Fecundity selection does not vary along a large geographical cline of trait means in a passerine bird

Abstract

Local environmental and ecological conditions are commonly expected to result in local adaptation, although there are few examples of variation in phenotypic selection across continent-wide spatial scales. We collected standardized data on selection with respect to the highly variable plumage coloration of pied flycatcher (Ficedula hypoleuca Pall.) males from 17 populations across the species' breeding range. The observed selection on multiple male coloration traits via the annual number of fledged young was generally relatively weak. The main aim of the present study, however, was to examine whether the current directional selection estimates are associated with distance to the sympatric area with the collared flycatcher (Ficedula albicollis Temminck), a sister species with which the pied flycatcher is showing character displacement. This pattern was expected because plumage traits *Corresponding author. Current address: Finnish Museum of Natural History, University of Helsinki, Finland. E-mail: paivi.sirkia@helsinki.fi in male pied flycatchers are changing with the distance to these areas of sympatry. However, we did not find such a pattern in current selection on coloration. There were no associations between current directional selection on ornamentation and latitude or longitude either. Interestingly, current selection on coloration traits was not associated with the observed mean plumage traits of the populations. Thus, there do not appear to be geographical gradients in current directional fecundity selection on male plumage ornamentation. The results of the present study do not support the idea that constant patterns in directional fecundity selection would play a major role in the maintenance of coloration among populations in this species. By contrast, the tendency for relatively weak mosaic-like variation in selection among populations could reflect just a snapshot of temporally variable, potentially environment-dependent, selection, as suggested by other studies in this system. Such fine-grained variable selection coupled with gene flow could maintain extensive phenotypic variation across populations.

Testosterone levels in relation to size and UV reflectance of achromatic plumage traits of female pied flycatchers

“…Geographic variation in male traits among European populations of pied flycatchers has been well studied (Laaksonen et al , Sirkiä et al ), while differences in the same traits on females of this species have received scant attention. It is known that male flycatchers express larger forehead and wing patches in populations of central Spain than in northern populations (Curio ) and it has been recently shown that these differences are partly explained by the degree of divergence from the collared flycatcher in the area of sympatry combined with gene flow (Laaksonen et al ).…”

Climate adaptation and speciation: particular focus on reproductive barriers inFicedulaflycatchers

“…; Sirkiä et al. ). The phenotypic differentiation between the populations ( P ST ) is higher than that in neutral genetic variation ( F ST ), indicating that pied flycatchers have diverged from collared flycatchers simultaneously in all these plumage traits in the area of secondary contact (Lehtonen et al.…”

“…Pleiotropic effects of genes regulating the synthesis of melanins may be one of the key links between climatic adaptations and divergence in eumelanin‐based plumage coloration, which is further suggested to be linked to other intercorrelated plumage characteristics (Sirkiä et al. ). Wiley et al.…”

“…As in the case of ecological character displacement, the socially subordinate species responds stronger to sympatric conditions in terms of reproductive character displacement. In sympatry, male pied dorsal coloration becomes dull brown with less reflectance in UV, and the white patches on the forehead and wing become smaller, while the amount of white in outer retrixes becomes larger Sirki€ a et al 2015). The phenotypic differentiation between the populations (P ST ) is higher than that in neutral genetic variation (F ST ), indicating that pied flycatchers have diverged from collared flycatchers simultaneously in all these plumage traits in the area of secondary contact (Lehtonen et al 2009) and that gene flow from the contact areas may affect coloration around the wide distribution of the species .…”

Phenotypic plasticity in breeding plumage signals in both sexes of a migratory bird: responses to breeding conditions

“…UV reflectance of white patches has been analyzed in other studies of the species (Lehtonen et al , Sirkiä and Laaksonen ). In this study we focus on the area of these plumage patches as in other studies of the species (Galván and Moreno , Lehtonen et al , Lobato et al , Moreno et al , , , Cantarero et al , , Laaksonen et al , Sirkiä et al , Plaza et al ). Moreover, we have previously shown that area and UV reflectance of wing patches are positively correlated, at least in females (Cantarero et al ).…”