The evolutionary history of cockatoos (Aves: Psittaciformes: Cacatuidae)

Abstract

Cockatoos are the distinctive family Cacatuidae, a major lineage of the order of parrots (Psittaciformes)and distributed throughout the Australasian region of the world. However, the evolutionary history ofcockatoos is not well understood. We investigated the phylogeny of cockatoos based on three mitochondrialand three nuclear DNA genes obtained from 16 of 21 species of Cacatuidae. In addition, five novelmitochondrial genomes were used to estimate time of divergence and our estimates indicate Cacatuidaediverged from Psittacidae approximately 40.7 million years ago (95% CI 51.6–30.3 Ma) during the Eocene.Our data shows Cacatuidae began to diversify approximately 27.9 Ma (95% CI 38.1–18.3 Ma) during theOligocene. The early to middle Miocene (20–10 Ma) was a significant period in the evolution of modernAustralian environments and vegetation, in which a transformation from mainly mesic to xeric habitats(e.g., fire-adapted sclerophyll vegetation and grasslands) occurred. We hypothesize that this environmentaltransformation was a driving force behind the diversification of cockatoos. A detailed multi-locusmolecular phylogeny enabled us to resolve the phylogenetic placements of the Palm Cockatoo(Probosciger aterrimus), Galah (Eolophus roseicapillus), Gang-gang Cockatoo (Callocephalon fimbriatum)and Cockatiel (Nymphicus hollandicus), which have historically been difficult to place within Cacatuidae.When the molecular evidence is analysed in concert with morphology, it is clear that many of thecockatoo species’ diagnostic phenotypic traits such as plumage colour, body size, wing shape and billmorphology have evolved in parallel or convergently across lineages.