Divergent host plant utilization by adults and offspring is related to intra‐plant variation in chemical defences

Abstract

Adult and juvenile herbivores of the same species can use divergent feeding strategies, and thus may inhabit and consume different parts of the plant. Because the expression of chemical defences often differs between host plant tissues, this variation may result in disparate performance outcomes for adult and juvenile conspecifics that feed on distinct dietary substrates. The goal of this study was to evaluate how host range may differ between adults and juveniles in a generalist herbivore. We addressed the impacts of among‐ and within‐plant defence variation using the wood‐feeding Asian longhorned beetle (Anoplophora glabripennis) and three host plants having a range of putative resistance. Impacts of host plants on adult and offspring performance were assessed using a series of controlled bioassays. We evaluated adult‐feeding and egg‐laying behaviours in choice and no‐choice experiments using the different hosts, and subsequent offspring establishment. We then evaluated host plant chemical composition related to nutrition and defence. Different plants had strong impacts on adult performance, but these patterns did not extend to effects on offspring. Females were capable of developing eggs when provided Acer rubrum, but not Populus deltoides or Populus tomentosa. Females that produced eggs by feeding on A. rubrum, however, deposited eggs into all three plant species. Larvae hatched and consumed tissues in all three hosts. The differences between adult and juvenile utilization of Populus spp. were reflected in markedly higher salicinoid phenolic concentrations in bark (>2% dw), while wood had trace quantities. Our results demonstrate that plant resistance mechanisms can differentially act upon adult and juvenile life stages of a polyphagous herbivore when there is differential expression of chemical defences among plant tissue types. Anoplophora glabripennis has been a globally successful invader due in part to its broad host range, and our results suggest a mechanism that permits the beetle to exploit marginally resistant plants. This study has implications for how host range differs between insect feeding stages, which is particularly important for invasive, polyphagous species encountering novel food sources.

Plant chemicals affect trade-offs between adult preference and larval performance of the rice water weevil, Lissorhoptrus oryzophilus

“…In addition, in this study, avonoid and oxalate in roots appear to have less effects on RWW larvae than the effect of those chemicals in leaves on adults. Due to their limited mobility and food exploration ability, larvae likely have a stronger ability to detoxify plant defences than adults (Mason et al 2019). We also acknowledge that some other chemicals such as lipids which were not measured in this study might affect RWW growth in this study.…”

Correlations among morphological and biochemical traits in high‐cannabidiol hemp (Cannabis sativa L.)

“…Ecological theory predicts ontogenetic and tissue‐specific variation in the concentration of plant secondary metabolites, primarily in the context of herbivore resistance (Barton & Boege, 2017 ; McKey, 1974 ; Meldau et al, 2012 ; Pavia et al, 2002 ; Schuman & Baldwin, 2016 ; van Dam, 2009 ). There are many examples of ecologically relevant intra‐organismal variation in secondary metabolite concentration across diverse taxa, including Gossypium (Anderson & Agrell, 2005 ), Brassica (Gutbrodt et al, 2012 ), Acer (Mason et al, 2019 ), Populus (Mason et al, 2019 ), Caulerpa (Meyer & Paul, 1992 ), Dictyota (Cronin & Hay, 1996 ), and Oceanapia (Schupp et al, 1999 ). The well‐studied cases of biochemically‐mediated plant resistance to herbivores provide insight into the evolutionary drivers responsible for heritable intra‐plant variation in secondary metabolites.…”

Factors driving the within‐plant patterns of resource exploitation in a herbivore

“…availability, accessibility, nutritional quality and defence compounds) or to the forager (e.g. physiological status, interactions with antagonists) can influence foraging decisions (Bee et al, 2011; Ho et al, 2019; Kraus et al, 2019; Mason et al, 2019; Vanderplanck et al, 2020; Woodard et al, 2019). However, we currently lack studies embracing several of these factors to assess their relative effect on foraging behaviours.…”

“…However, availability, accessibility as well as defence compounds and nutritional quality of food sources can also vary within species and even within a given plant. Indeed, plant quality can depend on the organ, its degree of maturity or a particular location in this organ (Brown et al, 2003; Kouki & Manetas, 2002; Mason et al, 2019; Rodrigues et al, 2008). Therefore, individual plants represent a mosaic of patches that may be differentially profitable for herbivores, in the same way as different plant species do (Galdino et al, 2015).…”