Abstract:
Natural ecosystems are under pressure from increasing abiotic and biotic stressors,
including climate change and novel pathogens, which are putting species at risk of
local extinction, and altering community structure, composition and function. Here,
we aim to assess adaptive variation in growth and fungal disease resistance within a
foundation tree, Corymbia calophylla to determine local adaptation, trait heritability
and genetic constraints in adapting to future environments. Two experimental planting
sites were established in regions of contrasting rainfall with seed families from 18
populations capturing a wide range of climate origins (~4,000 individuals at each site).
Every individual was measured in 2015 and 2016 for growth (height, basal diameter)
and disease resistance to a recently introduced leaf blight pathogen (Quambalaria
pitereka). Narrow‐sense heritability was estimated along with trait covariation. Trait
variation was regressed against climate‐of‐origin, and multivariate models were used
to develop predictive maps of growth and disease resistance. Growth and blight resistance
traits differed significantly among populations, and these differences were
consistent between experimental sites and sampling years. Growth and blight resistance
were heritable, and comparisons between trait differentiation (QST) and genetic
differentiation (FST) revealed that population differences in height and blight resistance
traits are due to divergent natural selection. Traits were significantly correlated
with climate‐of‐origin, with cool and wet populations showing the highest levels of
growth and blight resistance. These results provide evidence that plants have adaptive
growth strategies and pathogen defence strategies. Indeed, the presence of
standing genetic variation and trait heritability of growth and blight resistance provide
capacity to respond to novel, external pressures. The integration of genetic variation
into adaptive management strategies, such as assisted gene migration and seed
sourcing, may be used to provide greater resilience for natural ecosystems to both
biotic and abiotic stressors.
