Population divergence and gene flow in two East Asian shorebirds on the verge of speciation

Genetic isolation of populations over evolutionary time leads to the formation of independent species. We examined a pair of shorebirds - the Kentish Plover Charadrius alexandrinus and the enigmatic White-faced Plover C. dealbatus - which display strong plumage differentiation, yet show minimal genetic divergence based on previous mitochondrial and microsatellite work. We compared the genotypes of 98 plovers (59 Kentish Plovers, 35 White-faced Plovers and 4 genomic hybrids) sampled in eastern Asia and Europe using ddRADSeq to harvest over 8000 genomewide SNPs. In contrast to previous studies, our analyses revealed two well defined genomic clusters, with limited hybridization and a narrow contact zone. Our results support the hypothesis that this shorebird duo is on the verge of speciation.