Molecular evolution analyses of κ- and ω-HXTXs. (A) Evolutionary fingerprint of κ- and ω-HXTXs. Estimates of the distribution of synonymous (α) and non-synonymous (β) substitution rates inferred for the κ-HXTXs, ω-HXTXs, and the combined Shiva superfamily dataset. The ellipses reflect a Gaussian-approximated variance in each individual rate estimate, and colored pixels show the density of the posterior sample of the distribution for a given rate. The diagonal line represents the idealized neutral evolution regime (ω = 1), while points above and below the line correspond to positive selection (ω > 1) and negative selection (ω < 1), respectively. The ω for site model 8, along with the total number of positively selected sites detected by its Bayes Empirical Bayes (BEB) approach and the number of episodically diversifying sites detected by the mixed effects model of evolution (MEME), are also indicated. (B) Molecular evolution of Shiva superfamily toxins from Australian funnel-web spiders. 3D homology models are shown with their molecular surface colored according to the evolutionary conservation of amino acids (see color key); the location of positively selected sites is shown in red in space-fill models and as red spheres in wireframe models. A line plot is also provided to highlight the relative accumulation of dN versus dS, estimated using the M0 model of PAML. NS: Not significant.