Abstract
As an increasing number of ecosystems face departures from long standing environmental conditions under climate change, our understanding of the capacity of species to adapt will become important for directing conservation and management of biodiversity. Insights into the potential for genetic adaptation might be gained by assessing genomic signatures of adaptation to historic or prevailing environmental conditions. The river red gum (Eucalyptus camaldulensis Dehnh.) is a widespread Australian eucalypt inhabiting riverine and floodplain habitats which spans strong environmental gradients. We investigated the effects of adaptation to environment on population level genetic diversity of E. camaldulensis, examining SNP variation in candidate gene loci sampled across 20 climatically diverse populations approximating the species natural distribution. Genetic differentiation among populations was high (FST = 17%), exceeding previous estimates based on neutral markers. Complementary statistical approaches identified 6 SNP loci in four genes (COMT, Dehydrin, ERECTA and PIP2) which, after accounting for demographic effects, exhibited higher than expected levels of genetic differentiation among populations and whose allelic variation was associated with local environment. While this study employs but a small proportion of available diversity in the eucalyptus genome, it draws our attention to the potential for application of wide spread eucalypt species to test adaptive hypotheses.
Highlights
Trees are foundation species in many terrestrial ecosystems and changes to local environment associated with natural and anthropogenic climate change are projected to impact, or are already impacting, the health of forest tree populations and the ecosystems they service worldwide [1,2,3,4,5]
In this study we examined genetic diversity and divergence of 59 single nucleotide polymorphisms (SNPs) markers sampled from twelve candidate gene loci in 20 populations of E. camaldulensis distributed across the species natural range
SNP selection and genotyping Using single nucleotide polymorphisms (SNPs) we examined the variability of twelve genes in trees sampled across the natural range of E. camaldulensis
Summary
Trees are foundation species in many terrestrial ecosystems and changes to local environment associated with natural and anthropogenic climate change are projected to impact, or are already impacting, the health of forest tree populations and the ecosystems they service worldwide [1,2,3,4,5]. Plant populations adapt to environmental change through a combination of mechanisms including reversible changes to their physiological or morphological phenotypes independent of genotype (e.g. phenotypic plasticity); adaptation of phenotypes via changes in allelic composition as a result of selection (e.g. genetic adaptation); and migration to more suitable environments (e.g. seed or pollen dispersal). In some forest trees these responses will be insufficient to track rapid climate redistribution [5,13], depending on the rate and magnitide of enviroimnetal change, physiological tolerances, life-history strategies (e.g. generation time), dispersal abilities, population dynamics, interspecific competition and levels of genetic diversity [6,13,14]
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