Genetic Structure of Natural Populations of Wild Sunflowers (Helianthus annuus L.) in Australia

Abstract

The genetic structure of 11 wild populations of H. annuus occurring in New South Wales and Queensland was determined by isozyme analysis. Considerable isozyme diversity was found among loci within and between populations, with three to five alleles being identified at each of 10 loci. Mean levels of heterozygosity ranged from o· 19 to O· 38 and gene diversity values from 0·29 to O· 52. In all populations Wright's fixation indices were positive (0·09-0· 51) suggesting a degree of inbreeding. Differences in the level of genetic differentiation between populations were not correlated with geographic distance. Indeed, notable genetic diversity was detected between six sites occurring within a 2-km radius of Gunnedah, N.S.W., where the genetic distance relationships were D = 0·13 ± 0'08, the same as those between popUlations throughout the region.