Evol Ecol Res 9: 905-920 (2007)     Full PDF if your library subscribes.

Dynamics of multiple sexual signals in relation to climatic conditions

Gergely Hegyi,¹* János Török,¹ László Zsolt Garamszegi,² Balázs Rosivall,¹ Eszter Szöllősi¹ and Rita Hargitai¹

¹Behavioural Ecology Group, Department of Systematic Zoology and Ecology, Eötvös Loránd University, Pázmány Péter sétány 1/C, H-1117 Budapest, Hungary and  ²Department of Biology, Universiteit Antwerpen, Campus Drie Eiken, Universiteitsplein 1, 2610 Wilrijk, Belgium

Author to whom all correspondence should be addressed.
e-mail: everest@ludens.elte.hu

ABSTRACT

Question: Can trait-specific phenotypic plasticity in response to annual environmental variation lead to changes in the strength of sexual selection through the relative expression of sexual ornaments at the population level?

Data description: We recorded breeding dates and the sizes of white forehead and wing patches of male collared flycatchers (Ficedula albicollis) from 1998 to 2005 in a nestbox-breeding population in the Pilis Mountains, Hungary. As environmental predictors, we used the North Atlantic Oscillation (NAO) index and local weather data, classified as direct or indirect effects relative to the moult of the given ornament.

Search method: First, we used general linear mixed models to assess environmental effects on the within-individual changes and absolute yearly sizes of forehead and wing patches. We then used similar models to determine whether the relative sizes of the two plumage traits at the population level varied among years. Finally, we used multiple regressions to establish if the relative yearly expression of an ornament affected standardized sexual selection gradients on this ornament in the given year.

Conclusions: Within-individual changes in forehead and wing patch size were predicted by the climate of their moulting season (winter and summer, respectively). There was also an indirect effect of previous winter climate on changes in wing patch size. Environmental effects on the absolute expression of ornaments at the population level followed the within-individual patterns. The relative population-level expression of forehead and wing patches fluctuated significantly among years. Sexual selection on a given ornament increased with its relative expression in that year.

Keywords: collared flycatcher, condition-dependence, Ficedula albicollis, North Atlantic Oscillation, phenotypic plasticity, plumage ornament, sexual selection.

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