Phylogeography of the Indo-Pacific parrotfish Scarus psittacus: isolation generates distinctive peripheral populations in two oceans

Phylogenetic, phylogeographic, population genetic and coalescence analyses were combined to examine the recent evolutionary history of the widespread Indo-Pacific parrotfish, Scarus psittacus, over a geographic range spanning three marine biogeographic realms. We sequenced 164 individuals from 12 locations spanning 17,000 km, from 55A(0)E to 143A(0)W, using 322 base pairs of mitochondrial control region (D-loop). S. psittacus displayed high haplotype (h = 0.83-0.98), but low nucleotide (< 1%) diversity. Most (> 83%) genetic variation was within populations. AMOVA revealed significant partitioning and identified five geographic groups. These included one central population and four populations peripheral to the centre. The central population occupied reefs from Western Australia to Tahiti and represented the central Indo-Pacific biogeographic realm. Cocos Keeling was distinct from central and western Indo-Pacific biogeographic realms occupying a position intermediate to these. Peripheral populations (Hawaii, Marquesas) represented the eastern Indo-Pacific biogeographic realm, while Seychelles represented the western Indo-Pacific biogeographic realm. All but the central population expanded (< 163 kya). Whilst all populations experienced major sea level and SST changes associated with Pleistocene glaciation cycles, the genetic structure of the central population was relatively homogenous unlike the remaining genetically distinctive populations.