Climatic and Temporal Effects on the Expression of Secondary Sexual Characters: Genetic and Environmental Components

Abstract

Despite great interest in sexual selection, relatively little is known in detail about the genetic and environmental determinants of secondary sexual characters in natural populations. Such information is important for determining the way in which populations may respond to sexual selection. We report analyses of genetic and large-scale environmental components of phenotypic variation of two secondary sexual plumage characters (forehead and wing patch size) in the collared flycatcher Ficedula albicollis over a 22-year period. We found significant heritability for both characters but little genetic covariance between the two. We found a positive association between forehead patch size and a large-scale climatic index, the North Atlantic Oscillation (NAO) index, but not for wing patch. This pattern was observed in both cross-sectional and longitudinal data suggesting that the population response to NAO index can be explained as the result of phenotypic plasticity. Heritability of forehead patch size for old males, calculated under favorable conditions (NAO index > or = median), was greater than that under unfavorable conditions (NAO index < median). These changes occurred because there were opposing changes in additive genetic variance (VA) and residual variance (VR) under favorable and unfavorable conditions, with VA increasing and VR decreasing in good environments. However, no such effect was detected for young birds, or for wing patch size in either age class. In addition to these environmental effects on both phenotypic and genetic variances, we found evidence for a significant decrease of forehead patch size over time in older birds. This change appears to be caused by a change in the sign of viability selection on forehead patch size, which is associated with a decline in the breeding value of multiple breeders. Our data thus reveal complex patterns of environmental influence on the expression of secondary sexual characters, which may have important implications for understanding selection and evolution of these characters.

Sexual selection predicts advancement of avian spring migration in response to climate change

“…Our hypothesis is independent of these inconsistencies, however, since sexual selection on traits exhibiting environment-dependent phenotypic plasticity is not uncommon (e.g. Garant et al 2004;Saino et al 2004). Degree of change in arrival date could therefore have a sexually selected component (e.g.…”

Conditions on the Mexican moulting grounds influence feather colour and carotenoids in Bullock's orioles (Icterus bullockii)

“…This finding is particularly important because tail ornament length is directly linked to reproduction (Saino et al., 2004). Similarly, ornament production has been linked to over‐wintering conditions in both pied ( Ficedula hypoleuca ) and collared flycatchers ( Ficedula albicollis ), which also molt in sub‐Saharan Africa (Garant, Sheldon, & Gustafsson, 2004; Järvistö, Calhim, Schuett, & Laaksonen, 2016). In North America, yellow warblers ( Setophaga petechia ) undergo a pre‐alternate molt of body feathers on the wintering grounds; birds overwintering in higher‐quality habitat (inferred via stable isotope analysis) produced more colorful feathers (higher chroma), which are important for mate choice during breeding (Jones, Drake, & Green, 2014).…”

Experimental manipulation shows that the white wing patch in collared flycatchers is a male sexual ornament

“…After measuring them, male collared flycatchers were random systematically assigned to treatment groups within the experiment by tossing a coin at the start of every catching day and then alternating treatments throughout that catching day. The measurement of "wing patch" in published literature on this population (e.g., Sheldon and Ellegren 1999;Garant et al 2004) specifically refers to the amount of white on the outer primaries measured as described above. However, collared flycatchers have a band of white (which is particularly large in males) that extends almost over the full length of the wing, including the secondary wing feathers and the tertials.…”

“…Most studies have focused their attention on the importance of the forehead patch in mate selection. The size of the forehead patch is heritable (Garant et al 2004;Qvarnström et al 2006), and condition dependent (Gustafsson et al 1995;Garant et al 2004). Male ornament and male annual fitness are positively correlated on the genetic level indicating that genes for a large forehead patch also code for high fitness .…”

“…Yet, males clearly display their wing patches during courtship behavior, both during male-male competition (Török et al 2003) and courtship flights. Garant et al (2004) shows that the size of the forehead patch and that of the wing patch are weakly genetically correlated (genetic correlation of 0.12 ± 0.02 [SE] in adults).…”