Many species are subdivided into a mosaic of genetically distinct populations, which are separated by narrow hybrid zones. By measuring the frequency of genotypes across such hybrid zones, we can estimate the rate of gene flow, the strength of selection etc. - quantities that would be very hard to measure directly.

Many species are subdivided into a mosaic of genetically distinct populations, which are separated by narrow hybrid zones. By measuring the frequency of genotypes across such hybrid zones, we can estimate the rate of gene flow, the strength of selection etc. - quantities that would be very hard to measure directly.

We are studying the ecological and evolutionary dynamics of hybrid zones between two species of Antirrhinum (snapdragons) with different flower colours (yellow and magenta - pictured). In this system, two major loci control flower colour, giving rise to six colour phenotypes across a narrow hybrid zone. This raises the question as to how the alleles that control the distinct phenotypes arise and spread despite strong barriers to invasion into parental populations. In collaboration with researchers in the UK (Enrico Coen’s group in Norwich) and Toulouse (Christophe Andalo and Monique Burrus) and Vienna (David Field), we are using a range of ecological field work, population genetic and genomic approaches to gain a better understanding of how species diverge during the speciation process. Some of the projects we (Nick Barton, David Field, Melinda Pickup, Maria Clara Melo, Lenka Matejovičová) are working on in the group include: (1) reconstruction of a large-scale multi-generational pedigree to examine the fitness landscape for interacting alleles that control the colour space, (2) the topology of divergence and cline behaviour across the genome to determine how alleles arise and spread and what barriers exist to their dispersal, (3) the role of pollinator behaviour and frequency dependence in hybrid zone maintenance, (4) Self incompatibility and introgression of the genome.

The dynamics of hybrid zones also apply to biocontrol programmes where the introduced agent only increases above a threshold.  Nick Barton is working with Michael Turelli to optimise a program to eliminate dengue fever and other diseases by releasing Wolbachiai infected mosquitoes (EliminateDENGUE).

A. majus spp. striatum (left), A. majus spp. pseudomajus (right) and their hybrids (middle)
Antirrhinum hybrid zone