The phylogenetic distribution of ultraviolet sensitivity in birds

Anders Ödeen,Olle Håstad

doi:10.1186/1471-2148-13-36

Anders Ödeen, Olle Håstad

Open Access

https://doi.org/10.1186/1471-2148-13-36

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Abstract

BackgroundColour vision in birds can be categorized into two classes, the ultraviolet (UVS) and violet sensitive (VS). Their phylogenetic distributions have traditionally been regarded as highly conserved. However, the complicated nature of acquiring spectral sensitivities from cone photoreceptors meant that until recently, only a few species had actually been studied. Whether birds are UVS or VS can nowadays be inferred from a wide range of species via genomic sequencing of the UV/violet SWS1 cone opsin gene.ResultsWe present genomic sequencing results of the SWS1 gene from 21 avian orders. Amino acid residues signifying UV sensitivity are found in the two most important spectral tuning sites 86 and 90 of Pteroclidiformes and Coraciiformes, in addition to the major clades, Palaeognathae, Charadriiformes, Trogoniformes, Psittaciformes and Passeriformes, where they where previously known to occur. We confirm that the presumed UVS-conferring amino acid combination F86, C90 and M93 is common to Palaeognathae and unique to this clade, despite available spectrometric evidence showing the ostrich retina to be VS.ConclusionsBy mapping our results together with data from previous studies on a molecular phylogeny we show that avian colour vision shifted between VS and UVS at least 14 times. Single nucleotide substitutions can explain all these shifts. The common ancestor of birds most likely had a VS phenotype. However, the ancestral state of the avian SWS1 opsin’s spectral tuning sites cannot be resolved, since the Palaeognathae are F86, C90 while the Neognathae are ancestrally S86, S90. The phylogenetic distribution of UVS and VS colour vision in birds is so complex that inferences of spectral sensitivities from closely related taxa should be used with caution.

Highlights

Colour vision in birds can be categorized into two classes, the ultraviolet (UVS) and violet sensitive (VS)
Cycle sequencing produced 50–160 bp long overlapping sequences of the short-wavelength sensitive type 1 pigment (SWS1) opsin gene from 40 species belonging to 29 families and 21 orders, 11 families and six orders being new to this study
We found residues of C90 in the Palaeognathae species ostrich Strutio camelus, southern cassowary Casuarius casuarius and emu Dromaius novaehollandiae, as well as in the two Cacatuidae and three Psittacidae species, confirming that C90 is common to Psittaciformes (New Zealand parrots, cockatoos and true parrots)

Summary

Introduction

Colour vision in birds can be categorized into two classes, the ultraviolet (UVS) and violet sensitive (VS). Their phylogenetic distributions have traditionally been regarded as highly conserved. Spectral tuning in all but one class of pigment is achieved by replacement of one of the chromophores for the other [1] (11-cis-retinal blueshifts compared to 11-cis-3,4-dehydroretinal [2,3]), In recent years, portable spectrophotometers and the development of vision physiological models have made it possible to quantify how colour signals are perceived by the natural observer, a bird for example, given that visual physiological data for the species in question are known. Since in-depth physiological studies on the visual system have been limited to a few species, researchers have had to rely on a widely accepted assumption of strong phylogenetic inertia in the evolution of colour vision systems, using data from related species, in which the information is available [12]

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