Nonrandom dispersal drives phenotypic divergence within a bird population

Abstract

Gene flow through dispersal has traditionally been thought to function as a force opposing evolutionary differentiation. However, directional gene flow may actually reinforce divergence of populations in close proximity. This study documents the phenotypic differentiation over more than two decades in body size (tarsus length) at a very short spatial scale (1.1 km) within a population of pied flycatchers Ficedula hypoleuca inhabiting deciduous and coniferous habitats. Unlike females, males breeding in the deciduous forest were consistently larger than those from the managed coniferous forest. This assortment by size is likely explained by preset habitat preferences leading to dominance of the largest males and exclusion of the smallest ones toward the nonpreferred coniferous forest coupled with directional dispersal. Movements of males between forests were nonrandom with respect to body size and flow rate, which might function to maintain the phenotypic variation in this heritable trait at such a small spatial scale. However, a deeply rooted preference for the deciduous habitat might not be in line with its quality due to the increased levels of breeding density of hole-nesting competitors therein. These results illustrate how eco-evolutionary scenarios can develop under directional gene flow over surprisingly small spatial scales. Our findings come on top of recent studies concerning new ways in which dispersal and gene flow can influence microevolution.

Long‐term occupancy of nest boxes as a measure of territory quality for Pied Flycatchers

“…Songbird reproduction has been monitored in the two habitats over 22 yr (1995–2017), except for 2003 when sampling was limited (e.g., Camacho et al. , , , ).…”

“…Nest‐box availability for Pied Flycatchers (i.e., empty nest boxes not occupied by other species) decreased during the study period due to increases in populations in both forest patches (Camacho et al. ). However, population growth was greater in the pinewood, where saturation of nest box occupation by Pied Flycatchers and other species is already manifest.…”

From early life to senescence: individual heterogeneity in a long‐lived seabird

“…Spatial distribution seems closely related to individual features (Coulson , Camacho et al. ); more competitive individuals may have access to high quality habitats, constraining subordinate individuals to settle in marginal habitats (van de Pol et al. , Oro ).…”

Ontogenetic variation in the plumage colour of female European Pied Flycatchers Ficedula hypoleuca

“…Camacho et al . ), the first author noted clear differences in female plumage colour in birds in the hand, with some looking much darker than others (Fig. ).…”