Plants and insects play a far more intricate game than we suspect, says a University of Toronto researcher in the journal Science this month. Likening the game to one of cat and mouse, botany professor Anurag Agrawal suggests that both plants and insects have the inherent ability to adjust their behaviour - going so far as to alter their physiology and chemistry - in reaction to other species.
"On initial inspection you may think that both the caterpillar and the plant are exceedingly static - the plant just sits there and can't run away from the insect while the caterpillar is essentially stuck on that one plant as it feeds," says Agrawal. "There seems to be little flexibility in terms of their interactions. What I'm arguing is that nothing is further from the truth."
Plants respond to insect damage, he says. In fact, plants are so tuned to their predators that they can detect the difference between a caterpillar and a beetle. The moment a butterfly lays an egg or a moth starts eating a leaf, the plant responds by adjusting its growth, look, smell and behaviour by releasing specific chemicals and toxins to defend itself against the particular insect. Insects, in turn, adjust their phenotype - how they look and behave - and their physiological state by adapting the enzymes in their stomach to better digest the plant. This flexible cat-and-mouse strategy resulted from millions of years of co-evolution, Agrawal says.
"Instead of plants evolving maximal levels of defence and insects evolving maximal levels of counter-defence, both organisms have given themselves the latitude to be flexible in years when there's going to be a lot of the other species around. They're able to tailor their behaviour and physiology to the needs of the environment. And they're able to adjust this behaviour over the course of their individual lifetime."
Agrawal's work was funded by the Natural Sciences and Engineering Research Council, the Premier's Research Excellence Award, the Canadian Foundation for Innovation and the University of Toronto botany department.