Leaf pseudo-variegation: Definition, common types, and probably the defended models for real defensive leaf variegation mimicking them?

•Leaf variegation was proposed and shown to defend plants from herbivory.•We define variegation induced by external biological agents as pseudo-variegation.•Pseudo-variegation reduces plant food quality for herbivores.•We propose that pseudo-variegation may defend plants from herbivory.•We propose that pseudo-variegation is a defended model for defensive variegation.

Leaf variegation, the outcome of various genetic, developmental and physiological factors, is a well-known phenomenon proposed and even shown experimentally to defend plants from herbivory. A visually similar phenomenon that we define as pseudo-variegation is induced in plants by various external biological agents. We propose that pseudo-variegation may defend leaves and other plant organs (and also some of the organisms that induce them) from herbivory by several visual and chemical mechanisms: camouflage, aposematism and by indicating via olfactory cues/signals that the plants are damaged or occupied by herbivores or pathogens. From an evolutionary point of view, because of the common reduced quality as food and in many cases even toxicity for herbivores of leaves expressing pseudo-variegation, as well as because of competition with pathogens and herbivores that arrived earlier, or because of cannibalistic or predatory herbivores, such leaves were probably the defended models that were later mimicked by plants with mutations that caused various variegated phenotypes. Pseudo-variegation types induced by various pathogens and herbivores that actually defend plants from herbivory should be considered the extended phenotypes of both these plants and of the inducers that in this way defend their plant habitat.