ECOLOGY OF ECOTONES: INTERACTIONS BETWEEN SALAMANDERS ON A COMPLEX ENVIRONMENTAL GRADIENT

Abstract

We investigated factors that define boundaries between assemblages of streamside and terrestrial plethodontid salamanders by manipulating the moisture gradient in the ecotone between headwater streams and upland forests in the Allegheny Mountains of Virginia. Two experiments tested the hypothesis that microhabitat distributions of species change in response to competitors whose distributions are controlled by variation across the landscape at a larger scale. In the first experiment we created replicated seeps (continuously moist patches) 3 m and 15 m from streams. Desmognathus fuscus, a streamside species, began to increase in density at streamside seeps and to colonize distant seeps within 1.5 mo of their construction. Plethodon cinereus, a small terrestrial species, initially responded favorably to distant seeps but was displaced as seeps were colonized by streamside species. The D. fuscus colonists remained on distant plots with seeps 22 mo after water to seeps was turned off and the habitat had return...