Gene Flow in Seed Plants

Abstract

Gene dispersal (flow, or migration) within and between plant populations has been of continuous interest to plant breeders and seed producers for many decades. Economic considerations have stimulated studies of gene flow as a function of distance, breeding system, pollinating agent, and planting design in numerous domestic plants. Only during the past two decades have a large body of plant evolutionists become interested in information accruing from these studies, and in the rates of gene flow in wild populations. Their efforts have concentrated primarily on related problems such as adaptations for and mechanics of pollen and seed (or fruit) dispersal, plant-pollinator coevolution, adaptive radiation in pollination and seed dispersal mechanisms, and colonization and the alteration of species boundaries. Early in this century, anecdoctal evidence on the movement of pollen and seed vectors, dispersal of pollen by wind, and the range extensions of weed species led to the casual assumption that gene flow must be extensive, and that it must play a major role in the cohesion of populations and population systems. This view eroded as more information became available and was more critically interpreted (e.g., Grant, 1958, 1971; Ehrlich and Raven, 1969; Stebbins, 1970a; Bradshaw, 1972).