Data package includes 1 excel file named "elegans.assurance" with the following sheets: 1. lab.adapted.male.freq. Figure 2 and additional figure 1 data. Column "block" indicates the time block of each assay, "generation" the (P)arental or F1 generation measured, "NaCl" the NaCl concentration to which worms were exposed to from L1 stage to adulthood before reproduction, and "no.males" the number of males scored out of 300 individuals. 2.inbred.survivorship. Additional figure S2 data. Column "inbred.line" designates the wormbase acronym of the lines, "parent.NaCl" the NaCl concentration to which the parental generation was exposed to, "progeny.NaCl" the NaCl concentration to which the offspring generation was exposed to, and "no.progeny" the number of offspring per hermaphrodite measured. 3. ee.male.freq. Figure 4B and additional figure 6 data. Column "block" indicates the time block of each assay, "generation" the generation of experimental evolution, "population" the wormbase acronym of the population measured (additional table 1), and "no.males" the number of males scored out of 300 individuals. 4.ee.fog2.freq. Figure 4C data. "generation" designates the generation of experimental evolution, "population" wormbase acronym of the population measured (additional table 1), "no.individuals" the number of individuals genotypes at the fog-2 locus, "fog2(wt).freq" the wild type allele frequency, "fog2(wt/q71).freq" the heterozygote frequency 5.pop.fitness. Figure 4D-E, additional figures 3,4, 5 data. Column "block" indicates the time block of each assay, "population" the wormbase acronym of the population measured (additional table 1),"generation" the generation of experimental evolution, "NaCl" the NaCl concentration at which the assay was performed, "setup.ratio" the relative frequency of wild-type alleles at the L1 seeding competition set-up, "competition" the replicate assay, "no.GFP" the number of GFP individuals scored, "no.WT" the number of wild type individuals scored. 6. fertility.male.GFP. Figures 2B, 3A data. Column "block" indicates the time block of each assay, "population" the wormbase acronym of the population measured (additional table 1), "generation" the generation of experimental evolution, "NaCl" the NaCl concentration at which the assay was performed, "breeding.mode" whether hermaphrodites/females were outcrossed to GFP tester males or hermaphrodites selfed, "no.progeny" the number of adult offspring from each individual. 7. fertility.rates. Figures 2C, 3B, 7B data. Column "population" indicates wormbase acronym of the population measured (additional table 1), "generation" the generation of experimental evolution, "time" the hours of the life-cycle where the measurements were done (figure 1B), "NaCl" the NaCl concentration at which the assay was performed, "assay.plate" the replicate plate, "individual" the handpicked individual designation, and "fertile" whether the individual was fertile or not. 8. SNP genotype. Figure 5 and Table 1 data. Column "population" designates wormbase acronym of the population measured (additional table 1), "generation" the generation of experimental evolution, following 58 columns the wormbase designation for each of the SNPs measured. Coding of these 58 columns is "1" for homozygosity for the reference N2 isolate strain allele, "0" for heterozygous genotypes, "-1" for homozygosity for the alternative allele, and "NA" for missing data. 9.male.fitness. Figure 7A data. Column "block" indicates the time block of each assay, "population" the wormbase acronym of the population measured (additional table 1), "generation" the generation of experimental evolution, "no.females" the number of fog-2 tester females whose fertility was measured, "no.GFP" the number of GFP adult individuals scored, and "no.WT" the number of wild type individuals scored.