Fig. 7.

Data sets from two snake families show that more abundant venom proteins evolve more rapidly. Both panels show evolutionary rates, averaged by toxin class, as a function of abundance, using data from five crotaline species in three Old and New World genera (a), and the king cobra genome (re-analyzed from Fig. 5 in Vonk et al. [43]) (b). These results mirror the pairwise differences between P. elegans and P. flavoviridis shown in Fig. 6. In both cases, average evolutionary rates for the most abundant toxin classes tend to lie above dN/dS > 1, suggesting positive selection. Analyses for the two families are presented separately, because they vary greatly in toxin class composition and relative abundance of venom constituents. Significance of the associations was computed using Spearman’s rank correlation. Abbreviations: 3FTX: 3-finger toxins, APA: Aminopeptidase A, BPP: bradykinin-potentiating peptide, GBL: galactose-binding lectin, CRISP: cysteine-rich secretory proteins, DPP: dipeptidylpeptidase IV, HYAL: hyaluronidase, NGF: nerve growth factor, VEGF: vascular endothelial growth factor (see additional abbreviations in Fig. 6)