Phylogenomics resolves a spider backbone phylogeny and rejects a prevailing paradigm for orb web evolution.

Area of Science:

• Arachnology
• Evolutionary Biology
• Genomics

Background:

• Spiders are ancient predators with vital ecological roles.
• Their evolutionary relationships and the origin of key traits like silk are poorly understood.
• Existing phylogenetic hypotheses often lack robust molecular support.

Purpose of the Study:

• To reconstruct a robust phylogeny for major spider lineages using phylogenomics.
• To test existing hypotheses regarding the monophyly of Orbiculariae (orb-weaving spiders).
• To investigate the evolutionary origins of the orb web.

Main Methods:

• Phylogenomic analysis incorporating taxa from all major spider lineages.
• Utilized comprehensive molecular data to resolve deeper-level phylogenetic relationships.
• Compared results with existing morphological and molecular hypotheses.

Main Results:

• A robust spider phylogeny was recovered, confirming some established clades.
• The monophyly of Orbiculariae was rejected, challenging the prevailing paradigm.
• Cribellate deinopoid orb weavers were found to be more closely related to webless spiders than to araneoid orb weavers.

Conclusions:

• Spider phylogeny requires significant revision, particularly concerning orb-weaving lineages.
• The evolution of the orb web is re-evaluated, suggesting either an earlier origin or multiple independent evolutions.
• These findings impact our understanding of spider evolution, biomaterials, and web construction.