Alectroenas G.R. Gray, 1840

Hume, Julian Pender, 2011, 3124, Zootaxa 3124, pp. 1-62 : 28

Genus Alectroenas G.R. Gray, 1840 .

Alectroenas G.R. Gray, 1840, p.58 . Type, by original designation, A. franciae (Lath.) = Columba franciae Gmelin = Columba nitidissima Scopoli.

Etymology: From Greek a lektruon, the domestic cock, and oinas, a dove, in reference to the bare red face and coxcomb of the Mauritius blue pigeon.

Diagnosis: Alectroenas is distinguished from other Mascarene columbids by the following characters: cranium, in lateral aspect, os lacrimale extremely wide, fonticulus orbitocranialis smaller than foramen n. optici, but both indistinct, in ventral aspect, rounded and distinct condylus occipitalis, indistinct medial groove running anterioposteriorly across ala parasphenoidalis complex; sternum, constriction of sternum between incisura lateralis; humerus, caput humeri proximodistally elevated, comparatively flattened; facies bicipitalis less medially projecting; tuberculum dorsale narrow and elongate, with slight protrusion, and orientated along axis of the bone; distally more mediolaterally elongate; crista bicipitalis forming a rounded right angle to shaft and with shallow incisura capitis; processus supracondylaris dorsalis situated more proximad to distal end; on cranial surface, fossa m. brachialis wide; condylus ventralis globular-shaped; tuberculum supracondylare ventrale indistinct; femur, proportionately robust with distinct crista trochanteris; tibiotarsus, more robust in shaft and overall shorter, but proportionately gracile at proximal and distal ends; tarsometatarsus, distinct crista medialis hypotarsi directed laterally displacing cotyla lateralis dorsally. Osteologically, the species of Alectroenas have a long tibiotarsus and a short tarsometatarsus; in leg to wing length ratios, the wing elements are proportionately long.

Compared with other columbids of similar size, the species of Alectroenas are medium to large stocky pigeons with comparatively short wings and tails, the feathers around the head and neck forming distinct hackles that can be raised and lowered at will.

Remarks: The blue pigeons have distant affinities with Indo-Pacific fruit pigeons, in particular the New Caledonian Cloven-feathered Dove Drepanoptila holosericea , with Ptilinopus representing the ancestral group ( Shapiro et al. 2002; Pereira et al. 2007). The populations of Alectroenas , which are all allopatric, have been regarded as a superspecies ( Greenway 1967; Goodwin 1983; Gibbs et al. 2001). They may represent relics of an ancient radiation from SE Asia, having evolved their distinctive characters on islands in the Indian Ocean. The distribution of Alectroenas throughout the south-west Indian Ocean was presumably achieved through island-hopping during sea level low stands, reaching the Mascarenes possibly via the Seychelles, using now submerged islands and archipelagos along the mid Indian Ocean ridges ( Cheke & Hume 2008; Warren et al. 2010).