RESEARCH: Tougher tree leaves don’t always offer better protection from insects, says new Concordia research

A new study by Concordia researchers has found that leaf toughness doesn’t always stop insects from taking a bite.

In a study published in the Canadian Journal of Forest Research, Biology PhD candidate Mahsa Hakimara and professor Emma Despland explore how the physical traits of leaves such as thickness, toughness and hairiness affect insect feeding.

The researchers looked at two closely related trees: the sugar maple — whose leaf adorns the Canadian flag — and the black maple, a rare and protected species. Both trees are common in Quebec’s forests, but black maple is distinguished by its slightly tougher and hairier leaves.

The team collected data from two forested sites in Quebec over three years, looking at saplings in natural and urban environments. They tracked insect damage on leaves, studied the types of insects feeding on the trees, and ran lab tests to see if caterpillars preferred one tree over the other.

The results were surprising. Though black maple leaves are tougher and have more surface hairs (called trichomes) — thought to hamper insects’ ability to chew, pierce or digest — the researchers found similar levels of insect damage to both tree types.

Caterpillars did not avoid black maple leaves, and they survived just as well when eating them.

This suggests that shared ancestry or other factors, such as chemical defenses, may play a more important role in shaping insect feeding patterns.

The study was funded by Natural Sciences and Engineering Research Council of Canada Discovery Grant (NSERC DG), the Kenauk Institute and SERG-International.

Read the cited paper: “Do physical leaf traits predict insect herbivory? Testing bottom-up pressures in two closely related maple trees in a temperate forest in Quebec”

For more information contact media.relations@concordia.ca