Harvard University researchers Jim Karagatzides and Aaron Ellison discovered such plants generally appear in environments that have few nutrients.
"Carnivory allows these plants to capture nutrients 'on the wing'," said Ellison.
"But if it's so good to be a carnivorous plant in these kinds of environments, why aren't there more carnivorous plants? Knowing how much it 'costs' a carnivorous plant to make a trap is a key piece of information needed to understand why there aren't more carnivorous plants."
Elllison and Karagatzides measured both costs and benefits for traps, leaves, roots and rhizomes of 15 different carnivorous plant species. They measured the construction cost of carbon needed to create plant structures and compared it to the payback time -- the amount of time it takes to photosynthesize the carbon used in its construction -- to determine how beneficial a trap might be to a plant.
They said they discovered the average cost to create a trap was actually significantly lower than the cost to create a leaf.
"The most interesting result is that carnivorous traps are 'cheap' to make -- at least compared with leaves," said Ellison.
The study is detailed in the American Journal of Botany.
Copyright 2009 by United Press International.