Plant & Animal Genome IX Conference

Workshop: Compositae
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THE ROLE OF CHROMOSOMAL REARRANGEMENTS IN SPECIATION: INSIGHTS FROM GENETIC MAP-BASED STUDIES OF SUNFLOWER HYBRIDS

Biology Department, Indiana University, Bloomington, IN 47405

Several authors have proposed that speciation frequently occurs when a population becomes fixed for one or more chromosomal rearrangements that reduce fitness when heterozygous. This hypothesis has little theoretical support because mutations that cause a large reduction in fitness can only be fixed in small, inbred populations. Moreover, some chromosomal rearrangements do not cause fitness reductions. I will present data from three synthetic introgression lines and three natural hybrid zones of Helianthus annuus x H. petiolaris to show that rearrangements reduce interspecific gene flow more by suppressing recombination and extending the effects of linked isolation genes than by reducing fitness. This unorthodox perspective has significant implications for speciation models and for the outcomes of contact between neospecies and their progenitor(s).