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

Abstract

Aim:The species diversity and endemism of tropical biotas are major contributors to global biodiversity, but the factors underlying the formation of these systems remain poorly 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 passerine birds to analyse spatial and elevational patterns of species richness, species age and phylogenetic diversity. Second, we used an existing dataset on bill morphology to analyse spatial and elevational patterns of functional diversity. Results:The youngest New Guinean species are principally distributed in the lowlands and outlying mountain ranges, with the lowlands also maintaining the majority of non-endemic species. In contrast, many species occurring in the central mountain range are phylogenetically distinct, range-restricted, endemic lineages. Centres of accumulation for the oldest species are in montane forest, with these taxa having evolved unique bill forms in comparison to the remaining New Guinean species. For the morphological generalists, attaining a highland distribution does not necessarily represent the end to dispersal and diversification, because a number of new species have formed in the outlying mountain ranges, following recent colonization from the central range.

Species-specific dynamics may cause deviations from general biogeographical predictions – evidence from a population genomics study of a New Guinean endemic passerine bird family (Melampittidae)

“…Alternatively, extensive lowland valleys can also act as barriers to geneflow between populations adapted to high elevations. Lowland environments may be unsuitable for such mountain-adapted individuals, which over time become isolated on a series of mountaintops or "sky islands" [10,11] as known from some groups of birds, lizards and plants [12][13][14][15][16]. Related to this is the observation that older taxa are often found at higher elevations, while young lineages that are generally widespread, good dispersers and show little differentiation inhabit the lowlands (e.g.…”

“…Related to this is the observation that older taxa are often found at higher elevations, while young lineages that are generally widespread, good dispersers and show little differentiation inhabit the lowlands (e.g. [16][17][18][19]. Such observations (mostly from island systems) have led to the formulation of the concept of taxon cycles, in which taxa pass through phases of expansions and contractions.…”

“…Recent work on the New Guinean avifauna has provided empirical evidence in favour of species originating in the lowlands from where they move into the highlands over time and become relictual specialists [16,22,23], although some colonisation from mountaintop to mountaintop has also been shown to occur [15]. In addition, recent Pleistocene speciation events on New Guinea are mainly the result of changes in habitat distributions due to climate fluctuations, as this has caused species with continuous distributions to become geographically fragmented [24][25][26].…”

A guide to avian museomics: Insights gained from resequencing hundreds of avian study skins

“…In this paper, we provide an overview of our workflow and discuss the challenges associated with generating genome‐scale data sets from historical avian specimens. The paper draws on our extensive experience in obtaining genetic data from avian study skins for more than 15 years (e.g., Irestedt et al, 2006; Jonsson et al, 2007; Jonsson et al, 2012), and in particular our extensive recent work with the resequencing of entire genomes from avian study skins (see, e.g., Ericson et al, 2021; Ericson et al, 2017; Ericson et al, 2019; Ernst et al, 2022; Irestedt et al, 2019; Jonsson et al, 2019; Kennedy et al, 2022). It is not our aim to review the entire field of museomics, as there are numerous laboratory and analytical methods described in the literature both for DNA extraction (e.g., Tsai et al, 2020) and for genome library preparation from museum samples (Carøe et al, 2018; Kapp et al, 2021; Meyer & Kircher, 2010); each has its own benefits and potential drawbacks.…”

The formation of the Indo-Pacific montane avifauna

“…Wilson (1959, 1961), who argued that montane species form via ‘taxon cycles’ whereby dispersive lowland radiations gradually contract into the highlands to form endemic species restricted to single islands. These ideas are hard to reconcile, and molecular studies have found evidence of both processes (Jønsson et al, 2014, 2017; Pepke et al, 2019; Cadena & Céspedes, 2020, Kennedy et al, 2022), even within a single mountain community (Merckx et al, 2015).…”