The influence of wing morphology upon the dispersal, geographical distributions and diversification of the Corvides (Aves; Passeriformes)

Abstract

New species are sometimes known to arise as a consequence of the dispersal and establishment of populations in new areas. It has nevertheless been difficult to demonstrate an empirical link between rates of dispersal and diversification, partly because dispersal abilities are challenging to quantify. Here, using wing morphology as a proxy for dispersal ability, we assess this relationship among the global radiation of corvoid birds. We found that species distributions are associated with wing shape. Widespread species (occurring on both islands and continents), and those that are migratory, exhibit wing morphologies better adapted to long-distance flight compared with sedentary continental or insular forms. Habitat preferences also strongly predict wing form, with species that occur in canopies and/or areas of sparse vegetation possessing dispersive morphologies. By contrast, we found no significant differences in diversification rates among either the migratory or habitat classifications, but species distributed in island settings diversify at higher rates than those found on continents. This latter finding may reflect the elevated dispersal capabilities of widespread taxa, facilitating the radiation of these lineages across insular areas. However, as the correlations between wing morphology and diversification rates were consistently weak throughout our dataset, this suggests that historical patterns of diversification are not particularly well reflected by present-day wing morphology.

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].…”

Global dynamics of dispersal and diversification among passerine birds

“…Evolutionary changes in breeding systems (the evolution of pair breeding) and wing morphology (the evolution of more projected wing tips/higher aspect-ratios), were correlated with geographic expansion and the increased diversification of passerine clades (Marki et al 2015, Kennedy et al 2016c; Fig. 1 sections 1-2 and 4).…”

“…1 sections 1-2 and 4). These patterns reflect the association of the aforementioned trait combinations with increased rates of lineage dispersal and diversification throughout island settings (Marki et al 2015, Kennedy et al 2016c). …”

“…My main focus was to assess variation in species diversity among subsets of species that (1) differ in the extent of their phylogenetic isolation, and hence current diversification rates (Kennedy et al 2014(Kennedy et al , 2016a, (2) differ in wing morphology (Kennedy et al 2016c), or (3) differ in breeding system (Marki et al 2015). These analyses aimed to assess both geographic variation in these diversity patterns, and to locate areas where different groups of species are under or over-represented given the overall richness gradients (e.g., contrasting the diversity patterns of the most phylogenetically isolated lineages with those of the overall clade).…”

“…These ranges were recorded at a resolution of 1° x 1° (c. 110 km x 110 km). Ecological (habitat preferences, migratory behaviour), life-history (breeding systems) and further distributional information (presence on islands and continents) were compiled from published literature (see Marki et al 2015 andKennedy et al 2016c for further information). Finally, measurements of primary and secondary wing length were taken for 4,344 museum study skins representing 782 of the 789 species of Corvides recognized by the IOC v.2.7 (Gill and Donsker 2010).…”