2 MATERIAL AND METHODS
We used tissues from the material collected in 1975 (Allendorf et al., 1976; Ryman et al., 1979) that have been stored at -30°C. We first applied a 96 SNP fluidigm array to verify that the existence of the sympatric populations can be detected by markers other than allozymes. Next, we sequenced whole genomes from several pooled individuals (Pool-seq; Kofler, Langmüller, Nouhaud, Otte, & Schlötterer, 2016) as well as from two separate individuals of each deme.