Distyly

[2] Specifically these plants exhibit intra-morph self-incompatibility, flowers of the same style morph are incompatible.

The first scientific account of distyly can be found in Stephan Bejthe's Caroli book Clusii Atrebatis Rariorum aliquot stirpium [5].

Charles Darwin popularized distyly with his account of it in his book The Different Forms of Flowers on Plants of the Same Species.

In a study of Primula veris it was found that pin flowers exhibit higher rates of self-pollination and capture more pollen than the thrum morph.

The hemizygotic nature of the S-locus has been shown in Primula [14] , Gelsemium,[16] Linum [17][15], Fagopyrum [18][19], Turnera,[13] Nymphoides[20] and Chrysojasminum.

[21] The S-morph of Fagopyrum contains ~2.8 Mb hemizygous region which likely represents the S-locus as it contains S-ELF4 which establishes female morphology and mating type.

[18][19] In Gelsemium, the S-locus is composed of four genes, GeCYP, GeFRS6, and GeGA3OX are hemizygous and TAF2 appears to be allelic with a truncated copy in the L-morph.

[16] GeCYP appears to share a last common ancestor (or ortholog) with the Primula S-gene CYPT.

The supergene evolved in a step-by-step manner, meaning each S-gene duplicated and move to the pre-S-locus independently of the others.

[30][32] GLOT , a MADS-BOX family member,[33] is the male morphology gene as it promotes corolla tube growth under the stamen.

[35] YUC6 is likely involved in auxin biosynthesis based on homology; it is the male self-incompatibility gene and establishes pollen size dimorphisms.