Microgeographical Patterns of Allozyme Variation in Casuarina cunninghamiana Miq Within and Between the Murrumbidgee and Coastal Drainage Systems

Abstract

Within the Murrumbidgee drainage system, 100 seedlings from each of 14 populations of Casuarina cunninghamiana were assayed for their allozyme genotypes at 14 loci. The levels of genetic variation were fairly similar in all populations. There was no geographic clustering of populations based on genetic distance measures. Only 3.8% of the total genetic diversity could be apportioned among populations within the drainage system. In six additional populations, branchlets from 50 trees per population were assayed for their allozyme genotypes at 27 loci. Three populations were from the Murrumbidgee drainage system and each of the others from a different coastal drainage. The mean expected heterozygosities for coastal and inland zones were 0.139 and 0.093 respectively. Of the total genetic diversity 10.7% could be apportioned among the four drainages. The results of this study suggest that for in situ conservtion of C. cunninghamiana within a region, more emphasis should be placed on conserving one large population from each major drainage system rather than a number of populations within one or two drainage systems.