A NEW SPECIES OF RAIL FROM THE SOLOMON-ISLANDS AND CONVERGENT EVOLUTION OF INSULAR FLIGHTLESSNESS

Gallirallus rovianae is an extant new species of flightless or weak-flying rail from the Solomon islands in the southwest Pacific Ocean. Within the Solomon islands it is known from New Georgia and reported from four neighboring islands, all joined at Pleistocene times of low sea level. The new species belongs to the G. philippensis group (sensu Olson 1973a) and is most similar to the widespread G. philippensis and to G. owstoni (Guam) and next most similar to G. wakensis (Wake). It exemplifies the phenomenon of convergent evolution in two respects. First, a volant ancestor similar to G. philippensis has independently given rise to flightless or weak-flying derivatives on numerous oceanic islands, including G. rovianae, G. owstoni, G. wakensis, G. australis (New Zealand), and others. Emphasizing the ease with which rails evolve flightlessness on islands, I note 10 other groups of rails in which insular flightlessness has evolved repeatedly. Second, I suggest that the ancestral species had boldly patterned plumage similar to that of G. philippensis, and that insular reduction of bold patterning has proceeded independently in G. roviannae, G. owstoni, G. wakensis, and several other G. philippensis derivatives.