Evolutionary Ecology

, Volume 24, Issue 4, pp 731–748

Interactions between sexual and natural selection on the evolution of a plumage badge

Authors

    • Smithsonian Migratory Bird CenterNational Zoological Park
    • Department of Biological SciencesVirginia Tech
    • School of Biology & EcologyUniversity of Maine
  • Russell Greenberg
    • Smithsonian Migratory Bird CenterNational Zoological Park
  • Irene A. Liu
    • Department of BiologyUniversity of Maryland
  • Joshua M. Felch
    • Department of Fisheries & Wildlife SciencesVirginia Tech
  • Jeffrey R. Walters
    • Department of Biological SciencesVirginia Tech
Original paper

DOI: 10.1007/s10682-009-9330-4

Cite this article as:
Olsen, B.J., Greenberg, R., Liu, I.A. et al. Evol Ecol (2010) 24: 731. doi:10.1007/s10682-009-9330-4

Abstract

The evolutionary stability of signals varies due to interactions between sexual and natural selection. A tidal-marsh sparrow, Melospiza georgiana nigrescens, possesses darker pigmentation than an inland-marsh sparrow, M. g. georgiana. Studies of feather-degrading bacteria and convergent evolution among salt-marsh vertebrates suggest this dark coloration is due to environmental selection. Sexually dichromatic swamp sparrow crowns, however, may be additionally under sexual selection. We investigated ties between two plumage patches (rusty cap and black forehead) and two behaviors (male-male aggression and parental care) in the coastal and inland subspecies to test the effect of sexual versus natural selection on badge evolution. Across both subspecies the extent of rusty feathers in the cap patch was correlated positively with parental care and negatively with aggression, and the extent of black feathers in the forehead patch was correlated positively with aggression. Males with larger forehead patches produced more offspring along the coast, while males with larger cap patches did so inland. The date of the first nesting attempt for both subspecies correlated with cap patch extent, suggesting a similar role for female choice. Natural selection likely accounts for darker coastal females. Coastal male head color, however, is darker due to increased selection for larger forehead patches via intrasexual competition, yet it remains largely rusty due to female choice for larger cap patches. Increased sexual dichromatism among coastal plain swamp sparrows thus provides a clear example of the interplay between sexual and natural selection in subspecies divergence.

Keywords

Sexual dimorphismDichromatismMelospiza georgiana nigrescensMating systemSpeciationSignals

Copyright information

© Springer Science+Business Media B.V. 2009