Genomic dissection of barriers to gene flow in hybridising fire-bellied toads (2016–2018)

The process of speciation involves the accumulation of genetic factors that reduce gene flow between differentiated populations and can be envisaged at the genomic level as the gradual spread of chromosomal regions that are barred from introgression. At present, we know little about the critical intermediate stage of the process between tentative beginnings and near-completion. The classic Bombina hybrid system promises unique insights into this part of the speciation continuum: despite ancient and profound ecological divergence, B. bombina and B. variegata continue to produce abundant fertile recombinants in narrow hybrid zones. We aim to generate a linkage map from newly created genetic markers and to annotate this map with estimates of introgression rates, QTL for adaptive traits and factors that reduce hybrid fitness. We will test theoretical predictions about efficient gene flow barriers and delineate the scope for ecological speciation in Bombina. More than 1000 DNA samples are available for analysis from experimental crosses and from the hybrid zone in Romania.