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.

From earthquakes to island area: multi‐scale effects upon local diversity

“…Here, we propose hypotheses that consider the impact of geological and climatic histories on diversity. The rapid recent formation of Wallacea and Sahul's environmental gradients could have promoted diversification and resulted in greater local diversity (Toussaint et al 2014, Rowe et al 2019, Kennedy et al 2022, McCullough et al 2022, Roycroft et al 2022, Struebig et al 2022). More likely, the longer residence time of terrestrial areas in Sunda may have resulted in the build‐up of greater regional diversity, increasing the possible number of species able to coexist locally (de Bruyn et al 2014, O'Connell et al 2018).…”

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)

“…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].…”

Challenges in estimating species age from phylogenetic trees

“…More recently, several studies have used the length of terminal branches in time-calibrated phylogenies as a proxy for the age of extant species, an approximation that we hereafter refer to as "phylogenetic age" (Alzate et al, 2023;Davies et al, 2011;Gaston & Blackburn, 1997;Johnson et al, 2002;Pie & Caron, 2023;Sonne et al, 2022;Tanentzap et al, 2020;Verde Arregoitia et al, 2013). These phylogenetic ages have been used as the basis to test for links between species age and current extinction risks (Tanentzap et al, 2020;Verde Arregoitia et al, 2013) and to assess various correlations with evolutionary, biogeographical, and ecological patterns in living species (Alzate et al, 2023;Freer et al, 2022;Kennedy et al, 2022;Pie & Caron, 2023) While several studies have used phylogenetic age at face value for species age (e.g., Johnson et al 2002;Tanentzap et al 2020;Verde Arregoitia et al 2013), their potential deviation from the true species ages remains unclear. Specifically, we identify three nonmutually exclusive shortfalls that can lead to over-or underestimation of species ages.…”