GENETIC DIFFERENTIATION IN NATURAL-POPULATIONS OF GREVILLEA-ROBUSTA

Genetic variation in 23 natural populations of Grevillea robusta A.Cun n. from across the natural range of the species was examined using 20 isozyme loci assayed in young seedlings. Mean expected heterozygosity per population, H-e, varied from 0.080 to 0.131 with an average of 0.1 05. The genetic diversity of individual populations did not appear to be related to their ecological characteristics (araucarian vine forest or riverine habitat types) or their geographic locations. A genetic d istance analysis indicated a significant separation of the populations into two regional groups, eight from the northern part of the natural range and the remaining 15 from central and southern areas. Between-p opulation differences accounted for 17.9% of the total genetic variati on, one-third of which was attributable to the difference between the two regional groups. Most alleles at the 20 loci occurred across most or all of the geographic range. This, and the low level of genetic dif ferentiation between populations, suggest that genetic exchange betwee n populations has been maintained, despite the pattern of natural dist ribution of the species in small, separated populations.