Association of Southeastern Biologists

J. Kenneth Shull, Jr.
Professor Emeritus
Ph.D., Florida State University

Most families of flowering plants undergo polyploid evolution, in which various species hybridize, their chromosomes fail to pair during meiosis and the resulting hybrid is sterile. The chromosomes subsequently double, restoring fertility, but now the hybrid is polyploid. An exception to this is the genus Lilium, where all but one of the 140 or so species is diploid. Even in this genus, some interspecific hybrids are sterile, with the chromosomes failing to pair. Lilium x 'Black Beauty' is a hybrid between L. speciosum and L. henryi, in which the chromosomes have greatly reduced pairing in meiosis. We are trying to determine if the pairing is between homologous chromosomes, or parts of chromosomes, or if it is completely random. Partial homology is very rare, or non-existent in most hybrids, and if this pairing is partially homologous, as it appears to be, it may lead to an understanding of how whole genomes (chromosome sets) evolve so that they no longer can pair in meiosis.

An undergraduate research project has led to a quite unexpected result. In an experiment to establish the importance of wing vibration in courtship of Drosophila melanogaster two undergraduates discovered that the females of several inbred stocks with various wing mutations selected males of the same stock over males of other stocks, and in some cases, even wild-type males. This is in spite of the males of these stocks not being able to make the courtship "song" due to the wing mutations. We are in the process of investigating mating behavior itself, the underlying genetics of this behavior, the evolutionary consequence of inbreeding, and the reliability of population experiments using these stocks.