Management perspectives
Our analysis of standing genetic variation across the distribution of jarrah found putative links between potentially adaptive loci and crucial abiotic factors in stress response, which provide a source of adaptation to climate change. The evidence that genetic variants are involved with climate adaptation occurred as either association with specific gene functions or abiotic responses. Our analysis here, and that of the co-dominant species marri, are also consistent with results from recent genomic studies on other eucalypt species in other regions of Australia (Steane et al., 2017; Jordan et al., 2017, 2020), providing evidence of adaptation to climate in natural populations and stressing the role of temperature (particularly TSEAS and TMAX) and precipitation (PWQ) variables. The presence of climate adaptation provides a basis for implementation of assisted gene migration for forest management strategies (Aitken & Bemmels, 2016) and climate adjusted provenance in restoration practices (Prober et al., 2015). As a foundation tree, jarrah is a vital component in the ecosystem and has a significant role in regulating local hydrological systems and carbon storage (CCWA, 2013; Bradshaw, 2015). Additionally, it offers abundant habitats for a wide variety of groups, from vascular flora and lichens to terrestrial vertebrates and birds (Whitford & Williams, 2002; Whitford et al., 2015), as well as unique food sources for fauna, especially birds (Wrigley, 2012; Lee et al., 2013). Since the middle of the 19th century, it has been a major component of timber production from SWWA forests (CCWA, 2013; Davison, 2015). The Forest Management Plan 2014–2023 (CCWA, 2013) for SWWA forests has provision for implementation of assisted gene migration in management strategies for response to climate change. Our findings of standing variation harbouring putative adaptations to climate associated with temperature and precipitation factors provides an evidence base for design and implementation of such strategies. In addition, phenotypic approaches on other eucalypt species have also highlighted the role of local climate in the development of adaptive traits (Costa e Silva et al., 2019; Ahrens et al., 2019b, Ahrens et al., 2021b). Expanding this work to a phenotypic approach in jarrah for identifying patterns of plasticity and adaptation associated with climate would contribute to further understanding the association of genomic and phenotypic diversity across environmental gradients. While it appears that genetic variants associated with similarly functioning genes are adapting to the environment in similar ways, we found that putative adaptations among climate variables are sorted through the landscape in contrasting ways. This makes implementation of assisted gene migration strategies more complex and targeted in particular areas of the distribution. In fact, our findings illustrate that perhaps we could consider germplasm from multiple sources to bolster the adaptability in adaptively depauperate populations and, by design, we would implicitly choose variation from functionally related genes, potentially increasing the diversity, adaptability, and new combinations of genetic variations.