Dispersal has inhibited avian diversification in Australasian archipelagoes

Abstract

Different models of speciation predict contrasting patterns in the relationship between the dispersal ability of lineages and their diversification rates. This relationship is expected to be negative in isolation-limited models and positive in founder-event models. In addition, the combination of negative and positive effects of dispersal on speciation can result in higher diversification rates at intermediate levels of dispersal ability. Using molecular phylogenies to estimate diversification rates, and wing morphology to estimate dispersal ability, we analysed the influence of dispersal on diversification in the avifauna of Australasian archipelagoes. Contrary to expectations given the fragmented nature of island systems, the relationship between dispersal ability and diversification rate was monotonically negative. While multiple mechanisms could generate this pattern, they all share a phase of range expansion that is decoupled from speciation.

How do seemingly non-vagile clades accomplish trans-marine dispersal? Trait and dispersal evolution in the landfowl (Aves: Galliformes)

“…Under the taxon cycle hypothesis, larger body sizes of Margaroperdix and Anurophasis would be interpreted as character displacement to avoid competition, and loss of dispersal capability as an adaptation to reduce metabolic cost of large flight musclessimultaneously reducing dispersal capability [63,65,66]. Maintenance of flight muscle mass needed for long dispersal flights is energetically demanding [66], and insular bird populations tend to evolve towards reduced dispersal if there is not strong connectivity with nearby populations [1,50,67]. In extreme cases, this selection pressure can lead to complete flightlessness [68].…”

“…Wings with high aspect ratio/high HWI are longer, narrower and produce greater lift than wings with low aspect ratio/low HWI. HWI correlates strongly with dispersal capabilities [49][50][51]. We calculated mean HWI for phasianoids and outgroups based on measurements from traditional museum skins with the wings prepared folded on the body.…”

Bird assemblage vulnerability depends on the diversity and biogeographic histories of islands

“…in which WL is the standard measure of wing length, and SL is a measure of the distance from the carpal joint to the tip of the first secondary feather (18,40). For each species, HWI was based on the measurement of three adult male specimens, when available, at the American Museum of Natural History (AMNH).…”

“…Climate-driven sea level change is an example of a key historical biogeographic process that is of particular relevance in island systems. Changes in island connectivity as a result of sea level fluctuation have been invoked to explain relationships between fundamental evolutionary processes (e.g., the relationship between dispersal and diversification rates) (18) and have been related to key evolutionary outcomes (e.g., species richness and endemism) (19). In the Solomon Archipelago, throughout the Pleistocene, fluctuations in sea level have connected and isolated some islands repeatedly, whereas others have remained isolated throughout their histories; these historical connections are clearly evident in the distributions of diversity in the Archipelago, with taxa typically endemic to islands that formed single landmasses at the Last Glacial Maximum (LGM) (20).…”

Phylogeography of a good Caribbean disperser: Argiope argentata (Araneae, Araneidae) and a new ‘cryptic’ species from Cuba

“…Regardless, all the Greater Antilles islands and most of the minor Antilles have been isolated for the last several million years (Ali 2012; Heinicke et al 2007; Iturralde-Vinent and MacPhee 1999; Iturralde-Vinent 2006). Thus the processes of divergence and diversification among islands due to lack of gene-flow can be expected to be ongoing in all but the best dispersing organisms for which stretches of ocean do not present formidable barriers—one prediction of the (IDM)intermediate dispersal model (Agnarsson et al 2014; Claramunt et al 2012; Weeks and Claramunt 2014). Such organisms are typically flying animals, or plants with salt-tolerant floating seeds, that are widespread but species depauperate (Weeks and Claramunt 2014).…”