REU: Natural Selection, Breeding Structure and Hybridizationin Louisiana Irises

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In this study, Dr. Michael Arnold and his colleagues will analyze natural hybridization between the Louisiana iris species, I.fulva and I.hexagona. The genetic interaction between these two species has been used as the classic example of the process of interspecific gene flow. In order to study the pattern of transfer of genetic material between these two species, the investigators have established an experimental hybrid population in southern Louisiana. Individuals of I. hexagona were introduced into a natural population of I. Fulva and were allowed to flower during the spring of 1990. Leaf material and seeds have been collected from each of the flowering individuals of both species. Genetic markers that are diagnostic for either I. fulva or I. hexagona will be examined using material isolated form the leaf and seed samples. This will allow a test to determine whether or not hybrids have been formed and whether hybridization occurs bi-directionally (ie., with I. fulva and I. hexagona acting both maternal and paternal parents). These data will allow an estimate of the effects of natural selection on hybridization between these two species by comparing the proportion of interspecific versus intraspecific offspring that are produced.