MOLECULAR POPULATION-GENETICS OF THE ARABIDOPSIS CAULIFLOWER REGULATORY GENE - NONNEUTRAL EVOLUTION AND NATURALLY-OCCURRING VARIATION IN FLORAL HOMEOTIC FUNCTION

The evolution of interspecies differences in morphology requires suffi cient within-species variation in developmental regulatory systems on which evolutionary forces can act. Molecular analyses of naturally occ urring alleles of the Arabidopsis thaliana CAULIFLOWER locus reveal co nsiderable intraspecific diversity at this floral homeotic gene, and t he McDonald-Kreitman test suggests that this gene is evolving in a non neutral fashion, with an excess of intraspecific replacement polymorph isms. The naturally occurring molecular variation within this floral r egulatory gene is associated with functionally different alleles, whic h can be distinguished phenotypically by their differential ability to direct floral meristem development.