Fig. 4

Intra-species and inter-species copy number variation (CNV) in gene families involved in freezing avoidance (A,B) and glacier-paced expansion of ZPAX1 and ZPC5 (C,D). A The relative copy number abundance of ZPAX1, ZPC5, and AFGP in the C. hamatus populations using two single-copy genes atraid, rgs20 as controls. *P < 0.05, **P < 0.01 (Kruskal-Wallis rank sum test). B ZPAX1 and ZPC5 CNV in notothenioid species. C,D The periodic distribution of dS values of the ZPAX1 (C) and ZPC5 (D) gene families. The smooth line is the dS density curve indicating the periodic distribution of the dS values of the two gene families in Antarctic notothenioids. The inset image in C and D is the distribution of dS and dN obtained from the C. aceratus ZPAX1 and ZPC5 gene sets respectively. The dS values were translated into the divergence time and overlayed with the δ¹⁸O fluctuation curve of Lisckiecki and Raymo [64]. Noting that the scales of y-axis in the δ¹⁸O curve are reversed