Species limits and phylogenetic relationships in Corellas of the Cacatua pastinator complex

Abstract

Three species are strongly indicated in the Cacatua pastinator complex of Australia: the eastern long-billed tenuirostris, the western long-billed pastinator and the short-billed sanguinea. The latter is composed of five subspecies (three in Australia and two overseas). New information indicates that pastinator and sanguinea became sympatric in the northern wheatbelt of south-western Australia about 75 years ago through man's agricultural activities yet rarely, if ever, hybridize. Multivariate analyses revealed only one possible hybrid in 176 adult specimens from the overlap zone. Though the northern population of pastinator is morphometrically intermediate between the southern population of pastinator and that of sanguinea in the Pilbara, no support was found for the intermediacy having been caused by either an ancient-cline involving all three population or past introgression. A re-examination of character states in the complex indicates that pastinator and tenuirostris might not have independently acquired a long-tipped bill. If previous diagnoses of ancestral and derived character states are accepted, the most parsimonious sequence of events requires tenuirostris and pastinator to have evolved from a common long-billed ancestor. If a critical character in tenuirostris is reassessed as ancestral and if only progressive character state changes are permitted, a cladogram showing a convergence in bill length is obtained. However, if reversals are permitted, parsimoniously derived cladograms indicate other evolutionary possibilities. Genetic data are required for further eludication of phylogenetic relationships in the complex.