Diversification and community assembly of the world’s largest tropical island

Aim: The species diversity and endemism of tropical biotas are major contributors toglobal biodiversity, but the factors underlying the formation of these systems remainpoorly understood.Location: The world's largest tropical island, New Guinea.Time period: Miocene to present.Major taxa studied: Passerine birds.Methods: We first generated a species- level phylogeny of all native breeding passer-ine birds to analyse spatial and elevational patterns of species richness, species ageand phylogenetic diversity. Second, we used an existing dataset on bill morphology toanalyse spatial and elevational patterns of functional diversity.Results: The youngest New Guinean species are principally distributed in the low-lands and outlying mountain ranges, with the lowlands also maintaining the majorityof non-endemic species. In contrast, many species occurring in the central mountainrange are phylogenetically distinct, range-restricted, endemic lineages. Centres ofaccumulation for the oldest species are in montane forest, with these taxa havingevolved unique bill forms in comparison to the remaining New Guinean species. Forthe morphological generalists, attaining a highland distribution does not necessarilyrepresent the end to dispersal and diversification, because a number of new specieshave formed in the outlying mountain ranges, following recent colonization from thecentral rangeMain conclusions: We conclude that a general model of tropical montane diversifica-tion is that lineages commonly colonize the lowlands, shifting their ranges upslopethrough time to become range-restricted montane forest endemics, attaining novelfunctional adaptations to these environments.