Fig. 3: Evolutionary strata of four nematode sex chromosomes.

For the X of each species, the component Nigon elements correspond to strata inferred based on the presence of mappable Y-linked sequences, male vs. female ratios of mapped read coverage and SNP densities, and repeat densities. All metrics were estimated for 50-kb long, 10-kb overlapping windows. For Brugia malayi and Onchocerca volvulus, the orthologous genes (vertical lines) are colour-coded according to their different Nigon elements. For Trichuris muris, B. malayi and O. volvulus, the Y-linked sequences that could be assembled along the X are colour-coded according to their pairwise sequence divergence between the X/Y, and the log2 male vs. female SNP density ratios and the repeat density on the X are indicated by colour-codes. Strata are labeled S0 for the oldest stratum, followed by S1, S2, etc.). PAR stands for the pseudoautosomal region.