suggested, fossils from the late Cretaceous are scarce, limiting our knowledge about the effect of the break-up of Gondwana. Revisiting this question using one of the most complete metazoan phylogenies to date reaffirm the important role of the Antarctic Circumpolar Current (ACC) in shaping diversity patterns in the Southern Hemisphere, but also of the break-up of Gondwana. Lastly, I investigated colonisations of anchihaline environments. Although several marine taxa have cave-adapted lineages, only three brittle stars have been reported to occur in these environments. As, these species belong to different families, they must represent independent colonisation events. I used evidence from multiple loci to perform species delimitation using robust methods, and assessed models of origin of cave fauna in a phylogenetic framework, considering life-history traits, and demographic history for the cave population. The questions addressed in this thesis evidence the power of phylogenomic approaches that in combination with extensive distributional datasets, shed light into macro-evolutionary processes. The results presented herein contribute and advance our knowledge about diversity and evolutionary processes in our oceans, and provide a framework for future research.
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ItemEvolution and ecology of the Australian Heliozelidae (Adeloidea, Lepidoptera)( 2018)The Heliozelidae (Adeloidea: Lepidoptera) are a family of small, primitive day-flying moths with a worldwide distribution. In recent years, potentially hundreds of new species have been collected around Australia, predominantly in the southwest region of Western Australia. Overall, our observations suggested that many Australian species have evolved independently from other groups in the family. In particular, there is one group of Australian species possessing a unique pollen-carrying abdominal cleft that have established a remarkably close association with species of the Rutaceae (Sapindales) plant genus Boronia. In order to understand the evolution of the Australian Heliozelidae, a robust phylogenetic framework of the Heliozelidae family was required. Additionally, examination of the origins and purpose of the unique morphology of pollen-carrying species and the nature of the associations with their Boronia hosts was crucial to understand their ecological role. Thus, in the first part of this thesis (Chapters Two and Three), I focused on resolving the phylogeny of the worldwide Heliozelidae family and placing the Australian species within it. In Chapter Two, I generated a preliminary phylogeny identifying the major Heliozelidae clades and identify Australia as one of the regions with high undescribed diversity. In Chapter Three, I estimated a fully resolved time-calibrated phylogeny of the major heliozelid clades, with an ancestral range estimation tracing the origins of the family to the Australian region around 96 Mya, during the Late Miocene. In the second part of the thesis (Chapters Four and Five), I focused on the group of Western Australian species that has formed a remarkable association with species in the plant genus Boronia. In Chapter Four, I presented a molecular phylogeny of the Boronia pollinator moths and found preliminary evidence of cospeciation between the moths and their Boronia hosts. In Chapter Five, I described the remarkable active pollination behaviour in three different species of Boronia pollinator, and established the obligate pollination relationship between B. megastigma and its heliozelid pollinator. The findings from this thesis suggest that Heliozelidae play an important role in the Australian environment, exemplified through their close pollination association with the predominantly Australia genus Boronia. Thus, further research into this family of small day-flying moths, which has been poorly studied in Australia until now, is required to better understand their significance.