Age-dependent relationships between multiple sexual pigments and condition in males and females

Abstract

The reliability of sexual signaling may change across age classes due to shifts in resource allocation patterns. Two contrasting hypotheses exist regarding how the condition dependence of ornaments may shift with age, and both have received empirical support. On one hand, ornaments may more reliably reflect condition and quality in older individuals, because younger individuals of high quality invest in survival over signaling effort. On the other hand, the condition dependence of ornaments may decline with age, if older individuals in poor condition terminally invest in ornaments, or if resource constraints decline with age. Further, the expression and condition dependence of different ornaments may shift with age in unique ways, such that multifaceted sexual displays maintain reliable signaling across age classes. In yellow warblers (Setophaga petechia) of both sexes, we assessed how relationships between carotenoid-and phaeomelanin-based sexual pigmentation, prenesting body reserves, and condition at molt (reflected by growth bars and feather quality) vary across age classes. Melanin coverage correlated with condition at molt across age classes in males and showed high repeatability in both sexes. In contrast, carotenoid saturation increased longitudinally with age in males and correlated with condition at molt in different age classes in the 2 sexes. Specifically, carotenoid saturation correlated positively with condition at molt in younger, but not older males, whereas in females, the situation was reversed, with a positive correlation present only in older females. Results suggest that age-dependent signaling may promote maintenance of multifaceted sexual displays and that agedependent signaling dynamics depend on sex.

Quantitative color variation within and across morphs of the polymorphic White-throated Sparrow

“…Thus, before obtaining reflectance spectra from feather samples, we did our best to recreate natural plumage configuration by carefully overlapping feathers, an approach that has frequently been adopted by previous researchers (Hõrak et al 2001, Freeman-Gallant et al 2010, Grunst et al 2014). We secured 3 to 5 overlapping feathers to blank white index cards, using clear tape at the base of the feather.…”

Conditional Handicaps in Exuberant Lizards: Bright Color in Aggressive Males Is Correlated with High Levels of Free Radicals

“…Heritable color morphs often have distinct behaviors and physiology, with associated differences in selection pressures on an otherwise common genetic background (Sinervo and Lively, 1996;Pryke and Griffith, 2006;Healey et al, 2007;Pryke et al, 2007;Olsson et al, 2009aOlsson et al, , 2007areviewed in Huxley, 1955;Wellenreuther et al, 2014). Colorful traits often fade during the breeding season, which suggests these traits may have condition-dependent expression and costly to maintain (Cotton et al, 2004;Grunst et al, 2014;Reinhart et al, 2015), which are potentially mediated by oxidative stress (von Schantz et al, 1999;Monaghan et al, 2009;Hõrak et al, 2010;Garratt and Brooks, 2012;Costantini, 2014;Hung and Li, 2015) and body condition (Slagsvold and Lifjeld, 1992;Costantini, 2008;Stephen Dobson et al, 2008). Reactive oxygen species (ROS) damage DNA, proteins and cell membranes, triggering cell death and color-fading (Dowling and Simmons, 2009;Costantini, 2010;Olsson et al, 2012).…”

Sexual pigmentation and parental risk‐taking in yellow warblers Setophaga petechia

“…Further, we used a Stylus 800 Olympus camera to take digital photographs of the front and sides of all birds. For males, we used the threshold colour function in ImageJ to extract the percent coverage of red–brown (phaeomelanin) from photographs (Schneider et al , see Grunst et al for further detail). For most females, melanin coverage was too low to accurately quantify in ImageJ.…”

“…The intensity of carotenoid‐based pigmentation and the amount of phaeomelanin‐based pigmentation are largely uncorrelated in males, and positively correlate in females ( r = 0.41), but with significant independent variation. Thus, the two pigment types may convey non‐equivalent information (Grunst et al ). We have previously established that carotenoid‐ and phaeomelanin‐based pigmentation are associated with metrics of individual condition in both sexes of the yellow warbler (Grunst et al , ), and warblers show assortative social pairing by pigmentation (Grunst and Grunst ).…”

“…Thus, the two pigment types may convey non‐equivalent information (Grunst et al ). We have previously established that carotenoid‐ and phaeomelanin‐based pigmentation are associated with metrics of individual condition in both sexes of the yellow warbler (Grunst et al , ), and warblers show assortative social pairing by pigmentation (Grunst and Grunst ). Further, a past study found greater extra‐pair paternity among males expressing more melanin‐based pigmentation (Yezerinac and Weatherhead ), and in our study population males co‐expressing high levels of both melanin‐ and carotenoid‐based pigmentation lose less paternity in their social broods (Grunst and Grunst ).…”