Plant defence to sequential attack is adapted to prevalent herbivores

Plants have evolved plastic defence strategies to deal with the uncertainty of when, by which species and in which order attack by herbivores will take place(1-3). However, the responses to current herbivore attack may come with a cost of compromising resistance to other, later arriving herbivores. Due to antagonistic cross-talk between physiological regulation of plant resistance to phloem-feeding and leaf-chewing herbivores(4-8), the feeding guild of the initial herbivore is considered to be the primary factor determining whether resistance to subsequent attack is compromised. We show that, by investigating 90 pairwise insect-herbivore interactions among ten different herbivore species, resistance of the annual plant Brassica nigra to a later arriving herbivore species is not explained by feeding guild of the initial attacker. Instead, the prevalence of herbivore species that arrive on induced plants as approximated by three years of season-long insect community assessments in the field explained cross-resistance. Plants maintained resistance to prevalent herbivores in common patterns of herbivore arrival and compromises in resistance especially occurred for rare patterns of herbivore attack. We conclude that plants tailor induced defence strategies to deal with common patterns of sequential herbivore attack and anticipate arrival of the most prevalent herbivores. Plants have developed defences against herbivores, but with multiple threats at different times, those defences may be compromised. This experiment finds that plants adapt over time to anticipate prevalent herbivores and common patterns of attack.

Automated summary

Plants have developed diverse defence strategies to deal with attacks from herbivores, adjusting their responses based on common patterns of herbivore arrival to anticipate the most prevalent herbivores.