Adaptive variants are independently sorted
Across the species geographic distribution, climatic heterogeneity
explains significant genomic variation. In particular,
TSEAS and PWQ showed strong associations
between environments and gene pools. The patterns of genomic turnover
associated with the studied climatic variables are aligned with the
climatic gradients of the region (Figure 5). These associations are
indicative of the multidimensional patterns of adaptation resulting in
orthogonal intraspecific selection among SNPs (White & Butlin, 2021).
Here, we define dimensionality as the interaction between orthogonal
climate variables to independently describe each habitat. Our
dimensionality is driven by climate, and the independent sorting of
putatively adaptive variants is indicative of this complex pattern. It
has been modelled that local adaptation increases with dimensionality
(MacPherson et al. 2015), and it likely leads to dimensionality of
phenotypic traits (Kirkpatrick and Meyer 2004; McGuigan et al. 2005).
Indeed, there is evidence of intraspecific variation among growth and
morphological traits (e.g., height and diameter at breast height)
locally adapted in jarrah, associated to climatic factors (O’Brien et
al., 2007, 2010; Koch & Samsa, 2007).
In some ways, increased dimensionality is ubiquitous with increased
habitat heterogeneity, and habitat heterogeneity has been shown to drive
signatures of adaptation to temperature and precipitation in tree
species (Shryock et al. 2020; von Takach et al., 2021; Walters et al.,
2021). While these studies did not explore dimensionality explicitly,
their results nevertheless show that tree species are able to
independently adapt to multiple types of environments. While such
patterns of differential adaptation makes management of the species more
complex and nuanced in the future, our results provide a level of
understanding that will allow for targeted responses to changing
climatic conditions in different areas.