Landscape structure and population size effects on genetic pattern and process in Banksia ilicifolia R.Br.: consequences for conservation and ecological restoration

[Truncated abstract] Habitat fragmentation is an issue of conservation concern around the world. An understanding of how fragmentation affects populations on a landscape and local scale will underpin better conservation and ecological restoration outcomes. Habitat fragmentation reduces population size, can reduce connectivity among remnants within a matrix that is altered from the original, and potentially impacts the demographics and genetics of the species affected. A landscape genetic approach can reveal historical and contemporary genetic processes to inform better management choices for conservation and restoration. In this thesis, I take this approach to understand landscape scale genetic diversity and to assess how urbanization affects the important ecosystem function of pollen dispersal in Banksia ilicifolia R.Br. (Proteaceae). I also quantify population size effects on fitness parameters for B. ilicifolia seedlings, and how they respond to environmental stress. The current 700 km range-wide spatial genetic structure of B. ilicifolia was assessed and the impact of historical climatic changes on these genetic patterns inferred. This information provides an insight into how the species may respond to future climate change. Microsatellite markers were developed for B. ilicifolia, and the levels and structuring of genetic variation within and among populations assessed by Mantel tests, principal components analysis and Bayesian clustering. Two broad regional scale genetic clusters were identified. Further analysis of the spatial structure of the allele frequencies strongly suggested a secondary contact zone between these the two regions, following greater separation during the last glacial maximum. This is the first time a secondary contact zone has been demonstrated for a southwest Australian plant species, and shows an impact of past climate change on species distributions in the region. Current climate change may be impacting the distribution of B. ilicifolia in a similar way, and this needs to be considered for conservation management. Understanding how changes in population size and habitat fragmentation affect gene flow at a local scale is important for conservation, as a decrease in pollen input from outside the population as well as disruption to pollen dispersal within the population can lead to elevated inbreeding, a reduction in genetic diversity, and ultimately impact population viability...