SCHWARZBACH, ANDREA E.1*, LISA A. DONOVAN2, DAVID M. ROSENTHAL2, and LOREN H. RIESEBERG3. 1Department of Biological Sciences, Kent State University, Kent, OH 44242; 2Department of Botany, University of Georgia, Athens, GA 30602; 3Department of Biology, Indiana University, Bloomington, IN 47405. - The role of transgressive segregation in hybrid speciation: an example from sunflowers.
Helianthus anomalus is a well characterized diploid hybrid
species occurring in several geographically isolated sand dune
habitats in Utah and Arizona. The parental species H. annuus
and H. petiolaris can be found in the same area but show
different habitat preferences. We are interested in the genetic bases
of adaptations that allow the hybrid to occupy habitats that are not
suitable to the parental species. Novel characteristics can slowly
evolve through mutational divergence or might be an immediate
byproduct of hybridization. One possible mechanism that generates
novel characteristics directly through hybridization is transgressive
segregation, which QTL studies explain through complementary gene
action. We have identified several morphological and ecophysiological
characters that are unique to the hybrid species. We have compared
artificial and natural hybrids to determine whether characters that
are unique to the natural hybrid species are present in artificial
hybrids.
Key words: Helianthus, hybridization, speciation, sunflowers, transgressive segregation