Phylogeography and conservation of three oil mallee taxa, Eucalyptus kochii ssp kochii, ssp plenissima and E-horistes

Eucalyptus kochii ssp. kochii, ssp. plenissima and E. horistes are planted for eucalypt oil production and land rehabilitation in Western Australia. Variation in cpDNA was investigated by RFLP analysis of 10 populations across the distribution of the three taxa. Diversity in the chloroplast genome was high, with most of the diversity distributed between populations. The three taxa formed a cohesive group that was clearly differentiated from E. oleosa, which was used as an outgroup. There was some differentiation of E. kochii ssp. kochii from E. kochii ssp. plenissima and E. horistes. Several mutations specific to the E. kochii ssp. kochii, ssp. plenissima and E. horistes haplotypes were present in a variant of E. oleosa, suggesting that introgression has occurred. Congruence between cp gene genealogy and geographic distribution was consistent with limited maternal gene flow between populations. There was little structuring of haplotype diversity and the pattern of variation in the cp genome was congruent with that previously detected in the nuclear genome.