Bears Indirectly Affect Plant Fitness

If you haven’t seen it yet, there’s a really cool paper in Ecology Letters about the indirect effects of bears on ecological communities (Grinath et al. 2015). Did you know that bears will eat ants? Well, they will! Especially during periods when they are food limited. And when bears disturb ant nests, the ants stop tending the leaf and tree hoppers (=herbivorous insects) that they farm for honeydew. Without ants patrolling nearby, tree hoppers experience higher predation pressures from other arthropod predators, like lady beetles and spiders. And when the densities of herbivorous insects decline, plant fitness increases. So, by eating ants, bears can increase plant fitness! Nuts!

HungryBears

I glossed over some of the details of this story, such as variation in the effects of bears across years. To get all of the details and to see some cool structural equation modeling, go check out the paper!

Reference:

Grinath, J.B., B.D. Inouye, and N. Underwood. 2015. Bears benefit plants via a cascade with both antagonistic and mutualistic interactions. Ecology Letters 18(2): 164-173.

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