Evidence for asymmetric competition among headwater stream vertebrates

Abstract

The importance of competition among stream salamanders and other stream vertebrates in headwater systems is understudied. We conducted a replicated artificial stream experiment to evaluate competitive interactions among three common vertebrates. In this experiment, we measured change in body condition of salamanders in the black-bellied dusky complex (Desmognathus quadramaculatus/folkertsi) in the presence of two different fish species, Common Creek Chub (Semotilus atromaculatus) and Coosa Darter (Etheostoma coosae). There was no statistically significant change in body condition between the control and darter present treatments. However, salamander body condition was significantly reduced in the presence of the creek chubs suggesting an asymmetric competitive interaction between those two species. While predation is often cited as a potential mechanism limiting the distribution of stream species, the role of interspecific competition may be just as vital. Overall, our results highlight that competition, and not solely predation, may explain why some stream salamanders are restricted to headwater reaches.