Phylogeography, classification and conservation of pink zieria (Zieria veronicea; Rutaceae): influence of changes in climate, geology and sea level in south-eastern Australia

We assessed genetic variation in the Australian shrub Zieria veronicea across its current distribution and used environmental niche modelling to predict its distribution at the Last Glacial Maximum (LGM). The species range, from Kangaroo Island in South Australia to northern Tasmania, includes substantial overland and marine disjunctions of up to similar to 500km. By inferring historical patterns of connectivity and genetic differentiation from DNA sequences and AFLP data, we aimed to provide new insight into the history of the species-rich sclerophyll vegetation in south-eastern Australia. Genetic differentiation of populations was not correlated with the size of geographic disjunctions. The deepest genetic divergence was between populations on Kangaroo Island and the adjacent mainland, separated by a strait only 13km wide. Populations in western Victoria and Tasmania, separated by the 300km of Bass Strait, showed the lowest genetic differentiation. This pattern is consistent with dispersal of Z. veronicea into Tasmania, across the Bassian Plain, possibly as recently as the LGM, in line with inferred distribution at that time. Genetic patterns, soil ages and niche models support Quaternary colonisation of the lower Murray Basin, potentially from eastern South Australia. The history of a large (500km) disjunction between populations in western and eastern Victoria is unclear; historical connectivity of populations through suitable habitats is assumed, but the timing and location of connections are not clear. Genetic data support the current recognition of two subspecies and their treatment as distinct entities under conservation legislation.