Phylogenomics, diversi?cation dynamics, and comparative transcriptomics across the spider tree of life

Dating back to almost 400 mya, spiders are among the most diverse terrestrial predators [1]. However, despite considerable effort [1–9], their phylogenetic relationships and diversi?cation dynamics remain poorly understood. Here, we use a synergistic approach to study spider evolution through phylo-genomics, comparative transcriptomics, and line-age diversi?cation analyses. Our analyses, based on ca. 2,500 genes from 159 spider species, reject a single origin of the orb web (the ‘‘ancient orb-web hypothesis’’) and suggest that orb webs evolved multiple times since the late Triassic–Jurassic. We ?nd no signi?cant association between the loss of foraging webs and increases in diversi?cation rates, suggesting that other factors (e.g., habitat heterogeneity or biotic interactions) potentially played a key role in spider diversi?cation. Finally, we report notable genomic differences in the main spider lineages: while araneoids (ecribellate orb-weavers and their allies) reveal an enrichment in genes related to behavior and sensory reception, the retrolateral tibial apophysis (RTA) clade—the most diverse araneomorph spider lineage—shows enrichment in genes related to immune responses and polyphenic determination. This study, one of the largest invertebrate phylogenomic analyses to date, highlights the usefulness of transcriptomic data not only to build a robust backbone for the Spider Tree of Life, but also to address the genetic basis of diversi?cation in the spider evolutionary chronicle.