Polymorphism and geographic variation of flower color in chilean populations ofEschscholzia californica

Abstract

In twelve populations ofEschscholzia californica from central Chile, where it was introduced in the latter part of the 19th century, there is a regular gradient in frequency of the allelesJ andj, which control orange vs. yellow flowers, ranging from a maximum value of 0.531 to a minimum of 0.160 forJ. Populations having higher values ofJ occupy more mesic sites. In addition, the great majority of the populations have significant excess of heterozygotes over those expected on the basis of theHardy-Weinberg equilibrium, and so exhibit balanced polymorphism for theJ-j pair of alleles, probably associated with heterosis ofJj genotypes. Evidence is presented which suggests that this locus serves as a marker for adaptative gene complexes rather than being itself associated with adaptation. In Chile, the association ofJJ genotypes with cooler, moister habitats is the opposite of the condition existing in California, and suggests that extensive reorganization of the gene pool, through changed linkage relationships, took place asE. californica populations were being established in Chile.