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

Abstract

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.

Host plant phenology, insect outbreaks and herbivore communities – The importance of timing

“…Similarly, we also detected an effect of host genotype on aphid incidence, where one particular genotype (“G4” in Figure ) tended to show a higher probability of infestation than did other genotypes. This pattern matches the results of a previous study using the same oaks, where the very same genotype (“G4” in Figure ) tended to show a higher abundance of aphids in an environment with elevated temperatures (Faticov, Ekholm, Roslin, & Tack, ). In terms of overall effects, indirect effects of oak genotype (mediated via phenology) were more pronounced than direct effects of genotype on the insect herbivore community, implying that direct effects of genotype were of minor importance.…”

“…in Figure 4) tended to show a higher abundance of aphids in an environment with elevated temperatures (Faticov, Ekholm, Roslin, & Tack, 2019). In terms of overall effects, indirect effects of oak genotype (mediated via phenology) were more pronounced than direct effects of genotype on the insect herbivore community, implying that direct effects of genotype were of minor importance.…”

The forgotten season: the impact of autumn phenology on a specialist insect herbivore community on oak

“…As an important distinction between the inference of Connor et al (1994) and the current study, we note that Connor et al (1994) were explicitly concerned with how year-to-year variation affects the abundance of C. hamadryadella. In our study, we focus on spatial variation in autumn phenology, and explicitly assume that differences in phenology observed during a single year offer an indication of long-term differences in relative phenology -as supported by persistent changes among oak trees and genotypes within oak stands (Faticov et al, 2019;Crawley & Akhteruzzaman, 1988). Thus, the effects examined by Connor et al (1994) reflect phenotypic plasticity alone (as being related to temporal variation within the same oak individuals), whereas in the setting of our study, changes in oak phenology with climate change are likely to reflect both phenotypic plasticity and evolutionary change within the oak population.…”

“…Trees show high intraspecific variation in spring and autumn phenology (Crawley & Akhteruzzaman, 1988;Vitasse et al, 2009;Cole & Sheldon, 2017). Such differences show a substantial genetic component (Faticov et al, 2019), and persist over time (Crawley & Akhteruzzaman, 1988). The timing of budburst has proved to be important in determining the herbivore damage on host plants, but also in affecting the occurrence and abundance of herbivorous insects (Crawley & Akhteruzzaman, 1988;Mopper & Simberloff, 1995;Sinclair et al, 2015;Heimonen et al, 2017).…”

Degradation of Visible Autumn Icons and Conservation Opportunities: Trends in Deciduous Forest Loss in the Contiguous US

“…The synergy of these stressors is even less understood. For example, stressed trees likely undergo earlier senescence and, depending on the stress, more complete coloration, but climate warming can delay timing (Schaberg et al 2003; Faticov et al 2019). Recent studies suggest increased vulnerability of temperate forests to disease and invasion during periods of stress, but impacts to autumn aesthetics are unknown.…”