Bio21 - Theses
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ItemClimate adaptation in Eucalyptus microcarpa (Grey Box) and implications for conservation( 2017)Restoration is an important component of conservation management, especially in highly modified landscapes. In the face of rapid environmental change, the mere presence of vegetation doesn’t necessarily equate to the long term sustainability of populations. Rather, there is a need to consider evolutionary potential in conservation planning, including restoration. This thesis investigates two key components of evolutionary potential pertinent to restoration – namely genetic diversity and climate adaptation – in an important restoration tree species in south-eastern Australia, Eucalyptus microcarpa. This thesis aims to understand how genetic diversity and local adaptation are distributed across the range of E. microcarpa and how this knowledge may help inform seed sourcing and enhance resilience of restoration plantings under climate change. To begin, I use a landscape genomic approach to explore genomic diversity in E. microcarpa and how diversity in small habitat remnants and revegetation (restored) sites compare to large remnants. This work found that small, habitat remnants and revegetation sites largely, but not completely captured patterns of genomic diversity across the landscape. Whilst overall genomic diversity was similar between site types, patterns of diversity across the genome varied between site types. These results suggest important genomic differences between site types that may influence future adaptive potential of revegetation sites and small habitat remnants. I then investigated adaptation to climate in E. microcarpa using multiple approaches. Firstly, using a landscape genomic approach, I found evidence of genomic climate adaptation in E. microcarpa. These results suggest climate adaptation to be a genome-wide phenomenon, involving many genes and genomic regions. Exploration of genomic changes that may be required to match projected climate change suggest adaptation to be via shifts in allele frequency from standing variation. In addition to suggesting a number of climate variables associated with adaptation in E. microcarpa, these results highlight the importance of genetic diversity and standing variation for maintaining adaptive potential. Utilising existing genetic resources for this species, I found evidence of heritable, genetic variation in growth and leaf traits of E. microcarpa growing in a provenance trial. Furthermore, significant trait variation between provenances and associations with climate variables suggest climate as a driver of adaptive differences. Finally, I combined the independent genomic and phenotypic analyses to provide stronger support for climate adaptation in E. microcarpa, including links between genomic variants and adaptive traits. Associations between traits and single nucleotide polymorphisms (SNPs) using putatively adaptive SNPs genotyped in provenance trial trees validated genomic results, suggesting some trait variation could be explained by these SNPs. Furthermore, links between all three sources of variation relevant to local adaptation – genotype, phenotype and climate – corroborated findings of the two independent analyses. This approach therefore provides greater support for adaptation to climate in E. microcarpa. Together these analyses address the current genetic state of restoration in E. microcarpa as well as the structure of genetic diversity and climate adaptation across its distribution. These results suggest adaptive differences within E. microcarpa that could be utilised to enhance evolutionary potential within restoration plantings.