Fig. 3: Effective population sizes and coalescence simulation.

a Effective Population size plot over time using the same mutation rate and eight of the most diverse isolates in populations. The dashed lines indicate the two recent hybrid populations. b Cross-coalescence analysis over time from the same dataset as in a. The blue line indicates a pair with B.g. dicocci, the green line indicates a pair with the USA population, the orange indicates a pair with the ARG mildew population, and the black line indicates a pair between the rest of the Eurasian populations. The dashed line indicates the threshold of one under which separation starts. The grey line with the number “1” refers to the late separation of the American populations from the rest (event 1) and the grey line with the number “2” refers to the approximate start of separation of the ISRdic from the other populations (event 2), while the number “3” grey line refers to the early separation of the American mildew populations from the rest (event 3). c Results of fastsimcoal2 analysis with the model schemes. The three best models are depicted (the rest are in Supplementary Fig. 17). The DeltaL and AIC values are depicted below the Scenario name in bold and non-bold letters, respectively. d Evidence for ancient hybridizations of mildews in North and South America. Mildew populations from USA and Argentina share numerous ancestral SNPs with distantly related (outgroup) grass mildews (colors indicate the number of outgroup isolates in which the SNP was found to be varied). The black asterisks on top indicate shared SNPs between the Argentinian and USA mildew populations. The red boxes indicate chromosomal windows that were under selection exclusively in the ARG or USA population.