Life-History Differences in Age-Dependent Expressions of Multiple Ornaments and Behaviors in a Lekking Bird

Abstract

Online enhancements: supplementary tables and figure. Dryad data: http://dx.doi.org/10.5061/dryad.rg8d4.abstract: Age is a major factor explaining variation in life-history traits among individuals with typical patterns of increasing trait values early in life, maximum trait expression, and senescence. However, age-dependent variation in the expressions of sexually selected traits has received less attention, although such variation underpins differences in male competitive abilities and female preference, which are central to sexual selection. In contrast to previous studies focusing on single traits, we used repeated measures of seven sexually selected morphological and behavioral traits in male black grouse (Tetrao tetrix) to quantify the effects of age and life span on their expressions and quantified this variation in relation to male reproductive effort. Trait expression increased with age, but long-lived males had a slower increase and delayed maxima in trait values compared with shortlived males. There was evidence of terminal investment (increasing trait values during the last breeding season) in some traits and senescence in all traits. These trait dynamics were largely explained by the timing of male peak lekking effort. This study shows that fully understanding the variation in sexually selected traits and fitness benefits associated with sexual selection requires accounting for the complex interaction among individual age, life span, and the timing of individuals' investment in reproduction.

Age‐ and quality‐dependent DNA methylation correlate with melanin‐based coloration in a wild bird

“…As our study focused primarily on the correlation between DNA methylation and sexual trait expression, such a pattern is to be expected. Sexually selected traits typically show strong inverse u‐shaped responses with age (e.g., Balbontín, De Lope, Hermosell, Mousseau, & Møller, 2011; Kervinen et al., 2015) so factors associated with expression of these traits such as DNA methylation and gene expression might also be expected to show similar patterns.…”

“…Another important aspect of sexually selected traits is that their expression tends to be highly variable within individuals and often shows patterns of early life improvement, prime age maximum expression, and senescence (Jones et al., 2008; Nussey et al., 2009; Kervinen, Alatalo, Lebigre, Siitari, & Soulsbury, 2015). Hence, relationships between sexually selected traits and individual quality may vary with age, with the strongest relationships being found during periods of maximal trait expression (Hooper, Tsubaki, & Siva‐Jothy, 1999; Von Hardenberg et al., 2007).…”

“…The feathers of the neck and chest also show a blue structural coloration that exhibits high reflectance of short wavelengths in the UV‐blue area (blue chroma; Siitari, Alatalo, Halme, Buchanan, & Kilpimaa, 2007). These sexually selected sexually‐selected traits are condition‐dependent and vary substantially with age (Kervinen et al., 2015; Kervinen, Lebigre, & Soulsbury, 2016). Peak expression occurs at ages 3–5 (Kervinen et al., 2015) and is correlated to male mating success (Siitari et al., 2007; Kervinen et al., 2016).…”

“…These sexually selected sexually‐selected traits are condition‐dependent and vary substantially with age (Kervinen et al., 2015; Kervinen, Lebigre, & Soulsbury, 2016). Peak expression occurs at ages 3–5 (Kervinen et al., 2015) and is correlated to male mating success (Siitari et al., 2007; Kervinen et al., 2016). Furthermore, inbreeding is frequent in our study population, with ca .…”

Simultaneous age‐dependent and age‐independent sexual selection in the lekking black grouse (Lyrurus tetrix)

“…; Evans, Gustafsson & Sheldon ; Kervinen et al . ) most probably through changes in body condition throughout individuals' life span (Höglund & Sheldon ; Emlen et al . ).…”