Genetic Diversity of Natural-Populations of Acacia auriculiformis

Abstract

Seeds from 18 populations of Acacia auriculiformis A. Cunn. ex Benth. from natural riverine and coastal forests in Australia and Papua New Guinea were electrophoretically analysed at 22 isozyme loci representing 17 enzyme systems. Genetic variability measures were determined using 12 isozyme loci. On average, 39.8% of the loci were polymorphic (0.99 criterion). Average and effective numbers of alleles per locus were 1.5 and 1.1 respectively. Mean expected heterozygosity was 0.081 with values ranging from 0.002 (South Alligator River, Northern Territory) to 0.180 (North Mibini, Papua New Guinea). The genetic differentiation between populations was high (G_ST = 0.270), indicating that about 73% of the isozyme variation was among progenies within populations. Hence, both intra- and inter-population genetic variations are important in initial selections in A. auriculiformis improvement programs.

Nei's unbiased genetic distance between populations ranged from 0.000 to 0.120, with populations from the Northern Territory, Australia, generally being very closely related to each other. UPGMA cluster analysis using Nei's unbiased genetic distance revealed three distinct clusters of populations corresponding to the geographic distribution of the species in the Northern Territory and Queensland, Australia, and Papua New Guinea. Populations from Queensland were closely related to populations from Papua New Guinea rather than to populations from the Northern Territory, which is in the same land mass.