Phylogeography, hybridization and speciation
Populations within a species that stop exchanging individuals will start diverging genetically due to random changes in gene frequencies between generations. Such neutral genetic differences can be used to assign the identity of individuals to populations, identify barriers to historical and present gene flow, and infer post-glacial colonization routes. In this context we use neutral genetic markers (mtDNA, microsatellites and AFLP) to study migratory connectivity, local adaptations and hybridization between populations that meat again after generations of isolation. The end point of the process that starts with the divergence of populations is speciation. By studying the forces of genetic drift, selection and hybridization in incipient species, we can learn about the mechanism of speciation, a research field that has been active ever since Darwin.

Projects:



Genetics of the migratory program in willow warblers

The willow warblers is one of the most common breeding species in Sweden. There is a sharp migratory divide in central Scandinavia which is associated with several other trait differences correlated to the two migration patterns: smaller and greener birds in southern Scandinavia migrates towards SW for wintering in west Africa whereas larger, greyer birds in northern Scandinavia migrates towards SE for wintering in central, east and south Africa. All these traits seem to have evolved within the last 10,000 years during the process of postglacial colonization of northern Europe. What kind of selection is maintaining the migratory divide; assortative mating or ecological selection against hybrids? To answer these questions we use stable isotope analyses to infer wintering areas of individual birds, microsatellite markers, AFLP and nuclear gene sequencing. A long term goal is to isolate genes involved in the migratory program.



Members: Staffan Bensch, Susanne Åkesson, Mats Grahn.



Population structure and migratory flyways of Red Admirals

The Red Admiral is a widespread migratory butterfly that can be found all over Europe, most parts of Asia and North America. In Europe it spends the winters close to the Mediterranean Sea and each spring it spreads out northwards to return back again next winter. Even though its migration has been the subject of research for over 40 years we still do not know much about the population structure and migratory flyways of this species. To better understand this migratory system we use AFLP to look for population structures within Europe and stable isotopes to learn more about the phenology of this migration.

Members: Oskar Brattström, Staffan Bensch, Susanne Åkesson,



Hybrid zones of temperate species of birds

All species of animals and plants now occurring in regions that were glaciated during the last ice-age have changed their ranges dramatically over the past 10,000 years. For many species the colonization originated from several refuge populations that, due to isolation during the ice-ages, have accumulated varying levels of genetic differences. This can now been seen as contact zones between more or less divergent populations, often involving some hybridization between the taxa. Our recent studies of hybrid zones involve chaffchaffs, greenish warblers, icterine and melodious warblers, spotted and lesser spotted eagles.

Members: Staffan Bensch

References:

Bensch, S. Helbig, A. J., Salomon, M. & Seibold, I. 2002. AFLP analysis identifies hybrids between two subspecies of warblers. Molecular Ecology 11: 473-481.

Irwin, D. I., Bensch, S., Irwin, J. H. & Price, T.2005. Speciation by distance in a ring species. Science 307: 414-416.

Helbig, A. J., Seibold, I., Kocum, A., Liebers, D., Irwin, J., Bergmanis, U., Meyburg, B.-U., Scheller, W., Stubbe, M. & Bensch, S. 2005. Genetic differentiation and hybridization between Greater and Lesser Spotted Eagles (Accipitriformes: Aquila clanga, A. pomarina). Journal of Ornithology 146, 226-234.

Secondi, J., Faivre, B. & Bensch, S. 2006. Spreading introgression in the wake of a moving hybrid zone. Molecular Ecology, 15: 2463-2475.