How wallflowers evolved a complementary pair of plant defenses

Flower of the Rhaetian wallflower (Erysimum rhaeticum) under attack by a caterpillar. Image: Tobias Züst - A new study led by Tobias Züst from the Institute of Plant Sciences of the University of Bern shows that a pair of complementary chemical defenses evolved independently in wallflowers, shaped by co-evolution with local insects. A pair of chemicals used by wallflowers and their kin to ward off predators have evolved to complement each other, with one targeting generalist herbivores and the other targeting specialized herbivores that have become resistant to the generalist defense. Plants are engaged in an ongoing arms race with the creatures that eat them. They evolve defenses to deter plant eaters, while their herbivores evolve counter-defenses. The new study, published today in eLife, reveals details of the evolutionary chemical arms race in the wallflower genus Erysimum, a group of flowering plants in the mustard family Brassicaceae. The defense lines of the wallflowers.