Our long-term data and linkage map of a Swedish population of great reed warblers provide unique opportunities to study the genetics of evolutionary important traits in a natural population. Recently, we have initiated QTL-analyses with a special focus on wing length; a highly heritable trait that may evolve in response to migratory distance in passerine birds. The great reed warbler is a long-distance migrant that spend the winters in tropical Africa. The wing morphology is of interest for flight performance and optimal migration in this and other long-distance migrants. In recent studies, we have detected a strong association between markers located on chromosome 2 and heritable genetic variation for wing length. The extended linkage disequilibrium in the Swedish great reed warblers facilitates the search for QTL, but also set the limits to the mapping resolution.
We will increase the coverage and marker density of our linkage map by adding newly developed markers, including more than 100 recently isolated microsatellites. To increase the coverage even further, we will also perform RAD (Restriction site Associated DNA) sequencing where a large set of SNPs can be detected and genotyped simultaneously in a large set of individuals. We will then conduct QTL mapping on wing length and other traits, such as body size (an interesting trait in the context of migration and climate change), and song repertoire size (of interest in the context of sexual selection). Main aims are to evaluate hypotheses for the genetic architecture of quantitative traits and the importance of epistatic gene interactions. To evaluate the evolutionary dynamics of the traits and the QTLs, the maintenance of genetic variation, and the importance of ongoing and historical selection pressures, we will simultaneously run selection analyses in the Swedish study population and perform population genetic analyses across the species breeding range.
Hansson B, Åkesson M, Slate J, Pemberton JM (2005) Linkage mapping reveals sex-dimorphic map distances in a passerine bird. Proceedings of the Royal Society, London, Series B, 272, 2289-2298.
Tarka M, Åkesson M, Beraldi D, Hernández-Sánchez J, Hasselquist D, Bensch S, Hansson B (2010) A strong quantitative trait locus for wing length on chromosome 2 in a wild population of great reed warblers. Proceedings of the Royal Society, London, Series B, 277, 2361-2369.