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Curtin University (2017)

Evolutionary Adaptations to Climate Change in Australian Flora

D’Agui, Haylee Marie

Titre : Evolutionary Adaptations to Climate Change in Australian Flora

Auteur : D’Agui, Haylee Marie

Université de soutenance : Curtin University

Grade : Doctor of Philosophy (PhD) 2017

Résumé
Climate changes have been impacting ecosystems worldwide, causing shifts in the habitats suitable for plant species and threatening their continuing persistence. Mediterranean-type Ecosystems contain extraordinarily high levels of plant diversity and endemism, yet are vulnerable to climate and environmental changes. Southwest Western Australia is recognised as a global biodiversity hotspot, though has been experiencing decreased rainfall and increased drought over the past 40 years, causing great concerns for the long-term survival of its extraordinary plant diversity. Plants may respond to changes in climate by migrating to new habitats, persisting in their current habitat, or by adapting to changes through evolution. In this thesis, I investigated the potential of Southwest Western Australian plants to rapidly evolve to tolerate changes in climate, particularly decreased rainfall and increased temperature. I first assessed the floristic composition of a nature reserve in speciose kwongan heathland following four decades of decreased rainfall and increased temperature through comparison of a present day vegetation survey to historic surveys. In Chapter 3, I further investigated the potential of seed banks to mitigate the effects of decreased rainfall through comparison of the growth of seedlings descended from parents established in years of either average or below-average rainfall when subjected to drought and control treatments. In Chapter 4, I explored the potential of Banksia hookeriana (Proteaceae) to accumulate adaptive genetic variation in order to resist the effects of a drying climate through the assessment of the fitness of seedlings established from seed produced pre- and post- drought to determine whether post-drought seed displayed increased drought tolerance. Finally, in Chapter 5, I investigated whether adaptive genetic diversity in B. attenuata was affected by rainfall and temperature gradients, or altered fire regime through genomic scanning and environmental association analysis on plants distributed across its range to determine candidate genes associated with these environmental variables. Overall, results from my study suggest that the flora of Southwest Western Australia has been able to tolerate the changes in climate that have occurred so far, and that there may be potential for tolerance of further changes in climate. However changes in fire regime in the region may have a detrimental effect on the ability of some species to adapt and survive.

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