Do insect pests perform better on highly defended plants? Costs and benefits of induced detoxification defences in the aphid Sitobion avenae

• Published in: Journal of evolutionary biology 2010-11, Vol.23 (11), p.2474-2483
• Main Authors: CASTAÑEDA, L.E, FIGUEROA, C.C, NESPOLO, R.F
• Format: Article
• Language: English
• Subjects: Adaptation, Biological - genetics; Adaptation, Biological - physiology; Adaptations; Analysis of Variance; Animals; Aphididae; Aphids - enzymology; Aphids - genetics; Aphids - physiology; Basal Metabolism; Chile; Colonization; Cytochrome P-450 Enzyme System - metabolism; Cytochrome P450 monooxygenase; Detoxification; detoxification enzymes; Environment; Enzyme Induction - drug effects; Enzyme Induction - genetics; Enzymes; esterase; Evolutionary biology; Feeding; Fitness; fitness cost; Gene Frequency; Genetic diversity; Genetic Variation; Genotype & phenotype; Genotypes; Glutathione transferase; Glutathione Transferase - metabolism; Grain; Host plants; Hydroxamic acid; Hydroxamic Acids - pharmacology; Insects; insect‐plant interaction; Metabolic rate; Microsatellite Repeats - genetics; Pests; Phenotype; phenotypic plasticity; plant chemical defences; Plasticity; Population genetics; Reproduction; Sitobion avenae; standard metabolic rate; Stress; trade‐offs; Triticum - metabolism; Triticum - parasitology; Triticum aestivum
• ISSN: 1010-061X; 1420-9101
• DOI: 10.1111/j.1420-9101.2010.02112.x

Induced defences are a typical case of phenotypic plasticity, involving benefits for ‘plastic' phenotypes under environments with variable degree of stress. Defence induction, in turn, could be energetically expensive incurring costs on growth and reproduction. In this study, we investigated the genetic variation and induction of detoxification enzymes mediated by wheat chemical defences (hydroxamic acids; Hx), and their metabolic and fitness costs using five multilocus genotypes of the grain aphid (Sitobion avenae). Cytochrome P450 monooxygenases and glutathione S‐transferases activities were seen to increase with Hx levels, whereas esterases activity and standard metabolic rate increased in wheat hosts with low Hx levels. Additionally, the intrinsic rate of increase (a fitness proxy) increased in highly defended hosts. However, we did not find significant genetic variation or genotype-host interaction for any studied trait. Therefore, aphids feeding on host plants with elevated chemical defences appeared to reduce their detoxification costs and to increase their reproductive performance, which we interpret as a novel adaptation to defended plants. In brief, this study supports the notion that aphids perform better on highly defended host plants, probably related to the selective pressures during the colonization of New World agroecosystems, characterized by highly defended host plants.