Fig. 2

The expression patterns between the spider venom glands and other tissues across multiple species. a PCA using the expression levels of 1983 orthologs from ten species. The shapes and colors of the points represent species and tissues, respectively. The red dotted circles represent the clustering of glandular tissues. b PCA of the 2388 ortholog expression matrix across six species in the dotted box. c PCA of the 3952 ortholog expression matrix across four species, whose branches are shown in light blue. d Module preservation between the common house spider venom glands and other tissues. Z_summary > 10 implies strong preservation; Z_summary values between 2 and 10 indicate weak to moderate evidence of preservation; if Z_summary < 2, there is no evidence that the module is preserved. The red dot (module 1) represents the core network. e The observed pairwise semantic similarity (SS) scores and permutated ones between the common house spider venom glands and other tissues. Of these, the fifth density plot represents the high similarity between the spider ovary and fruit fly ovary (this value was used as a control in our analysis). The vertical lines show the observed pairwise SS values. The shades show 1000 permutated SS values with 95th and 90th percentiles labeled. f Workflow for similarity index (SI) calculations among the DUGs of glandular tissues. See the “Methods” section for the meaning of the equation. SI, similarity index; DUGs, differentially upregulated genes. g SI comparisons among the DUGs of the common house spider venom glands and glandular tissues. The comparison result between the spider ovary and fruit fly ovary is labeled in blue, showing high similarity (this value was also introduced as a control). The dotted line in the violin plot represents the median value. **FDR < 0.01 (Mann‒Whitney U test). See Additional file 2: Fig. S7–S10 for other comparison results