Phylogenetic relationships and historical biogeography of melanotaeniid fishes in Australia and New Guinea

Abstract

Phylogenetic analysis of melanotaeniid mtDNA cytochrome b and tRNA ^Pro-control region sequence is broadly consistent with the current taxonomy. However, the molecular phylogeny supports the elevation of M. s. australis to full species status and indicates either that it is a composite species or has introgressed with sympatric Melanotaenia species. Phenotypically cryptic mtDNA diversity in north-eastern Australia possibly represents an undescribed species. Six major monophyletic clades present in the phylogeny were strongly supported by morphological data. The clades represent three biogeographic regions. Fish from northern New Guinea form a monophyletic clade, within which Melanotaenia and Glossolepis are polyphyletic. The divergence of this clade from those in southern New Guinea is consistent with the final uplift of the Central Highlands 5 million years BP. North-western New Guinea and associated islands represent another highly divergent, monophyletic clade of a similar age to that in northern New Guinea. The remaining four clades form a monophyletic assemblage restricted to southern New Guinea and Australia: one in northern Australia, one with a disjunct distribution in north-western and eastern Australia, one widespread throughout Australia and southern New Guinea, and one in southern New Guinea with an outlying species in northern Australia. The phylogenetic relationships between Australia and southern New Guinea are consistent with episodic connection via the freshwater Lake Carpentaria during periods of low sea level.