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.