The evolution of reproductive isolation in closely adjacent plant populations through differential flowering time

Abstract

A model is proposed for the non-selective displacement of flowering time in closely adjacent plant populations. Numerical results obtained on a single locus model as well as a polygenic simulation model demonstrate that an environmental difference may trigger genetic divergence of flowering time. This divergence results because there is non-random migration with respect to flowering time, which has effects like those demonstrated by Thoday and Gibson (1970) in an experiment in which selective migration alone gave genetic divergence between habitats with respect to sternopleural bristle number in Drosophila melanogaster. In view of the results it is suggested that the evolution of reproductive isolation may sometimes start through a selectively neutral process, which can secondarily enhance the adaptation to divergent selection regimes in adjacent plant populations. © 1983, The Genetical Society of Great Britain.