Print PageVariation in plant reproductive strategies exceeds that of any other group of organisms, thus understanding how mating systems evolve has been of interest to many biologists. Within the genus Mimulus, there is wide variation among species in mating system, flowering time, and antiherbivore traits. Previous studies with Mimulus guttatus have identified correlations among traits associated with self-fertilization, reduced antiherbivore defense, and early flowering. I estimated correlations and phenotypic selection in six traits in 200 plants from a field population of Mimulus guttatus to test whether previously reported trait combinations associated with selfing were observed, and if so, whether they were adaptive.
Results/Conclusions
Six of 15 (40%) predicted phenotypic correlations were statistically significant, although all but one of these were opposite of the predicted sign. In multivariate models, I found significant direct linear selection favoring early flowering, large flowers, and rapidly closing stigma lobes, and no evidence for stabilizing or disruptive selection. Selection for flower size and flowering time, however, was negatively correlated, suggesting divergent selection in which adaptive phenotypes had large flowers and flowered early or had small flowers and flowered late. For these traits, adaptive phenotypes therefore contrast with predicted patterns, as well as observed patterns among taxa within the genus. Correlated selection opposing predicted trait combinations may help maintain phenotypic and mating system variation in this population.
