Ocean flycatcher paradise

A phylogenetic analysis of the Indian Ocean paradise flycatchers has revealed that they probably consist of six rather than the currently recognised three species.

The forms of these ostentatiously attractive flycatchers are quite similar in having generally long-tailed males, and plumage composed of blocks of rufous wings, grey-brown underparts, black heads and sometimes white wing patches. There is sexual dimorphism, with most species having short-tailed slightly duller females, and some taxa have white or black phase birds; a few forms are all-black. It may be that these variations and the presence of phases reflect population bottlenecks with inbreeding or 'founder effects' in the recent past.

Using four mitochondrial and two nuclear gene sequences, phylogenetic analyses were performed on museum specimens of all species and subspecies of Terpsiphone flycatcher known from the Indian Ocean region. Only three species – Malagasy, Seychelles and Mascarene Paradise Flycatchers – are currently recognised from the region, but the forms fall into five well-defined clades – that is, groupings of each others' closest relatives.

The authors confirmed the divergence of the two traditional species, but found that all six taxa detected in their analysis should be treated as separate Evolutionary Significant Units (ESUs), sometimes colloquially termed 'conservation species'. With three of the clades having genetic distances ranging between 3.6 and 3.77 per cent, these at least would be considered 'good' species by birders and most biologists visiting the region.

The ESUs defined by the paper are:

• T corvina (Seychelles Paradise Flycatcher)
• T (mutata) vulpina (including the subspecies voeltzkowiana [from Anjouan]) (Comoros Paradise Flycatcher)
• T (mutata) mutata (includingthe subspecies singetra [from north, west and south Madagascar], pretiosa [from Mayotte]) (Malagasy Paradise Flycatcher – nominate is the eastern subspecies)
• T (mutata) comorensis (Grand Comore Paradise Flycatcher)
• T (bourbonnensis) bourbonnensis (Réunion Paradise Flycatcher)
• T (bourbonnensis) desolata (Mauritius Paradise Flycatcher)

Interestingly, Sao Tome Paradise Flycatcher T atrochalybeia – from the Gulf of Guinea on the Atlantic side of Africa – is closely allied to the Seychelles form T corvina, but this probably reflects a common secondary origin in the continental African T viridis or Bates's T batesi Paradise Flycatchers, sister species from West Africa. The two subspecies of South Asian T paradisi included in the analysis are closer to the Macaronesian bourbonnensis forms, reflecting probable colonisation from the north by these ancestral, basal forms. Both colonisations occurred within the last two million years, accounting for the close similarities of the taxa, though the root origin of the genus appears to be Asia.

The authors recommend splitting for taxonomic and conservation purposes.

Reference
Bristol, R M, Fabre, P-H, Irestedt, M, Jønsson, K A, Shah, N J, Tatayah, V, Warren, B H, and Groombridge, J J. 2013. Molecular phylogeny of the Indian Ocean Terpsiphone paradise flycatchers: undetected evolutionary diversity revealed amongst island populations. Molecular and Phylogenetic Evolution (in press). http://dx.doi.org/10.1016/j.ympev.2013.01.019