XVI International Botanical Congess

Replicate hybrid zones with a diversity of recombinant genotypes of varying age offer increased resolution for genetic mapping experiments, whilst expanding the pool of organisms amenable to genetic study beyond model lab species. We studied 3 natural hybrid zones between Helianthus annuus & H.petiolaris, two species which have given rise to at least one extant hybrid species. Using 88 markers from 17 chromosomes, we analyzed the introgression of chromosomal segments of H. petiolaris into H. annuus. Introgression was significantly reduced relative to neutral expectation for 26 such segments, suggesting that each contains one or more factors contributing to isolation. In addition, comparing rates of introgression across collinear vs rearranged chromosomes suggests nearly 50% of the barrier to introgression is due to chromosomal rearrangements.