Population Genetics of Echium plantagineum L.Target Weed for Biological Control

Abstract

Eight Australian and two European populations of E. plantagineum were surveyed for their genetic structure at 16 variable isozyme loci. On average, the Australian and European populations possessed 2�7 and 2�6 alleles per locus, a gene diversity of 34 and 35% and heterozygosity of 32 and 29% respectively. Estimates of the outcrossing rate in one Australian population were 61 and 73% for mean single-locus and multi-locus methods respectively. The levels of genetic diversity detected in this species consistently exceed those detected in a range of other species that occupy a similar stage in succession or that have similar breeding systems. Moreover, contrary to expectation, genetic diversity was equally great in the colonial populations in Australia as in European-source populations. If this high level of isozyme diversity reflects the diversity likely to be found in other parts of the genome, attempts to achieve substantial biological control may require the use of many different control agents.