The modulatory role of recombination
There is an emerging picture that the genetic architecture of adaptation is shaped by complex dynamics between natural selection, gene flow, and the recombination landscape (i.e. patterns of linkage). I am working towards understanding these dynamics through empirical and theoretical studies. Examples of work so far include:
Recombination rate and divergence
A number of studies have suggested that patterns of genomic divergence between populations are heavily dependant on local variation in recombination rate. In particular, several models predict that adaptive alleles should be over-represented in regions of low recombination, particularly when adaptation occurs in the face of gene flow.
To test this idea, my colleagues and I created a large dataset of genomic data from pairs of stickleback populations from around the world that vary in the presence of gene flow and divergent selection. We discovered that the co-occurrence of strong divergent selection and gene flow causes patterns of genomic divergence to be highly localized in regions of low recombination.
This result provides direct support for the role of local variation in recombination rate driving patterns of divergence in the genome.
Linkage dynamics profoundly shapes the dynamics of adaptive introgression
Adaptive introgression between populations can facilitate adaptation to new environment. However, genetic linkage between globally adaptive alleles and alleles that maintain species boundaries could result in the collapse of species boundaries and the loss of biodiversity.
My colleague Greg Owens and I modelled this scenario using state-of-the-art genetically explicit forward time population genetic simulations. We discovered that linkage between globally adaptive alleles and reproductive isolation alleles can readily result in the collapse of species boundaries, particularly under realistic scenarios of climate change.
This result demonstrates the importance of modelling linkage and recombination in the evolutionary process, and makes novel predictions about potential mechanisms of species loss due to climate change.