Plant traits that predict resistance to herbivores

Abstract

Summary1. Although secondary metabolites are recognized as fundamental to the defence of plants against insect and mammalian herbivores, their relative importance compared to other potential defensive plant traits (e.g. physical resistance, gross morphology, life-history, primary chemistry and physiology) are not well understood. 2. We conducted a meta-analysis to answer the question: What types of genetically variable plant traits most strongly predict resistance against herbivores? We performed a comprehensive literature search and obtained 499 separate measurements of the strength of covariation (measured as genetic correlations) between plant traits and herbivore susceptibility -these were extracted from 72 studies involving 19 plant families. 3. Surprisingly, we found no overall association between the concentrations of secondary metabolites and herbivore susceptibility -plant traits other than secondary metabolites most strongly predicted herbivore susceptibility. Specifically, genetic variation in life-history traits (e.g. flowering time, growth rate) consistently exhibited the strongest genetic correlations with susceptibility. Genetic variation in gross morphological traits (e.g. no. branches, plant size) and physical resistance traits (e.g. latex, trichomes) were also frequently correlated with variation in herbivore susceptibility, but these relationships depended on attributes of the herbivores (e.g. feeding guild) and plants (e.g. longevity). 4. These results call into question the conventional wisdom that secondary metabolites are the most important anti-herbivore defence of plants. We propose the hypothesis that herbivores select most strongly on genetic variation in life-history, morphological and physical resistance traits, but the greater pleiotropic effects of genes controlling these traits impose strong constraints on their evolution. Meanwhile, secondary metabolites could have evolved to be important defensive mechanisms not because they have the largest effect on herbivores, but because the constraints on their evolution are the weakest.

Influence of plant resistance traits in selectiveness and species strength in a tropical plant‐herbivore network

“…Our fi ndings show the relevance of considering more than one foliar attribute to predict the interaction patterns in a plant-herbivore network, as has been documented when predicting herbivore damage ( Agrawal and Fishbein, 2006 ;Carmona et al, 2011 ;Loranger et al, 2012 ;Schuldt et al, 2012 ). Our results suggest that leaf mechanical traits (toughness and trichome density) were better predictors of plant species strength and herbivore selectiveness than the percentage of oxidized phenolics.…”

“…Chemical and physical resistance traits of plants aff ect the foraging behavior and performance of herbivores, infl uencing the magnitude of their interaction with diff erent host plants ( Coley and Barone, 1996 ;Pilson, 2000 ;Poelman et al, 2008 ;Fatouros et al, 2014 ). For example, leaf toughness is a physical barrier ( Lucas et al, 2000 ;Read and Stokes, 2006 ;Peeters, 2007 ) that is highly correlated with herbivore damage ( Coley, 1983 ) and offers effective resistance against herbivores ( Summerville and Crist, 2003 ;Hanley et al, 2007 ;Clissold et al, 2009 ;Carmona et al, 2011 ). Trichomes constrain the movement of herbivores and aff ect larval consumption and survival ( Zalucki et al, 2002 ;Handley et al, 2005 ;Tian et al, 2012 ) and oft en exudate toxic chemicals ( Lin et al, 1987 ).…”

Genetic and Environmental Factors Behind Foliar Chemistry of the Mature Mountain Birch

“…Phenology also is tied to herbivore performance: the main herbivores are able to eat off a tree only during certain stages of the phenology. If the phenology is genetically determined, trees sampled at the same time may have different chemical profiles simply because they differ in phenology (Carmona et al, 2011). Studying individual traits separately may not lead to ecologically relevant results.…”

“…These changes in chemistry indirectly affect herbivory (Bryant et al, 1983). In addition to chemical variability as such, the rate at which the phenology proceeds during the spring and summer may also have a genetic basis, and this too may play an important part in herbivory defense (Carmona et al, 2011).…”

Effect of Disease Resistance on Secondary Herbivores: Aphid Abundance on Hybrid and Non-hybrid Coffee Varieties in the Chagga Homegardens

“…A study of cocoa plants in Ghana showed that syrphid abundance correlates positively with aphid abundance [10]. Conspecific plants experience differences in herbivore susceptibility due to variations in phenological, morphological and chemical defense traits [11]. It is therefore possible that the altered morphology and heightened defense response of introduced hybrid coffee varieties could affect herbivore feeding behavior.…”