GENETIC CONSTRAINTS TO LIFE-HISTORY EVOLUTION IN THE PITCHER-PLANT MOSQUITO, WYEOMYIA SMITHII.

Life-history theory relies heavily on the hypothesis that genetic tradeoffs among the components of fitness constrain their independent evolution and joint maximization. Herein we show that selection on preadult development time in the pitcher-plant mosquito, Wyeomyia smithii, leads to a correlated response in cohort mean generation time but no correlated response in survivorship, fecundity, or cohort replacement rate. Lines selected for fast development achieve a higher capacity for increase (rc ) than lines selected for slow development, independently of larval density. These results imply that tradeoffs due to underlying antagonistic pleiotropy affecting growth, development, survivorship, and reproduction are not necessary constraints to life-history evolution. Previous work with W. smithii has shown a positive genetic correlation between development time and a general, genetically coordinated diapause syndrome. We propose that the observed nontradeoffs among the components of rc may be subsumed into an even more fundamental tradeoff between performance during the summer generations and synchronization of development and reproduction with the changing seasons. Consequently, critical tests of genetic tradeoffs as a constraint to the independent evolution or simultaneous optimization of fitness components may need to consider the seasonal context. © 1996 The Society for the Study of Evolution.