XVI International Botanical Congess

Heterostyly is a genetic polymorphism in which plant populations are composed of two (distyly) or three (tristyly) morphs that differ reciprocally in the heights of stigmas and anthers in flowers. The polymorphism has evolved independently in at least 28 angiosperm families. Recent work on heterostyly has illustrated the diversity of ways that the syndrome can be expressed and the contrasting evolutionary pathways by which it can be modified to other breeding systems. Experimental studies of the pollination and mating process in heterostylous populations have demonstrated that the polymorphism functions to promote proficient pollen dispersal between plants by animal pollinators. Despite the use of heterostyly as a model system for addressing many issues in genetics, evolution and population biology controversy still exists concerning the origins of heterostyly and the order of establishment of morphological and physiological traits in the syndrome. In addition, little is known of the molecular and developmental genetics of heterostyly. Current research on these topics is reviewed.