THE GENETICS OF FLORAL DEVELOPMENT DIFFERENTIATING 2 SPECIES OF MIMULUS (SCROPHULARIACEAE)

Investigation of the developmental processes responsible for the evolu tion of the small-flowered, highly selfing Mimulus micranthus from its large-flowered, mixed-mating progenitor M. guttatus, revealed M. micr anthus to have both a shorter duration and a higher rate of bud develo pment. Hence flowers of M. micranthus can be considered as progenetic forms of M. guttatus. Genetic analysis of F-1, F-2 and backcross gener ations derived from the cross M. micranthus x M. guttatus provided no evidence for major gene control of development processes responsible f or differentiating the two taxa. Furthermore, F-2 segregation patterns suggest that duration and rate of development may be genetically inde pendent of one another. Hence, the evolution of small-flowered selfing taxa in Mimulus may reflect selection for rapid development.