Such instances have not been documented before

May 12, 2010 11:00 GMT  ·  By
A wolf spider crawls on the leaves of the carnivorous sundew, with which it competes for food
   A wolf spider crawls on the leaves of the carnivorous sundew, with which it competes for food

It's no secret that one of the main selection mechanisms of evolution is competition. Within the same species, or between related species, competition is what drives the survival of the fittest, and the main source of potential mates for animals looking to produce offspring. Emerging from skirmishes unscathed is an indicator of fitness, and prospective mates are drawn to the animal that managed such a feat. But competition was always thought to be contained within at least the same kingdoms. A new study shows that this is false altogether, ScienceNow reports.

Animals and plants are two distinct kingdoms. They live independently off each other, and the only interactions they have is when herbivorous animals eat plants, when creatures rest in the shade of trees, or in their branches, and when organic matter from decomposing animals feeds the roots of weeds and so on. But never in the history of science have experts identified an instance when a plant and an animal competed directly for the same food source. It's true, lions fight hyenas and weeds fight crops, but who's ever heard of a sundew plant competing with an insect-eating wolf spider?

Still, this is the case in the damp bogs of southern Florida, where sundews (Drosera capillaris) fight the wolf spider (Sosippus floridanus). The differences between the two organisms are considerable. The carnivorous plant secretes a sticky substance on its leaves, which traps flies, ants, crickets, and springtails, among other insects. The spider species targets the exact same food source, but it generally uses a thick and dense web to get the job done. With their curiosity peaked by the fact that both species lived close to the ground, University of South Florida in Tampa researchers, led by ecologist Jason Rohr, set out to learn if this overlap led to competition.

Results did not fail to show. In an incredible twist of events, the team learned that spiders weaving their webs next to the plants tended to make them larger, as if to show that they can catch more insects. “In web building, it seems the spiders make sensible decisions regarding the level of competition,” Rohr explains in a paper appearing in the May 12 issue of the esteemed scientific journal Proceedings of the Royal Society B. The group also found that, when faced with assiduous competition from spiders, the plants produced less seeds and leaves, on account of being resource-deprived. “It’s very possible that it’s a widespread phenomenon, but we’d need to test it,” Rohr concludes.