Associations among Multiple Floral Polymorphisms in Linum pubescens (Linaceae), a Heterostylous Plant

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Abstract
Populations of distylous species contain two floral morphs that differ in the position of sexual organs and incompatibility relationships. In addition, secondary characteristics may distinguish flowers of the two morphs. Rarely, however, are color polymorphisms associated with the distylous syndrome. Linum pubescens is an annual, distylous, pink‐flowered species that is polymorphic for corolla throat color (yellow, purple) and pollen grain color (white, blue). The nine Israeli populations studied had 1:1 style morph frequencies and all were polymorphic for pollen and corolla color. The frequency of the floral variants differed between the four northern Galilee populations and the five Judean populations. Significant nonrandom associations existed among the three floral traits. Both morphs in Judean populations were more likely to produce white pollen and yellow corollas. In Galilee populations, the short morph was significantly associated with purple corollas and blue pollen, while the long morph produced yellow corollas and either pollen color. Overall, 75% of flowers with purple corollas produced blue pollen, while yellow flowers tended to produce white pollen. Despite the potential for having an effect on reproductive success, the style length and color polymorphisms were not associated with individual flower size, flower number, fruit and seed production, or seed mass. It is likely that isoplethic morph ratios and nonrandom spatial structure result in the maintenance of disassortative pollination regimes within natural populations.