Ontogenetic evolution and speciation in Mimulus cardinalis and M. lewisii (Lamiales)
The floral ontogenies of three populations of 'M. cardinalis' were compared, as were the floral ontogenies of both races of 'M. lewisii '. This was done to compare the floral ontogenies, of each species as exemplified by populations from Yosemite National Park, CA, and interpret differences as evolutionary transformations that occurred during speciation of 'M. lewisii' from an 'M. cardinalis'-like ancestor. Between the species, differences in corolla shape were observed shortly after corolla tube formation. Corollas in buds of 'M. lewisii ' became dorso-ventrally narrow while those in buds of 'M. cardinalis' became laterally narrow. The shorter stamens and style in flowers of 'M. lewisii' were the result of early terminations of growth relative to the growth of those in flowers of 'M. cardinalis'. The changes in ontogeny that had the largest impact on floral form are hypothesized to have occurred at late stages, while a series of smaller changes occurred throughout development.