ambience Rainforest, Iquitos, Peru
In the Amazon, there’s an incredible diversity of plants and insects that feed on those plants. Well, different plants have developed different strategies for defending themselves against insects, and those strategies are based on the kind of soil the plant grows in. I’m Jim Metzner, and this is the Pulse of the Planet.
“Imagine a world without insects that eat plants. The plants could, perhaps, grow on all kinds of different soil types. The ones that are growing on the low nutrient soils are going to grow slightly slower, and the ones growing on high nutrient soils, like clays, are going to go grow slightly faster.”
Paul Fine is an Assistant Professor in Ecology and Evolutionary Biology at the University of Michigan. He tells us there are two basic kinds of soil in the Amazon – – red clay which is high in nutrients, and white sand which is much less fertile.
“When you add insects to the equation, it magnifies the differences between soil types because plants trying to replace the tissues lost to insects are going to have a much more difficult time of doing that on low nutrient soils like white sand. Thatâ€™s going to create what we call a selection pressure for plant defenses, meaning that a plant that has a plant defense that is defending it against insects will get an advantage.”
The main defense for plants that grow in fertile red clay soil is to grow faster than insects can devour them, while plants that grow in low nutrient white sand have evolved to produce chemical and other defenses against insects.
“White sand plants are famous for having lots of resins and latexes, lots of tannins, which are found in plants all over the world, and thicker, tougher leaves, all of which are thought to help protect them against insect enemies.”
Strangely enough, the insects that prey upon these plants have helped maintain the diversity of plant species in the rainforest. We’ll hear how in future programs. Pulse of the Planet is presented by the National Science Foundation. I’m Jim Metzner.