Evolution Under Interspecific Competition: Field Experiments on Terrestrial Salamanders

Hairston, Nelson

Two species of terrestrial salamanders have different distributional relationships on different mountain ranges in the southern Appalachians. Individuals of P. jordani were relocated into prepared plots where both they and the original inhabitants (P. glutinosus) were monitored for five years. In the Great Smoky Mountains, where the high-altitude Plethodon jordani and the low-altitude P glutinosus overlap vertically by only 70-120 m, removal experiments showed them to be in intense competition. In the Balsam Mountains, where the altitudinal overlap is at least 1,220 m, removal experiments revealed the existence of competition, but at a less intense level than in the Smokies. Transferring P jordani between the areas of intense and weak competition showed that both species have evolved in ways that decrease competition in the Balsam Mountains, because neither has an appreciable effect on the opposite species from the Great Smoky Mountains. This result is as expected from recently elaborated evolutionary-ecological theory. In the Smokies, by contrast, both species have evolved competitive mechanisms sufficiently potent to keep them almost completely separated altitudinally Both have a stronger effect on the opposite species from the Balsams than the local Balsam populations have on each other. This result is not well explained by current theories of evolutionary ecology.

Evolution Under Interspecific Competition: Field Experiments on Terrestrial Salamanders

Series