A scientific basis for assisted gene migration under climate change

Abstract

Climate change is altering global temperature and rainfall regimes. Yearly measures of temperature have seen a warming trend into the 21st Century compared to the long-term average. Species' vulnerability is determined by their exposure to climate change and sensitivity to changes in temperature and precipitation. The capability of species and populations to persist through climate change is dependent on their adaptive capacity acquired through standing adaptive genomic variation and phenotypic plasticity. In this thesis, we aim to quantify the adaptive capacity of red gum Eucalyptus taxa through the analysis of genomic adaptation to climate and physiological tolerance under water-limited conditions. In Chapter 2, we focus on two closely related species with widespread distributions, E. blakelyi and E. tereticornis subsp. tereticornis, that traverse climatic gradients across eastern Australia. In Chapter 3, we aimed to determine the adaptive genomic variation of threatened narrowly-distributed (restricted) red gum taxa, E. glaucina, E. parramattensis, and E. tereticornis subsp. mediana and related widespread species E. blakelyi and E. tereticornis subsp. tereticornis. In Chapter 4, we performed a controlled water-limitation experiment to estimate the physiological tolerance of widespread (E. blakelyi, E. tereticornis), and restricted ((E. glaucina and E. parramattensis) red gum eucalypts to drought. Overall, across these data chapters, we find that the red gum eucalypts have the apparent capacity to persist through climate change through standing adaptive genomic variation and physiological tolerance under water-limited conditions. Some populations may be genomically vulnerable, however, there appears to be putatively adaptive genomic variation within the species as a hole. We determined that this adaptive capacity is not ubiquitous across species, nor among populations. Eucalyptus parramattensis appears to exhibit the lowest genomic capacity to adapt to new climates due to the lower genomic variation observed, and despite varied climate ranges, marginal populations of the widespread species may still be vulnerable to climate change. Widespread and restricted taxa may still have the phenotypic plasticity to persist through drought-like conditions. We provide fundamental insights into the genetic and physiological mechanisms for drought response in eucalypts. The outcomes provide the scientific evidence to support land managers and policy-makers to develop active management strategies, including assisted gene migration of climate-ready (through the detection of putatively adaptive genomic variants) individuals to build the resilience and long-term persistence of natural populations under climate change.

Date of Award	2021
Original language	English