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EVOLUTION OF A PLASTIC QUANTITATIVE TRAIT IN AN AGE‐STRUCTURED POPULATION IN A FLUCTUATING ENVIRONMENT
Author(s) -
Engen Steinar,
Lande Russell,
Sæther BerntErik
Publication year - 2011
Publication title -
evolution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.84
H-Index - 199
eISSN - 1558-5646
pISSN - 0014-3820
DOI - 10.1111/j.1558-5646.2011.01342.x
Subject(s) - biology , fecundity , trait , reproductive value , selection (genetic algorithm) , population , character (mathematics) , statistics , weighting , natural selection , evolutionary biology , econometrics , mathematics , demography , genetics , offspring , pregnancy , medicine , geometry , radiology , artificial intelligence , sociology , computer science , programming language
We analyze weak fluctuating selection on a quantitative character in an age‐structured population not subject to density regulation. We assume that early in the first year of life before selection, during a critical state of development, environments exert a plastic effect on the phenotype, which remains constant throughout the life of an individual. Age‐specific selection on the character affects survival and fecundity, which have intermediate optima subject to temporal environmental fluctuations with directional selection in some age classes as special cases. Weighting individuals by their reproductive value, as suggested by Fisher, we show that the expected response per year in the weighted mean character has the same form as for models with no age structure. Environmental stochasticity generates stochastic fluctuations in the weighted mean character following a first‐order autoregressive model with a temporally autocorrelated noise term and stationary variance depending on the amount of phenotypic plasticity. The parameters of the process are simple weighted averages of parameters used to describe age‐specific survival and fecundity. The “age‐specific selective weights” are related to the stable distribution of reproductive values among age classes. This allows partitioning of the change in the weighted mean character into age‐specific components.