Comparative phylogeography and population genetics of three banded iron formation endemics

[Truncated] The Yilgarn Banded Iron Formations (BIFs) of south-western Australia are terrestrial islands embedded within the largest remaining stand of Mediterranean woodland on Earth. These ancient geological features are centres of high species richness, turnover and endemism - characteristics attributed to the diversity of niche habitats provided by their topographic complexity as well as historical factors, including an absence of glaciation since the Permian (250 million years ago (Ma)). The BIFs to the south west of the Yilgarn province, along the boundary of the South Western Australian Floristic Region, are particularly notable for their high endemism and many species here occur across several formations, reminiscent of an oceanic island archipelago. It is not known to what extent these disjunct BIF populations have been historically connected by population expansion and contraction, or by long distance dispersal events, or whether they have been isolated for long periods of time as found in taxa endemic to granitic terrestrial islands. Regional BIF endemics provide an excellent opportunity to assess population genetic connectivity, or lack thereof, using phylogeographic and population genetic approaches.
I selected three taxa for phylogeographic and population genetic analysis that a) appeared to show limited dispersal capability, b) occurred across five or more Yilgarn BIFs within the same region and did not occur in the intervening landscape and c) were unrelated, so any congruence in phylogeographic patterns between the taxa could not be ascribed to phylogenetic relatedness. These taxa are:
1 ) Atelomastix bamfordi - a spirostreptid millipede that is restricted to pockets of moist habitat provided by the shady gullies and areas of dense leaf litter, present on five of the Yilgarn BIFs. Unlike its congeners found in the wetter south-western corner of the continent, A. bamfordi was often difficult to find.
2 ) Grevillea georgeana - a proteaceous perennial shrub that is restricted to banded ironstone and was sampled from seven Yilgarn BIFs for the purposes of this study. The showy, red flowers of this attractive plant form a dominant food source for several species of honeyeater pollinators. The species can be common where it occurs but on some BIFs persists only as very small populations.
3 ) Banksia arborea - formerly known as Dryandra arborea and commonly known as the Yilgarn tree, is a conspicuous element of the BIF flora and was sampled from eight Yilgarn BIFs. This insect and bird pollinated species has a broader habitat requirement than either A. bamfordi or G. georgeana and occurs anywhere from the exposed summits of outcrops to the shale and sandy slopes lower down.