Symmetry is an important floral character and is often associated with the degree of pollination specialization. Typically floral symmetry is fixed within a species. Rotational symmetry occurs in two different corolla variations according to the direction in which the petals overlap. This study describes the pattern of polymorphism in corolla chirality of Hypericum irazuense Kuntze ex. N. Robson and H. costaricense N. Robson. The individuals of these species exhibit flowers with corollas that rotate either counter clockwise (left/sinistrorse) or clockwise (right/dextrorse). Studying this pattern of floral expression is the first step in gaining a better understanding of whether this trait polymorphism is maintained due to an adaptive advantage or as a byproduct of a developmental genetic constraint. We quantified the proportion of dextrorse and sinistrorse flowers for H. irazuense and H. costaricense. We also examined whether the chirality of a flower is independent of the corolla chirality of its neighbor flower at the ultimate branch level, i.e., a group of terminal branches that are connected by the same node. We demonstrate that the proportion of sinistrorse and dextrose flowers is equal among individuals within a population of H. irazuense and H. costaricense. In addition, we show that in these populations, the forms are randomly distributed at the ultimate branch level indicating that the identity of a flower type is not determined by the chirality type of its neighbor flower. The 1∶1 proportion of chirality types among individuals suggests that the maintenance of both flower forms may convey a reproductive benefit. But, the random distribution of flower type at the ultimate branch level challenges this interpretation. Further studies are needed to address the adaptive significance, if any, of this pattern of dextrorse and sinistrorse flowers.
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