Melanin‐based ornament darkness positively correlates with across‐season nutritional condition

Abstract

Condition-dependence is a fundamental concept in sexual selection research. Costs of mate choice (in terms of time, energy, and opportunity) necessitate benefits that outweigh these costs. A major group of benefits arises from condition-dependence, which means the adjustment of signals to the physiological state of the individual, as a consequence of the costs of expressing elaborate signal values (Penn & Számadó, 2020). Condition-dependence may link signal expression to the additive genetic background of condition (Rowe & Houle, 1996), thereby building a connection between mate choice and adaptation to the prevailing environment (Lorch et al., 2003), at the same time also lessening the chance that directional selection by mate choice depletes the additive genetic variance of the signal (Tomkins et al., 2004). Recent research of condition-dependent signals has brought new suggestions for general mechanisms connecting organismal performance and signal expression (Emlen et al., 2012; Koch et al., 2017; Lailvaux & Irschick, 2006). Another promising direction might be the use of overarching, multidimensional approaches to condition (Milot et al., 2014). At the same time, a tendency is seen for the preservation (Labocha & Hayes, 2012), reinstatement (Schulte-Hostedde et al., 2005), and reinterpretation (Salin et al., 2015) of classical condition measures. All of these developments make sense only if we (a) clarify the timing and mechanism of signal production and (b) also take into account the possibility that signal expression may feed back to condition, for example, through resource acquisition (Klug et al., 2010) or aggression by conspecifics (Webster et al., 2018).

The signalling function of plumage colour traits in the Chestnut Thrush (Turdus rubrocanus)

“…For the wing, a higher PC1 score corresponds to higher chroma and brightness. The repeatability of spectral variables was calculated using rptR in R (Hegyi et al 2020) and was relatively high between consecutive spectra of the same individuals (Table A1), so we used the mean of the five measurements per body patch in the following analyses.…”

“…2019, Hegyi et al . 2020), and previous studies have found that outcomes can be affected by sex‐dependent life history strategies and hormone levels (Emaresi et al . 2014, Immonen et al .…”

“…In monochromatic species, the same plumage patch could signal different information in the two sexes (Fargallo et al 2013, L opez-Idi aquez et al 2019, Hegyi et al 2020, and previous studies have found that outcomes can be affected by sex-dependent life history strategies and hormone levels (Emaresi et al 2014, Immonen et al 2018. For example, activity was negatively related to bib size in free-living male Eurasian Tree Sparrows Passer montanus, whereas the association was positive in females (F€ ul€ op et al 2021).…”

Canalised and plastic components of melanin-based colouration: a diet-manipulation experiment in house sparrows

“…calcium; 19). In blackcaps ( Sylvia atricapilla ), darkness of melanin-based ornaments positively correlated with nutritional condition across seasons 40 , however, it is not known whether the effect was caused by general diet restriction or restriction of a specific diet component. In addition to the components of the diet, other condition-related factors (e.g.…”

Family resemblance in color‐patch size is not affected by stress experience in a cichlid fish

“…These metabolic processes allow carotenoid‐based coloration to respond to environmental and physiological changes (e.g., Rosenthal et al., 2012 ). Attention has also been drawn to the condition dependence and the resulting information content of melanin‐based coloration (Griffith et al., 2006 ; Hegyi et al., 2020 ; Minias et al., 2019 ; Roulin, 2016 ; Sly et al., 2022 ). Melanin pigments are endogenously synthesized from amino acids and observed correlations between integumentary melanin concentration (perceived as blackness) and body condition have been hypothesized to arise from production or display costs or from pleiotropic genetic effects (Hegyi et al., 2020 ; Roulin, 2016 ).…”