Frequency and spatial patterning of clonal reproduction in Louisiana iris hybrid populations

The plant genera in which natural hybridization is most prevalent tend to b e outcrossing perennials with some mechanism for clonal (i.e., asexual) rep roduction. Although clonal reproduction in fertile, sexually reproducing hy brid populations could have important evolutionary consequences, little att ention has been paid to quantifying this parameter in such populations. In the present study, we examined the frequency and spatial patterning of clon al reproduction in two Louisiana iris hybrid populations. Allozyme analysis of both populations revealed relatively high levels of genotypic diversity . However, a considerable amount of clonality was apparent. Nearly half of all genets (47%) in one population and more than half (61%) in the other ha d multiple ramets. Furthermore, both populations exhibited relatively high levels of genetic structuring, a pattern that resulted from the aggregation of clonal ramets. The occurrence of clonal reproduction in hybrid populati ons could not only facilitate introgression through an increase in the numb er of flowering ramets per genet and/or the survivorship of early generatio n hybrids, but might also influence the mating system of such populations. Any potential increase in the selling rate due to cross-pollination among r amets of the same genet may, in turn, increase the likelihood of homoploid hybrid speciation.