Morph-dependent resource acquisition and fitness in a polymorphic bird

• Published in: Evolutionary ecology Vol. 27; no. 6; pp. 1189 - 1198
• Main Authors: Brazill-Boast, James, Griffith, Simon C., Pryke, Sarah R.
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.11.2013; Springer; Springer Nature B.V
• Subjects: Animal Ecology; Animal reproduction; Biomedical and Life Sciences; Birds; Conspecifics; Ecology; Evolutionary Biology; Genetic aspects; Genetic diversity; Genetic polymorphisms; Genotype & phenotype; Life Sciences; Males; Original Paper; Plant Sciences; Polymorphism; Reproduction; Colour polymorphism; Gouldian finch; Male competition; Alternative reproductive strategies
• ISSN: 0269-7653; 1573-8477
• DOI: 10.1007/s10682-013-9651-1

Understanding genetic colour polymorphism has proved a major challenge, both in terms of the underlying genetic mechanisms and the evolutionarily forces maintaining such genetic variation. In this context, genetic differences in aggression or competitive-related traits may covary with the expression of alternative phenotypes, and affect the evolutionary stability and maintenance of colour polymorphisms. Genetic red and black head-colour morphs of the Gouldian finch ( Erythrura gouldiae ) co-occur in temporally and geographically stable frequencies in sympatric populations. Gouldian finches are obligate cavity-nesters with highly specific preferences for nest-site morphometry that directly affect reproductive success. Because intra- and interspecific competition for high quality nest-sites is prevalent, and fitness is directly related to nest-site quality, we investigated the relative access (and consequences for reproductive success) of alternative morphs to this critical limiting resource in the wild. Red males defended higher quality nest-sites, and overcame greater levels of nest-site competition against conspecifics and superior heterospecific competitors than black males. Red-headed males also produced more fledglings (especially with red-headed females) than black-headed males, independent of nest-site quality. Finally, the independent (positive) effect of nest-site quality on reproductive success was confirmed. Such competitive asymmetries are important to relative selection among coexisting morphs, and are likely to contribute to the maintenance of alternative sympatric colour-morphs in wild populations.