Genetic diversity within and between natural Populations of Eucalyptus occidentalis (Myrtaceae)

Eucalyptus occidentalis is endemic to the south-west of Australia, occurring in small isolated populations in wet depressions and along drainage lines. The level of genetic diversity and pattern of structuring within and between populations was investigated using nuclear RFLP analysis of 10. populations. The level of genetic diversity was moderate and similar in the populations from the main range but lower in the outlier populations from the eastern end of the range. There was no evidence of inbreeding within the populations. The level of population differentiation was low but significantly different from zero, and the populations from the eastern end of the range showed higher levels of differentiation from each other and from the populations in the main range. The pattern of genetic diversity in E. occidentalis indicates historical connectivity between populations and the species was probably more abundant with a wider distribution in the past, except for the eastern end of the range where the species distribution appears to have always been fragmented. The pattern of population differentiation is similar to the pattern of differentiation in quantitative traits that has been observed in provenance trials. Sampling strategies for breeding programs should focus on the main range of the species.