BRS: Staffan Bensch "Unfolding the elusive migratory direction genes in the willow warbler genome"

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Abstract: Understanding the genetic architecture of the migratory program is a research field in its infancy - no gene has so far been conclusively identified as linked to the expression of  different  migratory behaviours. The willow warbler Phylloscopus trochilus has two migratory divides located in central Scandinavia and south of the Baltic Sea. Smaller and greener birds of the subspecies trochilus breed in southern Scandinavia and migrate towards SW for wintering in western Africa whereas larger, grayer birds of the subspecies acredula breed in northern Scandinavia and Finland and migrate towards SE for wintering in east and south Africa. Absence of differences at neutral loci between the subspecies suggested that the phenotypic trait differences have evolved within the last 10,000 years during the process of postglacial colonization of northern Europe. Population samples of willow warblers around the Baltic demonstrate that several different traits including coloration, size, migratory direction (inferred from stable isotope analyses) and three independent chromosomal blocks, show drastically different cline patterns along the eastern side of the Baltic, supporting that the willow warbler has colonized Scandinavia via two directions from one common glacial refuge population. New data from whole genome resequencing and genotyped birds with geolocator tracks from the hybrid zone demonstrate that finding genes involved in the migratory program is challenging, but that the willow warbler system provides promising directions of research that might finally lead to a breakthrough in this field.