The causes of natural selection

Abstract

The authors discuss the necessary and sufficient conditions for identifying the cause of natural selection on a phenotypic trait. They reexamine the observational methods recently proposed for measuring selection in natural populations and illustrate why the multivariate analysis of selection is insufficient for identifying the causal agents of selection. The observational approach of multivariate selection analysis can be complemented by experimental manipulations of the phenotypic distribution and the environment to identify not only how selection is operating on the phenotypic distribution but also why it operates in the observed manner. Instead of viewing the environment as a source of unwanted variation that obscures the relationship between phenotype and fitness, fitness is viewed as arising from the interaction of the phenotype with the environment. The biotic and abiotic environment is the context that gives rise to the relationship between phenotype and fitness (selection). The experimental study of the association between selection gradients and environmental characteristics is necessary to identify the agents of natural selection. -from Authors