Experimental test of selection against hybridization as a driver of avian signal divergence

• Published in: Journal of evolutionary biology Vol. 35; no. 8; pp. 1087 - 1098
• Main Authors: Kenyon, Haley L., Martin, Paul R.
• Format: Journal Article
• Language: English
• Published: Oxford Blackwell Publishing Ltd 01.08.2022
• Subjects: Biodiversity; Birds; character displacement; Color; colour divergence; Congeners; Conspecifics; Copulation; Divergence; female choice; Females; Field tests; Hybridization; Mate selection; Poecile; signal evolution; Species; species recognition; Sympatric populations; Sympatry; Three dimensional models; Three dimensional printing
• ISSN: 1010-061X; 1420-9101
• DOI: 10.1111/jeb.14058

Signal divergence may be pivotal in the generation and maintenance of new biodiversity by allowing closely related species to avoid some costs of co‐occurrence. In birds, closely related, sympatric species are more divergent in their colour patterns than those that live apart, but the selective pressures driving this pattern remain unclear. Traditionally, signal divergence among sympatric species is thought to result from selection against hybridization, but broad evidence is lacking. Here, we conducted field experiments on naïve birds using spectrometer‐matched, painted 3D‐printed models to test whether selection against hybridization drives colour pattern divergence in the genus Poecile. To address selection for male colour pattern divergence without the influence of learning or the evolution of female discrimination in sympatry, we simulated secondary contact between Poecile species, and conducted mate choice experiments on naïve, allopatric females. We found that female black‐capped chickadees (Poecile atricapillus) are equally likely to perform copulation solicitation displays to sympatric and allopatric heterospecific congeners when they are paired with conspecifics, but exhibit a strong preference for less divergent males when presented with paired heterospecific congeners. These results suggest that increased colour pattern divergence among sympatric species can reduce the likelihood of mixed mating in some contexts, and therefore should be favoured by selection against hybridization. We conducted a field experiment using colour‐matched, 3D printed models to test whether selection against hybridization favours colour pattern divergence among closely related, sympatric species of birds. Our results suggest that colour pattern differences can reduce mixed mating attempts between closely related, sympatric species, and may therefore be favoured due to selection against hybridization. (Illustrations reproduced by permission of Lynx Edicions).