A paper on the intraspecific phylogeny of the damsel fish Pomacentrus moluccensis was published the other day by Joshua Drew and Paul Barber as a short communication in Molecular Phylogenetics and Evolution. This paper is well worth reading as it demonstrates that specimens from Fiji form a monophyletic sister group to those from further west. Vanuatu species are also monophyletic, while those from the Solomons to Sumatra form a third, most derived clade.
What makes this interesting is that this runs counter to the traditionally accepted mode of dispersal in the Pacific, where the area around New Guinea and Indonesia act as a source area for the remainder of the Pacific.
As the authors point out, this story is based only on mitochondrial DNA sequences, and as such only tell a partial story of P. moluccensis' history. More data may change the story somewhat, but the results published here are intruiging and will hopefully stimulate further investigation.
Drew, J., and Barber P. H. (2009) Sequential cladogenesis of the reef fish Pomacentrus moluccensis (Pomacentridae) supports the peripheral origin of marine biodiversity in the Indo-Australian archipelago. Molecular Phylogenetics and Evolution. 53(1): 335-339.
Picture stolen from the Encyclopedia of Life (http://eol.org/pages/212092)