Divergence in the chloroplast genome and nuclear rDNA of the rare Western Australian plant Lambertia orbifolia Gardner (Proteaceae)

The population genetic structure of the Australian plant Lambertia orbifoli a was investigated for chloroplast DNA (cpDNA) and rDNA based on restrictio n fragment length polymorphism. Variation was assessed in 14-20 individuals from six populations with probes covering the majority of the chloroplast genome and the whole rRNA gene unit. For cpDNA, eight mutations were detect ed which were distributed over five haplotypes. Nucleotide diversity in the species was high and the majority of this diversity was distributed betwee n populations with diversity within populations restricted to a single popu lation. There was significant differentiation between the two regions in th e species distribution with the Narrikup region being distinguished by a si ngle haplotype that was characterized by six unique mutations. Variation in rDNA was detected with three gene length variants present in most individu als. However, the Narrikup region was characterized by homogenization of th e gene unit to a single length variant in all individuals. The divergence o f the Narrikup region suggests that the disjunction in the species distribu tion has been present for a long time and the two regions represent separat e evolutionary lineages.