9703853 Arnold We will test the role of natural selection in the production and survivorship of hybrid Louisiana irises. Our analyses will include experimental crosses within and between the species Iris fulva and Iris brevicaulis to produce various hybrid and parental seeds. These seeds will then be placed into both greenhouse and natural environments. The germination, survivorship, growth to maturity and reproductive capacity of the hybrid and parental individuals will then be monitored and compared. The hybrid plants will be assigned to specific categories using numerous molecular (i.e., DNA) markers. These analyses will thus allow an estimate of the fitness of both parentaland hybrid plants. These estimates can then be used to predict the long-term effects that natural hybridization between different iris species may have on the genetic diversity and evolution of this plant species complex. Natural hybridization between individuals belonging to different genera, species or subspecies has been recognized as a fundamentally important process in the evolution of many plants. Indeed, it has been estimated that over half of all flowering plant species (i.e., Angiosperms) have originated from ancient or more recent hybridization events. Furthermore, it has recently begun to be appreciated that natural hybridization and subsequent exchange of genes between the hybridizing groups can be equally important for animals as well. Our studies of the Louisiana irises will allow a detailed examination of this fascinating and important process. In particular, these studies will help define the role of natural selection in determining the evolutionary consequences of natural hybridization.
