This case study of adaptation in Arabidopsis thaliana shows that natural selection on early life stages can be intense and can influence the evolution of subsequent traits. Two mechanisms contribute to this influence: pleiotropy across developmental stages and developmental niche construction. Examples are given of pleiotropy of environmentally cued development across life stages, and potential ways that pleiotropy can be relieved are discussed. In addition, this case study demonstrates how the timing of prior developmental transitions determines the seasonal environment experienced subsequently, and that such developmental niche construction alters phenotypic expression of subsequent traits, the expression of genetic variation of those traits, and natural selection on those traits and alleles associated with them. As such, developmental niche construction modifies pleiotropic relationships across the life cycle in ways that influence the dynamics of adaptation. Understanding the genetic basis of life-cycle variation therefore requires consideration of environmental effects on pleiotropy.