Caddisflies growth and size along an elevation/temperature gradient

Abstract

Temperature influences biological systems ranging from biochemical reactions to ecosystem processes. Some traits such as growth, development, and body size are related to temperature. Here, we ask the question whether the size of trichopteran changes along a ~ 1200 elevation gradient, as a predictor of temperature. Additionally, we measured in laboratory growth rates of the caddisfly Schizopelex festiva under three temperature regimes. Specimens of Hydropsyche ambigua, Hydropsyche siltalai, and Rhyacophila adjuncta were smaller at low than at high elevations. For each increase in 2 °C (downwards 400 m in the mountain), there was a 6.6 ± 2.3% decrease in size. Under laboratory conditions, specimens of Schizopelex festiva grew faster at 20 °C (34.7 ± 6.5 µg mg−1 day−1) than at 15 and 10 °C (18.9 ± 4.1 and 16.7 ± 2.3 µg mg−1 day−1, respectively). We conclude that caddisflies are sensitive to temperature along elevation gradients; we predict that ongoing global warming may affect aquatic insects body size and other related parameters such as survival and fitness.