Fig. 1: Strong environmental selection pressure leading to the various alterations in the L- and H-population.

a Plot depicting oxygen level and the generations for L-population (blue line) and H-populations (orange line) (Source data are provided as Fig. 1a Source Data), b Estimated vs observed population size and error bands correspond to 95% confidence interval for the regression coefficient (Pearson’s R) (Source data are provided as Fig. 1b Source Data), c Estimated population size at different generations under selection pressure of L and H environments (Source data are provided as Fig. 1c Source Data), and d Principal Component Analysis (PCA) depicting PC1 and PC2 for the three replicates of L-, H-, and N-populations explains 45% of the variance (Supplementary Fig. 1a). The PCA was performed using only extant single nucleotide polymorphisms (SNPs) (Source data are provided as Fig. 1d Source Data). L-population, the population evolving in hypoxic environments; H-population, the population evolving in hyperoxic environments; N-population, the population maintained in normoxic environment.