Neighborhood Effects of Herbivore-Induced Plant Resistance Vary Along an Elevational Gradient

Abstract

The activation of plant defense systems in response to herbivory or experimentally applied methyl jasmonate (MeJA) involves the production of chemical defense substances functioning as warning signals to repel herbivores and protect against pathogens. They also serve as signals detectable by undamaged neighboring plants, a phenomenon called plant-plant communication. We studied how altitudinal variation in temperature and timing of snowmelt affected herbivore resistance, growth and reproduction of untreated bilberry (Vaccinium myrtillus L.) 20-500 cm from MeJA-treated ramets. Across 2 years, responses of MeJA-treated and untreated bilberry ramets were recorded twice per season along an elevational gradient in a boreal system. At low and medium altitudes, untreated bilberry showed increased herbivore resistance and reduced growth and reproduction up to 500 cm from MeJA-treated ramets. In the warmer sites at these altitudes, the effects persisted for 2 years for ramets up to 100 cm from the treated ramets. At high altitudes, however, only untreated ramets growing 20-100 cm from the treated ramets showed increased resistance to insect herbivores and reduced reproduction, but these effects did not persist into the second year. Altitudinal variation in climate affected trade-offs between plant defense, growth, and reproduction. Our findings indicate that plant-plant communication is also influenced by the combination of changes in climate and time after induction. Adaptations of plants growing under increasing temperature in high-latitude environments can profoundly impact ecosystem functioning, especially where bilberry, the key plant species in the boreal system, interacts with its herbivores.

The abundance and diversity of fruit flies and their parasitoids change with elevation in guava orchards in a tropical Andean forest of Peru, independent of seasonality

“…For example, lower levels of nutrients available to plants at high elevations could negatively impact fruit fly performance [64,65]. Also, several defensive plant secondary metabolites, such as alkaloids, coumarins, phenolics, and terpenes, usually vary along elevational gradients [65][66][67][68], with a trend toward a decrease in chemical defenses at higher elevations due to reduced selection pressure by herbivores. In addition, elevation is associated with changes in fruit fly physiology (e.g.…”

Adult facilitation becomes competition as juvenile soapberry bugs age

“…Conversely, plant defenses may intensify competitive interactions if herbivory induces increased expression of defensive compounds or structures (Karban & Baldwin, 1997 ; Quintero & Bowers, 2013 ; Van Zandt & Agrawal, 2004 ) or if reduced plant quality increases individual resource demand through compensatory feeding (Simpson & Simpson, 1990 ). These interactions need not occur synchronously in time, as the induction or suppression of plant defenses by herbivores can persist well beyond the moment of feeding (Benevenuto et al., 2020 ; Bouagga et al., 2018 ; Kant et al., 2015 ; Nosko & Embury, 2018 ).…”

Plant-herbivore interactions: experimental demonstration of genetic variability in plant-plant signaling

“…Studies on plant-plant interactions in response to herbivory often used field-based approaches (Fowler and Lawton, 1985; Karban et al, 2000, 2003, 2016; Karban and Baxter, 2001; Pearse et al, 2013; Morrell and Kessler, 2017; Benevenuto et al, 2020). Such an approach was associated with a dependence between the environment of the emitter and of the receiver.…”

“…Receivers of herbivore-induced signals can also produce secondary metabolites, or toxins within leaves (Himanen et al, 2010;Sugimoto et al, 2014) that limit the palatability of receiver plants when herbivores feed on them. Leaf consumption on receiver plants of herbivore-induced signals was mainly measured over long period of time (days, weeks or years) (Rhoades, 1983;Fowler and Lawton, 1985;Agrawal, 2000;Karban et al, 2000Karban et al, , 2003Karban et al, , 2016Morrell and Kessler, 2017;Benevenuto et al, 2020). Recent studies also showed an effect of plant-plant signaling on herbivore fitness component, as their fecundity or their growth (Morrell and Kessler, 2017;Moreira et al, 2018).…”

“…For instance, environmental clines, such as altitudinal gradients, has a strong effect on plant-herbivores interactions mediated by plant-plant signaling (Benevenuto et al, 2020). In their study, Benevenuto and colleagues (2020) showed that simulated attacks of herbivore on bilberry plants reduced leaf consumption on conspecific neighbors at low and mid altitude, but had no effect at high altitude, indicating potential costs of induced defenses in stressful environments. Here, we used a highly cosmopolitan plant, Arabidopsis thaliana , to investigate the potential intraspecific variability of the effect of plant-plant signaling on plant-herbivore between genotypes originating from various environmental conditions.…”