Evol Ecol Res 5: 213-228 (2003) Full PDF if your library subscribes.
Effects of diet-induced resource polymorphism on performance in arctic charr (Salvelinus alpinus)
Jens Andersson*
Department of Ecology and Environmental Science, Umeå University, S-901 87 Umeå, Sweden
e-mail: jens.andersson@eg.umu.seABSTRACT
Resource polymorphism is found in many taxa and its presence can be a result of both genetic factors and phenotypic plasticity. The aim of this study was to estimate the effect of diet-induced resource polymorphism on individual performance in Arctic char (Salvelinus alpinus). I reared 90 young-of-the-year individuals separately on one of three different diets: a pure zooplankton diet, a pure chironomid diet and a mixture of zooplankton and chironomids. Attack rate and swimming speed were estimated for 10 individuals from each treatment group at the start and the end of the experiment. Morphologies were measured for all 90 individuals at the end of the experiment. I found effects of the treatments on both morphology and performance, and morphology and performance variables correlated at the individual level, suggesting that the morphological changes were adaptive. The zooplankton feeders had the highest attack rate and swimming speed when foraging on zooplankton, followed by the mixed-diet feeders and the chironomid feeders. In contrast, there were no differences in attack rate between treatment groups when foraging on chironomids, although the zooplankton feeders had a higher swimming speed regardless of type of prey. The results suggest that diet itself is not enough to induce different specialists and that other factors, such as population dynamics or predation risk, may act as substrates for the development of resource polymorphism in Arctic charr.
Keywords: competition, geometric morphometrics, performance, phenotypic plasticity, resource polymorphism, Salvelinus alpinus, trade-off.
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