Population‐wide shifts in herbivore resistance strategies over succession

Abstract

As a strategic cost‐saving alternative to constitutive resistance, induction of resistance against herbivores in plants can be especially beneficial when enemies are scarce or variable in abundance. Although probably describing the two ends of a continuum, constitutive and induced resistance strategies have long been observed to trade off within species. Examining these traits among populations along a successional gradient can help explain how temporally variable environments can maintain genetic variation and how ecosystem processes are affected by shifting plant resistance trait expression over time. Here we leverage large experimental plots that represent a chronosequence of succession up to 15 yr in combination with common garden experiments to examine changes in the selective environment and genetic differences in tall goldenrod’s (Solidago altissima) constitutive and induced resistance. We show that resistance against a specialist herbivore Trirhabda virgata was inducible in the plants originating from midsuccession, which coincides with the largest loads of herbivores. The flavonoid compound content of the leaves varied with successional stage of the population of origin, which is indicative of constitutive differences in secondary metabolite production. Finally, there was a clear trade‐off between constitutive and induced resistance. Our study indicates that selection for resistance traits within a population can be highly variable over time and likely result in genetically determined shifts of resistance strategies over relatively short time periods via genotype sorting.

Evolution and seed dormancy shape plant genotypic structure through a successional cycle

“…S1). In such early successional communities, competition, herbivory, and genotypic turnover typically increase until perennial vegetation suppresses colonizing species (15,(22)(23)(24). In our experiment, after five annual generations and densities upwards of 200 plants/m 2 , in 2012, experimental populations crashed to ∼2 plants/m 2 and then quickly disappeared altogether (Fig.…”

Experimental insect suppression causes loss of induced, but not constitutive, resistance in Solanum carolinense

“…Horsenettle is also obligately outcrossing, so the presence of viable fruits in all of our plots across multiple years suggests at least moderate genetic diversity within the foraging range of the site's dominant buzz pollinators (Kariyat et al 2013). These assertions notwithstanding, we suggest that disentangling the mechanisms of rapid defense shifts in plants following herbivore suppression is a fruitful area for future research, particularly given the growing evidence of the ubiquity of these types of responses across systems (Coverdale et al, 2018;Kalske & Kessler, 2020;Uesugi & Kessler, 2016).…”

“…Inducible defenses further complicate efforts to understand changes in defense traits over time because studies of ecological communities-where defense induction is typically investigated-often assume that the phenotypes of focal species are fixed or, at the very least, that phenotypic evolution is sufficiently slow that it is unlikely to affect the outcome of ecological interactions (Thompson, 1998;Weber et al, 2017). There is now ample evidence to reject this assumption in the context of plant resistance against herbivores (e.g., Agrawal et al, 2012Agrawal et al, , 2018Bode & Kessler, 2012;Coverdale et al, 2018;Kalske & Kessler, 2020;Turley et al, 2013). For plant defenses, it is also clear that the prevalence of different phenotypes can change rapidly in response to shifts in herbivore regime, and that this variation can result from independent shifts across multiple defense traits, trade-offs among traits, and differences in trait plasticity.…”

“…For example, assuming that defenses are both costly to produce and beneficial in the presence of herbivores, spatiotemporal variation in natural selection arising from heterogeneous herbivory should be a major driver of variation in defense (Agrawal et al, 2018). In support of this notion, investigations spanning macroevolutionary (Becerra et al, 2009;Charles-Dominique et al, 2016) and microevolutionary (Bode & Kessler, 2012;Kalske & Kessler, 2020) timescales have repeatedly found tight correspondence between plant investment in resistance traits and the intensity of herbivory. The same is true regarding spatial variation in herbivory across landscapes (Coverdale et al, 2018(Coverdale et al, , 2019.…”

Effect of Grazing Treatments on Phenotypic and Reproductive Plasticity of Kobresia humilis in Alpine Meadows of the Qinghai-Tibet Plateau

“…The biomass of all traits in this experiment indicates that the grazing treatments only promoted the redistribution of material in K. humilis but did not reverse the distribution pattern of material in each trait. Bradshaw (2006) noted that changes in plant morphology are one of the driving forces of community succession (Kalske and Kessler, 2020), and are a mechanism to increase plant adaptation under high levels of disturbance. This is a result of long-time interaction between plants and domestic animals (Li et al, 2021).…”