Cryptic Self‐incompatibility and the Breeding System of Clarkia Unguiculata (Onagraceae)

Analysis of 2,117 segregating progeny from competitive pollinations involving self and foreign pollen reveals that Clarkia unguiculata possesses a cryptic self‐incompatibility mechanism. This mechanism promotes outcrossing when foreign pollen is available, yet allows for high fecundity through selling in marginal or catastrophically reduced populations. Competitively based self‐incompatibility in the species suggests that discrimination against genetically similar siblings may also be possible. The preferential self‐exclusion system insures that a seed crop of maximal size and genetic heterogeneity will be produced despite unpredictable environmental perturbations.