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.

Investigating Ex Situ Competitive Interactions in a Novel Fish Community with Implications for the Introduction of Sunfish (Lepomis spp.) in Headwater Streams

“…Mesocosms were 60 3 120 3 60 cm fiberglass tanks outfitted with a recirculating pump system. Each stream mesocosm drained into its own sump, creating independent replicates and base flows and temperatures similar to local streams and prior experiments (13.7±0.18C; 40.5 L/min; Ennen et al, 2016; Cecala et al, 2020). Mesocosms were set up to replicate a small stream pool environment.…”

Elevated temperatures alter competitive outcomes and body condition in southern Appalachian salamanders

“…We conducted our experiment in 16 independent stream mesocosms at the Tennessee Aquarium Animal Care Facility (Ennen et al, 2016). Each stream mesocosm was a recirculating system that consisted of a trial tank (1.20 9 0.60 9 0.53 m) that drained into a plastic sump with a pump that returned water to the trial tank.…”

“…We added 10 crickets (average length 6.4 mm) to each mesocosm weekly for the length of the experiment that lasted 6 weeks (42 days). Previous work suggested this length of time was sufficient to evaluate treatment effects within the mesocosms (Ennen, Davenport & Alford, 2016). At the end of the experiment, all individuals were removed from the mesocosms, identified, measured and weighed to assess outcomes of competition.…”

“…Each stream mesocosm was a recirculating system that consisted of a trial tank (1.20 9 0.60 9 0.53 m) that drained into a plastic sump with a pump that returned water to the trial tank. Water circulated at a rate of 0.6 L s À1 common to native streams and used in other mesocosm experiments (Resetarits, 1991;Lowe, Likens & Cosentino, 2006;Ennen et al, 2016). Water depth was maintained using a standpipe set to 10 cm.…”