Wednesday, May 28, 2008 - 3:00 PM
440

An experimental test of increased stream temperature on aquatic insect emergence timing and adult size

Judith L. Li1, Sherri L. Johnson2, Janel Banks3, and William Gerth3. (1) Department of Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331, (2) Pacific NW Research Station, US Forest Service, 3200 SW Jefferson Way, Corvallis, OR 97331, (3) Fisheries and Wildlife, Oregon State University, 104 Nash Hall, Corvallis, OR 97331

Stream temperature is a major influence of aquatic insect emergence, affecting maturation rates, body size, and fecundity. In laboratory experiments, we examined the effects of 3 thermal regimes on emergence timing and adult body size of Psychoglypha and Paraleptophebia. We collected larvae from local streams and raised them in laboratory troughs with temperatures of natural first- and third-order streams, including diel temperature fluctuations. A third treatment had temperatures 3°C above the third-order stream. Survival rates were >85 % for Psychoglypha and >35 % for Paraleptophebia. Emergence of Psychoglypha males from the warmest treatment began 23 days before the females from the same treatment or individuals of either sex from the other treatments. Adult Psychoglypha size did not differ among treatments, but overall females were significantly larger than males (p<0.05). Preliminary results for Paraleptophebia indicate that they did not emerge earlier when temperature was elevated and there were no differences in adult sizes among treatments. We plan to continue these experiments with additional taxa; our initial findings suggest that subtle changes in thermal regimes, such as those associated with land management or climate change, may have effects on aquatic insect maturation and adult body size that are species-specific.


Web Page: life history; abiotic drivers for emergence

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