Evolutionary genomics of plant adaptation and speciation

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How frequent is cross-species mating or hybridization? What happens to the boundaries between species following hybridization? Can hybridization sometimes contribute to the formation of new traits or new species? Also, what is the genetic basis of the hybrid vigour often seen when genetically different plants or animals are crossed? These are the basic biological questions we will tackle. We will analyze the effects of hybridization on barriers that prevent the movement of genes between wild sunflower species. Evolutionary biologists once believed that for species to form, barriers to gene flow must be absolute. However, it now appears that some parts of the genome may be protected from interspecific gene flow, while others are not. A fundamental question to be addressed by this proposal concerns the degree of protection provided by individual "speciation" genes. Hybridization between species is also sometimes viewed as a stimulus for adaptation. We will test whether hybrid combinations of genes have facilitated the adaptation of the puzzle sunflower to salty habitats. We also will pinpoint the genetic changes responsible for hybrid vigour in wild and cultivated sunflowers. This genetic information will facilitate efforts to breed salt tolerant sunflowers and to increase yields from hybrid breeding programs in sunflowers and other crops. Finally, building on databases of genes for plant and animal species, we will search for the genetic signature of both recent and ancient hybridization. These analyses promise to yield paradigm-shifting results about the ubiquity of hybridization in evolution.