Effects of biotic and abiotic factors on the distribution and abundance of larval two-lined salamanders (Eurycea bislineata) across spatial scales.

We sampled eight streams in the White Mountain National Forest, New Hampshire, throughout their elevational reach for larval salamanders and predatory fish to examine the effects of abiotic factors and predation on the distribution and abundance of larval salamanders. Eurycea bislineata (two-lined salamander) and Salvelinus fontinalis (brook trout) abundance varied among and within streams. Eurycea bislineata showed a negative association with S. fontinalis across spatial scales (micro-scale, among quadrats; meso-scale, among pool/riffle pairs; macro-scale, among streams). At the smallest scale, the average density of larval E. bislineata was greatest in microhabitats with relatively high boulder cover and low sand and bare rock cover only in the presence of S. fontinalis; no such relationship was observed in the absence of S. fontinalis. In a mesocosm experiment, larval salamander survival was higher in enclosures containing cobbles than enclosures containing a gravel mix, illustrating the advantage of coarse substrates with interstitial spaces that are inaccessible to predatory fish. At the meso-scale, E. bislineata larvae were less abundant in stream sections with S. fontinalis than those without. Among streams, those with many S. fontinalis had fewer E. bislineata. Of the abiotic parameters measured, water temperature and pH were positively related to E. bislineata presence, and elevation, water temperature, pH, canopy cover, and gradient were positively related to E. bislineata abundance. Larval Plethodontid salamanders can reach high densities and appear to have strong interactions with stream biota, thus their functional role in stream communities deserves further attention.