12/10/2011
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Australasian robins rocked

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Scarlet Robin is one of the forms that remains intact in the latest analysis. Photo: JJ Harrison (commons.wikimedia.org).
Scarlet Robin is one of the forms that remains intact in the latest analysis. Photo: JJ Harrison (commons.wikimedia.org).

A new comprehensive genetic survey highlights the differences between Papua New Guinean 'chats' and 'flycatchers' and those in Australia, as well as within-continent.

The 'robins' of Australasia, Papua New Guinea and its associated islands are known for their extreme similarity to the true chats and flycatchers of the Northern Hemisphere. However, this is due to convergent evolution and the Petroicidae has had a prolonged evolutionary history, actually apparently deriving from a basal form close to the ancestor of most of the world's oscine or perching birds, and further evidence for an Australian origin for the passerines.

A joint Australian/Swedish team analysed two mitochondrial and one nuclear gene from 40 of the 46 currently recognised species, including endemic island forms, taking in all 14 genera. Each gene produced the same six clades, despite the relatively similar appearances of the birds. appearance is one of the keys here, as the lineages matched those produced by a previous morphological analysis fairly well, and also correlated with a less comprehensive earlier genetic analysis.

However, differences include the separation of the Eopsatrinae and Petroicinae subfamilies, the forest-specialising 'yellow robins' and the largely black-, red- or pink-plumaged 'Australian robins', generally found in more rocky habitats. The team recommends treating all six groups as separate subfamilies.

The treatment highlights the more deep divisions between New Guinean forms, as well as confirming the geographical barriers within Australia that partly cause speciation, particularly the Carpentarian Barrier in northern Australia which has created 'taxonomic breaks' in much of the continent's avifauna. Species level divergence certainly occurs between Papua New Guinea and Australia forms, and this was seen in the genes of Yellow-bellied Flycatcher, Northern Scrub-robin, Ashy and Grey-headed Robin (already split in some quarters), and White-faced Robin.

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The authors discuss the use of subgenera to further elucidate the group's relationships, though this idea is controversial. However, their analysis also suggests potential splits in Yellow-bellied Flycatcher, producing at least two species from six distinct subspecies in Australia and New Guinea, and New Guinean Scrub-robin from Northern. Northern and Southern Yellow-robin may be re-split, but the subspecies do not actually correspond with the genetic story at present, and the Northern Territory form of Hooded Robin appears to be distinct.

It is likely that other changes may be slowly adopted or remain dormant until further specimens have been sampled.

Reference
Christidis, L, Irestedt, M, Rowe, D, Boles, W E and Norman, J A. 2011. Mitochondrial and nuclear DNA phylogenies reveal a complex evolutionary history in the Australasian robins (Passeriformes: Petroicidae). Molecular Phylogenetics and Evolution doi.10.1016/j.ympev.2011.08.014.