Climate and host genotype jointly shape tree phenology, disease levels and insect attacks

One of the best known ecological consequences of climate change is the
advancement of spring phenology. Yet, we lack insights into how changes in
climate interact with intraspecific genetic variation in shaping spring
and autumn phenology, and how such changes in phenology will translate
into seasonal dynamics of tree-associated organisms. To elucidate the
impact of warming and tree genotype on spring and autumn phenology, as
well as the consequences for the population dynamics of a fungal pathogen
(Erysiphe alphitoides) and plant-feeding insect (Tuberculatus annulatus),
we conducted an active field heating experiment using grafts of five oak
genotypes (Quercus robur). We found that experimental warming generally
advanced oak bud burst in spring and delayed leaf senescence in autumn,
while additional variation was explained by tree genotype and
warming-by-genotype interactions. Warming or tree genotype did not affect
disease levels at the beginning of the season, but shaped both disease
levels and aphid density during the latter part of the season. Overall,
our findings demonstrate that elevated temperature and genetic variation
affect spring and autumn phenology, as well as the seasonal dynamics of
higher trophic levels. Such effects may be either direct (i.e. temperature
affecting tree phenology and attack independently) or indirect (as due to
climate-induced changes in plant traits or the synchrony between trees and
their attackers). To achieve a predictive understanding of the ecological
responses and potential evolutionary changes of natural food webs in
response to climate warming, we should merge the frameworks of global
warming and community genetics.