Facilitation and inhibition: changes in plant nitrogen and secondary metabolites mediate interactions between above-ground and below-ground herbivores

Abstract

To date, it remains unclear how herbivore-induced changes in plant primary and secondary metabolites impact above-ground and below-ground herbivore interactions. Here, we report effects of above-ground (adult) and belowground (larval) feeding by Bikasha collaris on nitrogen and secondary chemicals in shoots and roots of Triadica sebifera to explain reciprocal aboveground and below-ground insect interactions. Plants increased root tannins with below-ground herbivory, but above-ground herbivory prevented this increase and larval survival doubled. Above-ground herbivory elevated root nitrogen, probably contributing to increased larval survival. However, plants increased foliar tannins with above-ground herbivory and belowground herbivory amplified this increase, and adult survival decreased. As either foliar or root tannins increased, foliar flavonoids decreased, suggesting a trade-off between these chemicals. Together, these results show that plant chemicals mediate contrasting effects of conspecific larval and adult insects, whereas insects may take advantage of plant responses to facilitate their offspring performance, which may influence population dynamics.

Plant-Mediated Systemic Interactions Between Pathogens, Parasitic Nematodes, and Herbivores Above- and Belowground

“…Both root herbivores and nematodes can be the facilitators, and both pathogens and herbivores can be the beneficiaries. Conversely, AG herbivores can facilitate BG phytophages by suppressing the BG induction of root-produced secondary metabolites (61). These studies indicate that facilitation between phytophages from either the same or different kingdoms can occur both within and across compartments.…”

“…Larval feeding induces root tannins. However, when adults are feeding on the plant as well, they prevent induction of root tannins, resulting in increased larval survival (61). Interestingly, this intraspecific facilitation is asymmetric; larval feeding amplifies the induction of leaf tannins in response to adult feeding.…”

Plant water stress and previous herbivore damage affect insect performance

“…Changes in abiotic conditions, such as soil nutrients or other environmental stressors, can affect short-term changes in plant nutrition and expression of resistance traits (Bazzaz et al, 1987;Donaldson et al, 2006;Hakes & Cronin, 2011). Herbivore damage can also induce changes in plant traits, such as plant nutrition (Huang et al, 2013) and chemical or physical resistance, which usually, but not always, reduces the performance of subsequent herbivores feeding on damaged plants (Agrawal, 1998;Karban et al, 1997). Although the degree to which abiotic factors and herbivore damage individually contribute to levels of plant resistance and Correspondence: Philip G. Hahn, Division of Biological Sciences, University of Montana,32 Campus Dr.,HS 104,Missoula,MT 59812, herbivore performance is well documented, less is known about the combined effects of abiotic factors and previous herbivory on the subsequent performance of larval insects.…”

Adult facilitation becomes competition as juvenile soapberry bugs age

“…Plant defenses are important determinants of herbivore fitness that mediate indirect interactions between herbivores. In plant-feeding insects, host plant defenses are a common moderator of both competition (Karban and Baldwin 1997) and facilitation (Soler et al 2012; Huang et al 2013; Glas et al 2014). Competition is the most common net outcome of multiple individual herbivores sharing a plant (Kaplan and Denno 2007), primarily via the induction of plant defenses (Karban and Baldwin 1997).…”