Abstract Detail

Crops and Wild Relatives

Pascual, Mariana [1], Rieseberg, Loren [1].

Gene flow in the silverleaf sunflower, Helianthus argophyllus.

Gene flow plays an important role in evolutionary diversification. At high levels, it maintains genetic cohesion within a species or among populations, while reducing the potential for local adaptation, range expansion, and speciation. By contrast, reduced gene flow facilitates the independent evolution of populations or species, whether via natural selection or genetic drift. In plants, flowering time is a key determinant of the degree of gene flow and assortative mating within and among populations. The silverleaf sunflower, Helianthus argophyllus, is an annual Texas endemic that is the sister to H. annuus, the progenitor of the domesticated sunflower. The two species diverged circa 1.5 million years ago, and H. argophyllus has been the most important wild donor of agronomically important alleles to the cultivar. While H. annuus is a widespread species found across central and western Northern America, H. argophyllus is restricted to the Texas coastal plain and barrier islands in the Gulf of Mexico. Despite its very limited geographic distribution, H. argophyllus exhibits two flowering syndromes that are associated with geography and water availability, and correlated with other plant traits (e.g. floral size characters, height, and branching): some individuals flower in late summer and are relatively short (early flowering syndrome), while other individuals delay flowering in favor of growth until fall (late flowering syndrome). The late flowering syndrome is characteristic of coastal and inland populations, where drier conditions prevail; it also represents about half of the flowering syndromes exhibited in barrier island populations. About 50% of plants from the barrier islands display the early flowering syndrome, where it is exclusively found. I will estimate the effects of the phenological differences on contemporary gene flow by comparing within versus between genotype matings, through parentage analyses of populations in the field in two different years as well as through pollen competition experiments. In addition to insights regarding the earliest stage of differentiation and potentially speciation, studies of flowering time variation in H. argophyllus are likely to provide useful insights into the mechanisms by which natural populations escape, avoid or resist water deficit.

1 -
2 - University of British Columbia, 3200-6270 University Blvd., Vancouver, British Columbia, V6T 1Z4, Canada

Flowering time
assortative mating
crop wild relatives.

Presentation Type: Poster This poster will be presented at 5:30 pm. The Poster Session runs from 5:30 pm to 7:00 pm. Posters with odd poster numbers are presented at 5:30 pm, and posters with even poster numbers are presented at 6:15 pm.
Number: PCW011
Abstract ID:868
Candidate for Awards:None

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