Fig. 5: Putative evolutionary history of sex determination in Pristionchus.
a Difference in coverage depth of chromosome-specific 21-mers between sexes. The category labelled as ‘Others’ contains data from all other chromosomal elements (i.e. NigonA, NigonB, NigonC and NigonD). All biological replicates are shown as jitter plots (N = 8 for P. fissidentatus, P. atlanticus and P. mayeri; N = 5 for P. pacificus, P. exspectatus, P. aerivorus) while the box plot shows statistics (upper whisker, the largest data point less than the third quartile +1.5 × interquartile range; upper bound, the third quartile; centre line, median; lower bound, the first quartile; lower whisker, the smallest data point more than the first quartile −1.5 × interquartile range). The average log2 coverage depth of each chromosome for each species is normalized with the autosomal average and compared between randomly paired male and female (or hermaphrodite) individuals. In each species, the log2 sex differences of three Nigons were compared with that of ‘Others’ and tested with Wilcoxon-Mann–Whitney test (W = 102, 115, 256, 35, 26, 100, 47, 43, 100, 169, 117, 256, 39, 55, 50, 187, 145, and 115, from top to bottom, two-sided Bonferroni-adjusted p = 1, 1, 7.80 × 10−8, 1, 0.337, 1.13 × 10−4, 0.523, 1, 7.80 × 10−8, 1, 1, 1, 0.139, 1, and 1, from top to bottom). The two-sided Bonferroni-adjusted p-values are shown as stars (p > 0.05, N.S.; *p < 0.05, **p < 0.01, ***p < 0.001). b Phylogenetic estimation of chromosome evolution. Left schematic diagrams with coloured bars that corresponds to Nigon elements (NigonE, orange; NigonN, pink; and NigonX, green) represent diploid chromosome patterns of each sex. Chromosome patterns of P. atlanticus and P. aerivorus (marked with star ‘*’) were inferred using karyotyping (Fig. 1h) and coverage data (a). Evolutionary events were determined parsimoniously.
