Saturday, 12 September 2009

The bizarre family of the Silktail

The silktail (Lamprolia victoriae) is a small bush bird, restricted to the Fijian islands of Vanua Levu and Taveuni. From its first description in 1874 its systematic position has been debated with suggested closest relatives ranging from the australian robins (Petroicidae), and the monarch flycatchers (Monarchidae), to the birds of paradise (Paradisaeidae). The late, great Ernst Mayr famously called the silktail "One of the most puzzling birds of the world". Last year, a group of european, american and south african scientists headed up by Martin Irestedt brought DNA evidence to the party to shed further light on the subject. Their results were published here.

What they discovered was totally unexpected. Their data suggests that the closest living relative to the silktail is the Papuan mountain drongo (PMD, Chaetorhynchus papuensis), a little-known bird of the New Guinea highlands. The PMD has traditionally been grouped with the drongos (Dicruridae), but in the Irestedt study, both the silktail and PMD are sister to the fantail family (Rhipiduridae).

The authors discuss at length the biogeographic implications of their finding, suggesting either long distance dispersal or a vicariant metapopulation origin, but are unable to come to a conclusion either way. Unfortunately, they don't suggest ways of testing these hypotheses. I suggets it may be a little premature to speculate too seriously about this single result, interesting though it is. Future work on the geology of the region and further systematic research on the silktail and the remainder of the avifauna of Melanesia may reveal other potential explanations.

Irestedt M., Ruchs J., Jonsson K., Ohlson J. I., Pasquet E., Ericson P. G. P. (2008) The systematic affinity of the enigmatic Lamprolia victoriae (Aves: Passeriformes) - An example of avian dispersal between New Guinea and Fiji over Miocene intermittent land bridges? Molecular Phylogenetics and Evolution 48: 1218-1222

Picture courtesy of Birdlife International

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