I answer different key questions in evolutionary biology using different genetic and genomic approaches. The main areas that I am interested in are:
Speciation is the evolution of reproductive isolation between populations and the result of the acquirement of reproductive barriers. We are particularly interested in ecological speciation, that is the evolution of reproductive isolation between populations as a result of adaptation to divergent environments. Ecological studies of natural populations complemented with new genomic methods such as next-generation sequencing allowing large-scale genome and transcriptome sequencing is regarded the way forward for understanding how ecological speciation proceeds. In this project we work with two closely related willow species, Salix viminalis and S. schwerini. Phenotypically they are very similar but their natural distributions are non-overlapping. S. viminalis has a vast natural distribution ranging from Great Britain in the west to Asia in the east. S. schwerinii has a smaller and more eastern distribution. For ecological speciation to occur, divergent natural selection should be the main cause of divergence. Genomic sequence data both within and between species can be used to determine whether divergence between populations is caused by natural selection or neutral processes and will also give information of candidate genes involved in reproductive isolation (speciation genes). With the addition of ecological data one can determine whether exposure to similar environments lead to the evolution of similar adaptations. To achieve these goals one need information about both environmental differences and divergent traits.
The genetic control of sex determination is a fundamental biological process. However, surprisingly little is known about this in Salicaceae, the plant family where willows and poplars belong. In order to increase our understanding of sex determination in plants we plan to map sex in willows and the ultimate goal of this project is to identify the gene/s responsible for sex determination. Unlike the majority of plants, most willows are dioecious and another peculiar feature about willows is their biased sex ratio. Many S. viminalis populations are thus strongly female biased and controlled crosses suggest that sex biases are not a result of environmental effects. We have so far performed a QTL analysis and found one major QTL (7 cM) on linkage group XV. We are currently fine mapping this QTL in order to come closer to individual genes.
Berlin, S., Fogelqvist, J., Lascoux, M., Lagercrantz, U. and Rönnberg-Wästljung, A-C. (2011). Polymorphism and divergence in two willow species, Salix viminalis L. and Salix schwerinii E. Wolf. G3: Genes, Genomes, Genetics 5:1.
Berlin, S., Lagercrantz, U., von Arnold S., Öst, T. and Rönnberg-Wästljung, A-C. (2010). High-density linkage mapping and evolution of paralogs and orthologs in Salix and Populus. BMC Genomics 11:129.
Berlin, S., Quintela, M., Höglund, J. (2008). A multilocus assay reveals high nucleotide diversity and limited differentiation among Scandinavian Willow grouse (Lagopuslagopus). BMC Genetics 9:89.
Berlin, S., Tomaras, D. and Charlesworth, B. (2007). Low mitochondrial variability in birds may indicate Hill-Robertson effects on the W chromosome. Heredity 99:389-396.
Berlin S, Ellegren H. (2004). Chicken W: a genetically uniform chromosome in a highly variable genome. Proceedings of the National Academy of Sciences USA 101:15967-15969.