Herbivory in a changing climate—Effects of plant genotype and experimentally induced variation in plant phenology on two summer‐active lepidopteran herbivores and one fungal pathogen

Abstract

With climate change, spring warming tends to advance plant leaf‐out. While the timing of leaf‐out has been shown to affect the quality of leaves for herbivores in spring, it is unclear whether such effects extend to herbivores active in summer. In this study, we first examined how spring and autumn phenology of seven Quercus robur genotypes responded to elevated temperatures in spring. We then tested whether the performance of two summer‐active insect herbivores (Orthosia gothica and Polia nebulosa) and infection by a pathogen (Erysiphe alphitoides) were influenced by plant phenology, traits associated with genotype or the interaction between these two. Warm spring temperatures advanced both bud development and leaf senescence in Q. robur. Plants of different genotype differed in terms of both spring and autumn phenology. Plant phenology did not influence the performance of two insect herbivores and a pathogen, while traits associated with oak genotype had an effect on herbivore performance. Weight gain for O. gothica and ingestion for P. nebulosa differed by a factor of 4.38 and 2.23 among genotypes, respectively. Herbivore species active in summer were influenced by traits associated with plant genotype but not by phenology. This suggest that plant attackers active in summer may prove tolerant to shifts in host plant phenology—a pattern contrasting with previously documented effects on plant attackers active in spring and autumn.

Effects of leaf herbivory and autumn seasonality on plant secondary metabolites: A meta‐analysis

“…Chemical ecology temperatures are causing winter to become shorter in some geographical regions, with frost occurring later in the season (Loe et al, 2021;Sparks & Menzel, 2002;Williams et al, 2015) and leaf herbivory extending into early autumn (Gallinat et al, 2015;Loe et al, 2021;Zani et al, 2020), such as with caterpillars, leaf miners, and gall wasps (Ekholm et al, 2019(Ekholm et al, , 2022. For example, Lemoine et al (2014) found that the feeding rates of 11 herbivoreplant pairs (e.g., Atteva aurea and Ailanthus altissima, Danaus plexippus and Asclepias syriaca, among others) increased with warming temperatures.…”

“…Such interactions are relevant because insects can be active during the non‐growing season (i.e., autumn and winter), such some leafhoppers (Stinson & Brown, 1983 ), sawflies (Kause et al., 2001 ), and larvae of leaf‐mining moths (Connor et al., 1994 ), which re‐appear with a second generation during late summer and/or consume leaves until senescence occurs in mid to late autumn (Connor et al., 1994 ). Furthermore, warming temperatures are causing winter to become shorter in some geographical regions, with frost occurring later in the season (Loe et al., 2021 ; Sparks & Menzel, 2002 ; Williams et al., 2015 ) and leaf herbivory extending into early autumn (Gallinat et al., 2015 ; Loe et al., 2021 ; Zani et al., 2020 ), such as with caterpillars, leaf miners, and gall wasps (Ekholm et al., 2019 , 2022 ). For example, Lemoine et al.…”