Correlated Evolution in Floral Morphology and the Timing of Self‐Compatibility inLeptosiphon jepsonii(Polemoniaceae)

The timing of self‐compatibility was found to vary within and among populations of Leptosiphon jepsonii, a narrowly distributed California annual species. In each of 17 populations, some individuals exhibited transient self‐incompatibility, a phenomenon that confers delayed selfing, while others were fully self‐compatible upon flower opening, allowing for concurrent self‐ and cross‐fertilization. The frequency of initially self‐compatible individuals varied significantly among populations, ranging from 3.2% to 71.0%. A comparison of outcrossing rate estimates for three populations was consistent with the hypothesis that early self‐compatibility promotes higher selfing rates. Population means for each of three floral morphological traits were significantly correlated with a population index of self‐incompatibility that reflects the frequency of fully self‐compatible and transiently self‐incompatible individuals. A high frequency of self‐compatibility was associated with shorter corolla tubes, smaller corolla lobes, and greater overlap of stigma and anthers. The demonstration of this relationship among populations within a small geographic range suggests fine‐scale local adaptation of mating system traits in L. jepsonii.