[Ann Sakai] [Stephen Weller] [Research-Dioecy] [Research-Heterostyly] [Research-Conservation]

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Sakai/Weller Lab

Evolution of Plant Breeding Systems: Heterostyly

Evolution of heterostyly.  Several plant families exhibit a breeding system known as heterostyly, where plants in the population have two or three floral morphs that differ in the relative positions of the stigma and stamens in the flower.  Outcrossing is encouraged in this system because pollen flow tends to occur between morphs that have styles and stamens at the same height, and pollination between stigmas and stamens at different heights is decreased by the floral morphology.   Incompatibility reactions also prevent fertilizations from occurring when pollination occurs between anthers and stigmas at different levels. Self-pollination and matings among plants with the same morph are usually prevented by these incompatibility relationships and the morphological differences between flowers.  In Oxalis alpina populations occurring in the southwest United States and northern Mexico , either three floral morphs (shorts, mids, and longs, referring to the position of the stigma) or two floral morphs (shorts and longs) occur in populations.  We are interested in conditions that have resulted in loss of the mid morph, and modifications of incompatibility that may have contributed to loss of the mid morph.  In collaboration with César Domínguez, Francisco Molina-Freaner, and Juan Fornoni, investigators at the National Autonomous University of Mexico, as well as Travis Glenn and Olga Tsyusko at the Savanna River Ecology Laboratory,  we are conducting field and molecular work to determine selective factors that have led to the breakdown of tristyly in this species.  Graduate student Jennifer Weber is investigating how fertility of the mid morph influences the frequency of this morph in populations.