Key ornamental innovations facilitate diversification in an avian radiation

Abstract

Patterns of biodiversity are often explained by ecological processes, where traits that promote novel ways of interacting with the environment (key innovations) play a fundamental role in promoting diversification. However, sexual selection and social competition can also promote diversification through rapid evolution of ornamental traits. Because selection can operate only on existing variation, the tendency of ornamental traits to constrain or enable the production of novel phenotypes is a crucial but often overlooked aspect of diversification. Starlings are a speciose group characterized by diverse iridescent colors produced by nanometer-scale arrays of melanin-containing organelles (melanosomes) that play a central role in sexual selection and social competition. We show that evolutionary lability of these colors is associated with both morphological and lineage diversification in African starlings. The solid rod-like melanosome morphology has evolved in a directional manner into three more optically complex forms that can produce a broader range of colors than the ancestral form, resulting in (i) faster color evolution, (ii) the occupation of novel, previously unreachable regions of colorspace, and ultimately (iii) accelerated lineage diversification. As in adaptive radiations, key innovations in ornament production can provide high phenotypic trait variability, leading to dramatic effects on the tempo and mode of diversification.biophotonics | macroevolution | phylogenetics | structural color | Sturnidae

Sparkling feather reflections of a bird-of-paradise explained by finite-difference time-domain modeling

“…1, 2). A comparative investigation of the highly specialized feathers and the visual system will elucidate the evolution of avian plumage as well as the importance of key variations in barbule morphology (37) and feather color in connection to the visual ecology of avian photoreceptors (23,24).…”

Characterization and Biomimcry of Avian Nanostructured Tissues

“…We calculated contrast gloss as the ratio of summed specular to summed diffuse reflectance (Hunter's contrast gloss: Hunter, 1937;Maia, 2011;Igic et al 2015). All spectral analyses were done in R using the pavo package (Maia et al, 2013).…”

“…Understanding the mechanisms underlying production and maintenance of feather colors is critical to understanding their function (Prum, 2006;Shawkey, Morehouse & Vukusic, 2009;Wilts et al, 2014), the constraints on their production McGraw, 2006;Galvan & Alonso-Alvarez, 2008), and their evolution (Stoddard & Prum, 2011, Maia, Rubenstein & Shawkey, 2013. Traditionally, feather colors have been classified as either pigment-based (produced by selective absorption of certain wavelengths of light by molecules, mainly melanins and carotenoids) or structural (produced by differential scattering and interference as light interacts with materials of varying refractive indices; Prum, 2006).…”

Neutral Theory Overestimates Extinction Times in Nonhuman Primates

“…Specific explanations for nonlinear or neutral diversification patterns will require further work to investigate the tempo of diversification in relation to historical characteristics and the ecological features of each taxon (Baker et al 2014;Eiserhardt et al 2013;FitzJohn 2012;Magnuson-Ford and Otto 2012;Maia et al 2013). An evaluation of interactions between primates and plants found that diversification rates of mutualistic species are higher than those of antagonistic species (Gómez and Verdú 2012).…”