Variable visual habitats may influence the spread of colourful plumage across an avian hybrid zone

Abstract

Several studies have shown that hybridization can be a creative process by acting as a conduit for the spread of adaptive traits between species, but few provide the mechanism that favours this spread. In the hybrid zone between the golden‐ (Manacus vitellinus) and white‐collared (Manacus candei) manakins, sexual selection drives the introgression of golden/yellow plumage into the white species; however, the mechanism for the yellow male's mating advantage and the reasons why yellow plumage has not swept further into the white species remain mostly speculative. We quantified the colour properties of male plumage, the background and the ambient light at the hybrid zone, and allopatric golden and white populations. As measured by the perceived difference in colour between plumage and background, we found that yellow plumage appears more conspicuous than white plumage in the hybrid zone and allopatric golden‐collar habitats, whereas white plumage appears more conspicuous than yellow plumage in the allopatric white‐collared habitat. These results suggest a mechanism for the unidirectional spread of yellow plumage across the hybrid zone but slowed movement beyond it.

Experimental evidence that extra-pair mating drives asymmetrical introgression of a sexual trait

“…sensory drive [44]). This is the mechanism invoked to explain the asymmetrical introgression of golden plumage in the hybrid zone between golden-and white-collared manakins, where golden plumage is more visually conspicuous than white [14].…”

“…One of the best examples comes from golden-and white-collared manakins (Manacus spp. ), where the asymmetrical introgression of a secondary sexual trait, male throat plumage colour [11,12], has been driven by sexual selection [13,14]. However, the extent to which this phenomenon is more widespread is unclear, and the underlying mechanisms driving such patterns are seldom investigated (but see [15,16]).…”

Diurnal lighting patterns and habitat alter opsin expression and colour preferences in a killifish

“…colour) contrasts for species whose visual properties differ from that of humans [48]. These models have been applied to studies of both mating [46,49] and foraging preferences [50] and have been used to estimate the effects of altering the lighting environment [44,51] and the visual system properties of the receivers [52,53] on colour perception. The application of these models to the L. goodei system may resolve both (i) the pattern of blue males being more abundant in tannin-stained waters, and (ii) the maintenance of multiple colour morphs within populations.…”

Evolution of opsin expression in birds driven by sexual selection and habitat

“…The null hypothesis is that colours evolve to exploit an invariant receiver's sensory system [2,3]. For example, colours can appear relatively conspicuous or cryptic against different backgrounds [4,5] or, as initially suggested by Darwin [6], novelty per se may be attractive to females. In one alternative hypothesis, colour perception and colourful displays co-evolve even if populations occupy similar environments.…”