(a-b) Gene Size differs between autosomes and the X chromosome in C. briggsae (Kruskal-Wallis χ
2 = 24.63, df = 1, p < 6.96x10−7), C. elegans (Kruskal-Wallis χ
2 = 58.04, df = 1, p < 2.56x10−14) and C. remanei (Kruskal-Wallis χ
2 = 99.10, df = 1, p < 2x10−16) but protein size does not (C. briggsae Kruskal-Wallis χ
2 = 0.94, df = 1, p = 0.66; C. elegans Kruskal-Wallis χ
2 = 0.29, df = 1, p = 1; C. remanei Kruskal-Wallis χ
2 = 4.3096, df = 1, p = 0.08). Gene size differs significantly among the species on autosomes (Kruskal-Wallis χ
2 = 152.86; df = 2, p < 2x10−16; Bonferroni-adjusted Pairwise Wilcoxon Rank Sum C. remanei:C. elegans
p < 2x10−16, C. remanei:C. briggsae
p < 2x10−16; C. briggsae:C. elegans
p < 6x10−5) and between C. remanei and the self-fertile hermaprodites on the X chromsome (Kruskal-Wallis χ
2 = 64.39; df = 2, p < 1x10−14; Bonferroni-adjusted Pairwise Wilcoxon Rank Sum C. remanei:C. elegans
p < 2x10−10, C. remanei:C. briggsae
p < 1.8x10−11; C. briggsae:C.elegans
p = 1). (c-d) Protein size differs significantly between C. briggsae and C. elegans and C. briggsae and C. remanei on both the autosomes (Kruskal-Wallis χ
2 = 91.32; df = 2, p < 2x10−16; Bonferroni-adjusted Pairwise Wilcoxon Rank Sum C. remanei:C. elegans
p = 1, C. remanei:C. briggsae
p < 2x10−16; C. briggsae:C.elegans
p < 1.5x10−11) and X chromosome (Kruskal-Wallis χ
2 = 40.36; df = 2, p < 1.7x10−9; Bonferroni-adjusted Pairwise Wilcoxon Rank Sum C. remanei:C. elegans
p = 0.92, C. remanei:C. briggsae
p < 4x10−9; C. briggsae:C.elegans
p < 2x10−5).