The Variation Problem: The Gene Flow‐variation Hypothesis

Summary Phenotypic variation is as poorly understood as it is ubiquitous. Many biologists hold simplistic and even contradictory views of the relation between genic diversity and phenotypic variation. The correlation of electrophoretically detectable enzyme polymorphisms and morphological variation in island populations of lizards is described. A model explaining the different levels of genetic‐phenetic variation among the populations is suggested by a multiple regression analysis. The principal conclusions are that gene flow between habitats significantly elevates variation, and isolation by distance results in a variation asymptote.