Ecological and evolutionary diversification in the Australo-Papuan scrubwrens (Sericornis) and mouse-warblers (Crateroscelis), with a revision of the subfamily Sericornithinae (Aves: Passeriformes: Acanthizidae)

Abstract

Understanding how the complex geotectonic and climatic history of the Australo-Papuan region has promoted the ecological and evolutionary diversification of its avifauna remains a challenge. Outstanding questions relate to the nature and timing of biogeographical connections between Australia and the emerging island of New Guinea and the mechanisms by which distinctive altitudinal replacement sequences have evolved amongst congeneric species in montane New Guinea. Here, we combine analyses of phylogenetic and eco-morphological data to investigate ecological and evolutionary patterns of diversification in the largely mesic-adapted Australo-Papuan scrubwrens (Sericornis) and mouse-warblers (Crateroscelis). We find evidence of ecological convergence and present a revised taxonomic and systematic treatment of the subfamily integrating information from new (ND2) and existing molecular phylogenetic reconstructions. Biogeographical connections indicate at least three phases of faunal interchange between Australia and New Guinea commencing in the mid to late Miocene. We also find little support for the proposed time dependency of ecological sorting mechanisms linked to divergence in foraging niche amongst altitudinal replacements. Instead, physiological adaptations to hypoxia and increased thermal efficiency at higher altitudes may better account for observed patterns of diversification in montane New Guinea. Indirect support for this hypothesis is derived from molecular clock calibrations that indicate a pulse of diversification across the Miocene-Pliocene boundary coincident with a phase of rapid mountain uplift. Simple ecological and climatic models appear inadequate for explaining observed patterns and mechanisms of diversification in the New Guinean montane avifauna. Further insights will require multidisciplinary research integrating geotectonic, palaeoclimatic, genetic, ecological and physiological approaches.