Plants adapt their defenses to the local pest community

Populations of the same plant species produce specific defenses that are effective against the predominant local pest community. Variation in the local pest community can therefore maintain genetic variation in plants across large geographical scales. Ecologists from the University of Zurich used controlled experiments coupled with observations on natural plant populations and their pests to demonstrate how genetic variation in plant defenses is maintained. The results could be used to develop customized seeds that are more resistant to the local pest community.

Populations of the same plant species produce specific defenses that are effective against the predominant local pest community. Variation in the local pest community can therefore maintain genetic variation in plants across large geographical scales. Ecologists from the University of Zurich used controlled experiments coupled with observations on natural plant populations and their pests to demonstrate how genetic variation in plant defenses is maintained. The results could be used to develop customized seeds that are more resistant to the local pest community.

Herbivorous insects, such as aphids, damage plants and can substantially reduce yields in agricultural settings; however, they can play a major role in maintaining genetic diversity. Ecologists Tobias Züst and Lindsay Turnbull from the University of Zurich together with colleagues from California and Great Britain demonstrated the importance of variation in herbivore communities using the model plant, Arabidopsis thaliana, also known as wall cress. According to Züst, the work is one of the first experimental confirmations of a forty-year-old theory that herbivorous insects exert strong selective pressure on their host plants. Moreover, plants were quick to abandon defense mechanisms when pests were absent, confirming the high costs of these defenses.

Like many other plants, Arabidopsis thaliana, or wall cress, defends itself against pests with a sophisticated chemical arsenal. The pests, however, continually evolve mechanisms to tolerate or metabolize particular chemical components. This means that depending on the abundance of different pest species, different compounds will provide optimal protection, and thus the plant needs to produce a carefully tailored cocktail that will be effective against the most likely attackers. The researchers’ first step was to study the distribution of different chemical defenses in natural populations of Arabidopsis thaliana across Europe and compare it to the geographic distribution of two important pest species: the cabbage and the mustard aphid.