Hadrurid Scorpion Toxins: Evolutionary Conservation and Selective Pressures

Area of Science:

• Evolutionary biology
• Molecular evolution
• Toxinology

Background:

• Scorpion toxins are believed to originate from housekeeping genes, diversifying through positive selection.
• Understanding toxin evolution is limited by sparse taxonomic sampling, especially in closely related species.
• Phylogenetic inertia has been observed in some scorpion toxins at higher taxonomic levels.

Purpose of the Study:

• To investigate the evolutionary dynamics of toxins in closely related scorpions of the family Hadruridae.
• To assess the incidence and evolutionary patterns of scorpine-like peptides (SLPs) within this family.
• To explore toxin diversity and evolutionary constraints at a shallow taxonomic scale.

Main Methods:

• Utilized new and existing transcriptomic data for phylogenetic and molecular evolutionary analyses.
• Examined evolutionary relationships of scorpions within the Hadruridae family.
• Surveyed the distribution of scorpine-like peptides (potassium channel toxins) and analyzed selection pressures on SLP copies.

Main Results:

• Identified gene duplications in scorpine-like peptides within the studied scorpion taxa.
• Molecular analyses revealed that only eight sites across two SLP copies are under positive selection, with most sites evolving under negative selection.
• Demonstrated evolutionary conservation in toxin diversity among closely related scorpion species.

Conclusions:

• Scorpine-like peptides exhibit gene duplication events.
• Contrary to previous findings, positive selection appears limited in SLPs, with significant negative selection indicating evolutionary constraint.
• Toxin diversity is evolutionarily conserved at shallow taxonomic levels within scorpions.