Genetic diversity and the insular population structure of the rare granite rock species, Eucalyptus caesia Benth

Abstract

There are 15 populations of E. caesia Benth. on granite rocks in south-westem Australia which include a total of about 2120 plants. The level of genetic variation at 18 allozyme loci in 13 populations was estimated. Seven loci were monomorphic for all plants assayed. At a majority of the 11 polymorphic loci the level of polymorphism was very low in most populations. Within populations the mean number of alleles per locus was 1.31 and the genetic diversity 6.8%. However, populations differed markedly in allelic frequencies at a number of loci. The genetic diversity within populations was remarkably low for a tree species but the level of population differentiation was the highest reported for any tree species. The data suggest that genetic drift may in part have been responsible for the low overall genetic diversity and the extensive population differentiation. The optimal strategies for conservation of the genetic resources of this valuable ornamental are considered in the light of the results of this study.