Movement ecology
Nonrandom dispersal and evolutionary divergence: insights from a wild bird population Carlos Camacho∗†1 , David Canal1 , and Jaime Potti1 1
Department of Evolutionary Ecology, Estaci´on Biol´ogica de Do˜ nana (EDB-CSIC), Am´erico Vespucio s/n, 41092, Seville, Spain
Abstract Gene flow has long been considered as a force opposing the diversifying effects of natural selection. Recent research, however, has challenged this traditional assumption by revealing new ways in which gene flow through dispersal can reinforce evolutionary change. Here, we report an intriguing pattern of genetic and phenotypic differentiation at a small spatial scale (1.1 km) in pied flycatchers (Ficedula hypoleuca) inhabiting deciduous and coniferous habitats over 25 years. Unlike females, males in the deciduous forest had larger tarsi than those in the coniferous site. Males — and to a lesser degree, females — moved between habitats according to their body size. Large-sized individuals settled to breed in the deciduous forest, regardless if they originated from the coniferous site; the reverse was true for smaller ones, which were more often found in the coniferous forest. Besides morphological differentiation, nonrandom dispersal also resulted in a low but significant genetic differentiation. Male distribution did not reflect genotype- or condition-dependent dispersal. Nor does it result from matching habitat choice, by which similar phenotypes segregate together in the habitats they are best suited to, and thus enhance fitness. We conclude that the spatial sorting of pied flycatcher phenotypes is likely explained by the species’ deeply-rooted preference for deciduous habitats, leading to dominance of the largest males and competitive exclusion of the smaller ones toward the underappreciated coniferous forest. Our results illustrate how population differentiation can occur under directional gene flow, even at an exceedingly small spatial scale.
Keywords: population differentiation, population structure, dispersal, Ficedula hypoleuca, matching habitat choice, pied flycatcher
∗ †
Speaker Corresponding author:
[email protected]
38
