Melanin coloration has temperature-dependent effects on breeding performance that may maintain phenotypic variation in a passerine bird.

Fluctuating selection pressure may maintain phenotypic variation because of different types of individuals being adapted to different environmental conditions. We show that the extensive variation in the coloration of male pied flycatchers (Ficedula hypoleuca) can be maintained through differences in the reproductive success of male phenotypes under different conditions. The effects of weather conditions on the relative success of different male phenotypes varied between different phases of breeding. The reproductive output of black males was the highest when it was cold during egg-laying but warm during the nestling period, whereas the fledgling production of brown males was highest when it was continuously warm. In addition, male forehead and wing patch sizes had context-dependent effects on timing of breeding and nestling mortality, respectively. These results indicate that environmental heterogeneity plays a role in maintaining phenotypic variation. As melanin-based coloration is heritable, climate change may alter phenotype frequencies depending on the patterns of warming.

Sirkiä PM ，Virolainen M ，Laaksonen T 《-》

[Structural and functional aspects of variation of the breeding plumage ornamentation in the male Pied Flycatcher Ficedula hypoleuca (Aves: passeriformes)].

Ivankina EV ，Kerimov AB ，Grin'kov VG ，Bushuev AV ... -  《ZHURNAL OBSHCHEI BIOLOGII》

Evidence for sexual selection on structural plumage coloration in female eastern bluebirds (Sialia sialis).

Siefferman L ，Hill GE 《EVOLUTION》

Elevated oxidative stress in pied flycatcher nestlings of eumelanic foster fathers under low rearing temperatures.

Striking variation in melanin coloration within natural populations is likely due to the different fitness outcomes of alternative phenotypes in varying environmental conditions. There are two types of melanin: eumelanins yield blackish hues, whereas pheomelanins yield reddish hues. The production of eumelanins requires low levels of glutathione (GSH), which is the most important intracellular antioxidant, whereas the production of pheomelanins requires high levels of GSH. We investigated the oxidative status of male pied flycatchers (Ficedula hypoleuca) with different degrees of melanin coloration under different temperatures during the nestling period. Moreover, we assessed the oxidative status of offspring in relation to their biological or foster father's melanin coloration and ambient temperature. To separate offspring genotype effects and paternal effects in different temperatures, we used a partial cross-foster design. The temperature differently affected the oxidative status of differently colored male pied flycatchers and their foster offspring. When the weather was relatively cold, black males had higher glutathione S-transferase levels compared with brown males, indicating enhanced stress in black males. Foster offspring of black males had a lower ratio between reduced and oxidized GSH followed by higher total amount of GSH than foster offspring of brown males. Thus, foster offspring of black males seem to suffer from oxidative stress under relatively cold weather compared with those of brown males, and vice versa under relatively warm weather. Although differently colored males experienced changes in their oxidative status under different temperatures, the link between paternal melanin coloration and offspring oxidative stress appears to be environmentally induced.

Teerikorpi PE ，Stauffer J ，Ilmonen P ，Calhim S ，Schuett W ，Laaksonen T ... -  《-》

Natural selection and genetic variation for reproductive reaction norms in a wild bird population.

Brommer JE ，Merilä J ，Sheldon BC ，Gustafsson L ... -  《EVOLUTION》