Evol Ecol Res 8: 169-180 (2006)     Full PDF if your library subscribes.

Sex-specific life-history responses to seasonal time constraints in an alpine caddisfly

Lisa N.S. Shama* and Christopher T. Robinson

Department of Limnology, EAWAG/ETHZ, Überlandstrasse 133, 8600 Dübendorf, Switzerland

Author to whom all correspondence should be addressed.
e-mail: lisa.shama@eawag.ch


Hypotheses: (1) Facultative species that occur in permanent and temporary streams can be locally adapted to their stream of origin or exhibit life-history plasticity. (2) Temporary stream populations respond to environmental cues signalling stream drying whereas permanent stream populations do not. (3) Sex-specific selection pressures imposed by seasonal time constraints imply that males prioritize early maturation whereas females maximize body size at maturity.

Organism: Permanent and temporary stream populations of the alpine caddisfly Allogamus uncatus (Trichoptera) in the Val Roseg, Switzerland.

Methods: We used a common garden experiment to test whether males and females from both stream types differed in their life-history response to combined changes in photoperiod (ambient vs. late) and hydroperiod (constant vs. drying).

Results: Caddisflies exhibited life-history plasticity, although responses varied by time constraint cue and sex. Both sexes shortened development time in the late photoperiod treatments, but neither sex showed a stronger developmental response when exposed to both time constraint cues. Males emerged earlier and at a smaller size than females, and permanent stream males responded to stream drying. Females from both populations increased growth rate in the combined stress treatment, but only permanent stream females responded to hydroperiod stress with decreased growth rate and size at emergence. Temporary stream insects did not emerge earlier than permanent stream insects.

Keywords: aquatic insect, hydroperiod, photoperiod, plasticity, protandry, temporary stream, Trichoptera.

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        © 2006 Lisa N.S. Shama. All EER articles are copyrighted by their authors. All authors endorse, permit and license Evolutionary Ecology Ltd. to grant its subscribing institutions/libraries the copying privileges specified below without additional consideration or payment to them or to Evolutionary Ecology, Ltd. These endorsements, in writing, are on file in the office of Evolutionary Ecology, Ltd. Consult authors for permission to use any portion of their work in derivative works, compilations or to distribute their work in any commercial manner.

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