Spiders did not repeatedly gain, but repeatedly lost, foraging webs

Area of Science:

• Evolutionary Biology
• Genomics
• Arachnology

Background:

• Recent genomic and transcriptomic data have fueled investigations into spider phylogeny and web evolution.
• Previous studies suggested multiple independent origins of spider webs, including the orb web.
• A specific phylogenetic character coding strategy was employed in prior analyses.

Purpose of the Study:

• To re-evaluate the evolutionary history of spider webs.
• To address methodological issues in previous phylogenetic analyses of spider web origins.
• To determine whether webs are a primitive trait or evolved multiple times.

Main Methods:

• Re-analysis of existing genomic and transcriptomic data on spider phylogeny.
• Correction of phylogenetic character coding for absent traits (webs).
• Addressing issues of taxon name misspellings and natural history inaccuracies.

Main Results:

• Coding absence of webs as inapplicable data, not homologous to present webs, changes evolutionary conclusions.
• Foraging webs are likely primitive for spiders, with an estimated 5-7 losses.
• The orb web may be homologous, with 2-6 instances of secondary loss.

Conclusions:

• Previous conclusions on the numerous de novo origins of spider webs are artifacts of coding strategy.
• Corrected analyses suggest webs are a primitive trait, with multiple losses rather than gains.
• The evolutionary history of spider webs, including the orb web, requires reinterpretation based on accurate data handling.