Plant defence to sequential attack is adapted to prevalent herbivores

Plants have evolved plastic defence strategies to deal with uncertainty of
when, by which species and in which order attack by herbivores will take
place. 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, 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 pair-wise 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.