title: Blue reflectance in tarantulas is evolutionarily conserved despite nanostructural diversity.
abstract: Slight shifts in arrangement within biological photonic nanostructures can produce large color differences, and sexual selection often leads to high color diversity in clades with structural colors. We use phylogenetic reconstruction, electron microscopy, spectrophotometry, and optical modeling to show an opposing pattern of nanostructural diversification accompanied by unusual conservation of blue color in tarantulas (Araneae: Theraphosidae). In contrast to other clades, blue coloration in phylogenetically distant tarantulas peaks within a narrow 20-nm region around 450 nm. Both quasi-ordered and multilayer nanostructures found in different tarantulas produce this blue color. Thus, even within monophyletic lineages, tarantulas have evolved strikingly similar blue coloration through divergent mechanisms. The poor color perception and lack of conspicuous display during courtship of tarantulas argue that these colors are not sexually selected. Therefore, our data contrast with sexual selection that typically produces a diverse array of colors with a single structural mechanism by showing that natural selection on structural color in tarantulas resulted in convergence on similar color through diverse structural mechanisms.
authors.affiliation: Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325-3908, USA.
authors.forename: Bor-Kai
authors.identifier: 0000-0001-9657-3484
authors.initials: BK
authors.lastname: Hsiung
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, La Jolla, CA 92093, USA.
authors.forename: Dimitri D
authors.identifier: 0000-0002-6496-9297
authors.initials: DD
authors.lastname: Deheyn
authors.affiliation: Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325-3908, USA.
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Shawkey
authors.affiliation: Department of Biology and Integrated Bioscience Program, The University of Akron, Akron, OH 44325-3908, USA.
authors.forename: Todd A
authors.initials: TA
authors.lastname: Blackledge
keywords: Natural selection; Sexual selection; Structural color; multilayer; non-iridescence; quasi-order