The ecology and evolution of plant-pollinator interactions in Australian Typhonium (Araceae)
AuthorSayers, Thomas Daniel John
AffiliationSchool of Ecosystem and Forest Sciences
Document TypePhD thesis
Access StatusThis item is embargoed and will be available on 2021-09-19.
© 2019 Thomas Daniel John Sayers
Pollination is one of the most important interactions in nature, with the vast majority of flowering plants reliant upon biotic vectors for out-crossing and reproduction. Despite this, the pollination systems of most plants are unknown, limiting our understanding of the evolutionary processes that gave rise to these interactions, dependency on specific pollinators for plant reproduction, and the resilience of interactions in the context of environmental change. The species-rich family Araceae is used worldwide as a model to investigate the ecology and evolution of plant-pollinator interactions, yet detailed studies of pollination in the majority of genera remain scarce. One such sizeable genus is Typhonium Schott, the most diverse genus of Araceae in Australia. Using field studies and a range of analyses (morphological, chemical, molecular), this thesis aimed to investigate the diversity, ecology, and evolution of Typhonium plant-pollinator interactions in Australia. This thesis is divided into four research chapters. Chapter 2 identified significant intra and interspecific variation in floral traits and pollinating insects between allopatric populations of the only species with a broad geographic range, Typhonium brownii, and its geographically restricted sister species T. eliosurum. Both mimic dung, but they are functionally specialised to deceive saprophagous beetle or fly pollinators, respectively. Interspecific trait divergence provided insight into the pollinator-mediated selection of floral traits and the importance of morphological filters. Significant intraspecific variation in T. brownii thermogenesis, anthesis rhythms and scent indicates the occurrence of a T. brownii species complex, comprised of more taxa than currently recognised. The function of floral scent for pollinator attraction was confirmed in field bioassays and is discussed in the context of adaptation to the pre-existing biases of pollinators. Chapter 3 investigated pollination systems of tropical T. angustilobum and T. wilbertii, from north Queensland. T. angustilobum and T. wilbertii were similarly identified as brood-site mimics, share similar thermogenic and anthesis rhythms, but are functionally specialised to beetle and fly pollination, respectively, associated with distinct floral scents and morphological filters. Molecular analyses provide the first evidence of heating via the alternative oxidase (AOX) in Typhonium. Chapter 4 combined pollination data on 14 Typhonium species from across their geographic range to explore trends in plant-pollinator interactions. It presents further evidence for functional specialisation to pollination by saprophagous beetle and fly families in a genus characterised by rewardless brood-site mimicry, floral traps and a high frequency of floral thermogenesis. Differences in pollinator type and climatic region were not related to anthesis rhythms or thermogenic properties. Despite significant scent divergence, some broad differences in scent with pollinator type were identified. Given the prevalence of Staphylinidae-flower interactions in Australian Typhonium, Chapter 5 systematically analysed the worldwide extent of rove beetle floral interactions and pollination. At least 108 staphylinid-plant species interactions were identified across 27 seed plant families, the first assessment of the diverse and complex relationships between staphylinids and plants which were previously overlooked. As concluded in Chapter 6, this thesis develops Typhonium as a new model system to investigate the ecology and evolution of brood-site mimicry, an underappreciated yet widespread form of floral mimicry.
Keywordspollination; Araceae; Typhonium; floral mimicry; thermogenesis; floral scent; floral morphology; floral traits; Staphylinidae
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