Variation in the trophic basis of production and energy flow associated with emergence of larval salamander assemblages from forest ponds

1. Larval amphibians are a dominant consumer in many freshwater systems, yet limited data on energy transfers between aquatic food resources and larvae and between metamorphosed larvae and adjacent habitats preclude an accurate assessment of their roles as links between aquatic and terrestrial food webs. 2. During 2003-04, we derived prey-specific assimilation efficiencies, analysed stomach contents, and intensively sampled ambystomatid salamander assemblages in four ponds to quantify the trophic basis of larval production. Using estimates of the contribution of each prey taxon to larval production, we constructed quantitative food webs and assessed variation in pathways of energy flow associated with emergences. 3. Overall, metamorphosed salamanders exported 3-8% of total prey production, required to account for total salamander production, to adjacent forest. Aquatic insects, zooplankton and amphibian prey were most important to energy flow associated with emergence; amounts of larval production attributed to each of these prey types shifted during development and varied among salamander taxa. 4. The majority of variation in the trophic basis of production among species was attributed to copepods (Cyclopidae) and three families of aquatic insects (Chironomidae, Chaoboridae and Culicidae). Dominant prey types contributing to the production of metamorphosed salamanders varied among ponds, representing different pathways for energy transfers between aquatic resources and forest habitats. These findings further our understanding of the ecological roles of amphibians and thus the consequences of amphibian declines and extinctions.