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 orbifolia was investigated for chloroplast DNA (cpDNA) and rDNA based on restriction 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 detected which were distributed over five haplotypes. Nucleotide diversity in the species was high and the majority of this diversity was distributed between populations with diversity within populations restricted to a single population. There was significant differentiation between the two regions in the species distribution with the Narrikup region being distinguished by a single haplotype that was characterized by six unique mutations. Variation in rDNA was detected with three gene length variants present in most individuals. However, the Narrikup region was characterized by homogenization of the gene unit to a single length variant in all individuals. The divergence of the Narrikup region suggests that the disjunction in the species distribution has been present for a long time and the two regions represent separate evolutionary lineages.