Abstract
Two native, stream-associated amphibians are found in coastal streams of the west coast of North America, the tailed frog and the coastal giant salamander, and each interacts with stream insects in contrasting ways. For tailed frogs, their tadpoles are the primary life stage found in steep streams and they consume biofilm from rock surfaces, which can have trophic and non-trophic effects on stream insects. By virtue of their size the tadpoles are relatively insensitive to stream insect larvae, and tadpoles are capable of depleting biofilm levels directly (exploitative competition), and may also “bulldoze” insect larvae from the surfaces of stones (interference competition). Coastal giant salamander larvae, and sometimes adults, are found in small streams where they prey primarily on stream insects, as well as other small prey. This predator-prey interaction with stream insects does not appear to result in differences in the stream invertebrate community between streams with and without salamander larvae. These two examples illustrate the potential for trophic and non-trophic interactions between stream-associated amphibians and stream insects, and also highlights the need for further research in these systems.
Highlights
Stream foodwebs around the globe are typically dominated numerically and in terms of biomass by invertebrates, the larval stages of aquatic insects
Predation interactions between amphibians and insects can go in both directions, with insects preying upon amphibian larvae [11,12], and amphibians, salamanders, feeding on aquatic insects [8,13,14]
These two species are the tailed frog, Ascaphus truei Stejneger (Anura: Leiopelmatidae), a species that grazes on rock biofilms as tadpoles, and Dicamptodon tenebrosus Baird and Girard (Caudata: Dicamptodontidae), the coastal giant salamander, which is predaceous as larvae and adults
Summary
Stream foodwebs around the globe are typically dominated numerically and in terms of biomass by invertebrates, the larval stages of aquatic insects. We use two stream-dwelling amphibian species from the Pacific Northwest of North America to illustrate the possible interactions with aquatic insects, and their potential for population- and community-level consequences These two species are the tailed frog, Ascaphus truei Stejneger (Anura: Leiopelmatidae), a species that grazes on rock biofilms as tadpoles, and Dicamptodon tenebrosus Baird and Girard (Caudata: Dicamptodontidae), the coastal giant salamander, which is predaceous as larvae and adults. We first introduce these species, and review the evidence for their indirect and direct interactions (competition and predation) with aquatic insects. Due to their large size and generalist feeding behavior, aquatic D. tenebrosus act as top predators in many headwater streams
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