XVI International Botanical Congess

Natural hybridization has been viewed as either a creative process or an evolutionary dead end. In the first half of this century, Edgar Anderson argued that introgressive hybridization (i.e., the exchange of genetic material between hybridizing taxa) could lead to (i) the transfer or de novo origin of adaptations and (ii) the origin of hybrid taxa. Anderson used the Louisiana Irises as a paradigm for the evolutionary outcome of hybridization in nature. We have found evidence that these species are indeed an example of the evolutionary significance of natural hybridization. In this talk, I will highlight (i) restrictions to gene flow between these species, (ii) fitness estimates for hybrid and parental genotypes under natural and experimental conditions, and (iii) the outcome of hybridization among the Louisiana Iris species with regard to gene exchange and speciation.