Date of this Version
DeBoer, J. A., J. J. Fontaine, C. J. Chizinski, and K. L. Pope. 2015. Masked expression of life-history traits in a highly variable environment. Great Plains Research 25:25-38.
Differing life-history strategies may act as a constraint on reproductive expression that ultimately limits the ability of individual species to respond to changes in the magnitude or frequency of environmental variation, and potentially underlies the variation oft en inherent in phenotypic and evolved responses to anthropogenic change. Alternatively, if there are environmental cues that predict reproductive potential, differential expression of life-history strategies may represent differences in the adaptive capacity to optimize current reproductive value given variation in environmental conditions. We compared several aspects of walleye Sander vitreus spawning ecology at two reservoirs that diff er in environmental variability (i.e., annual water-level fluctuation) to identify the capacity of phenotypic expression and the corresponding association with age. Despite signifi cant differences in female body and liver masses between reservoirs that differ in environmental variability, we found no diff erence in reproductive investment measured by egg size and fecundity. Walleye in a highly variable environment appear to exhibit reproductive traits more typical of a short- lived life-history strategy, which may be resultant from the interaction of environmental and anthropogenic pressures. Th is finding emphasizes the need to identify the degree to which life- history expression represents physiological constraints versus ecological optimization, particularly as anthropogenic change continues to alter environmental conditions.
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