Extant primitively segmented spiders have recently diversified from an ancient lineage

Area of Science:

• Evolutionary Biology
• Zoology
• Phylogenetics

Background:

• Living fossils are lineages retaining ancestral traits over long periods, often expected to have ancient origins and diversification.
• Recent studies challenge this notion in some classic living fossil examples like cycads and coelacanths.
• Liphistiid spiders, grouped in Mesothelae, are considered living fossils due to retained plesiomorphic traits.

Purpose of the Study:

• To investigate the origin and diversification patterns of liphistiid spiders using a phylogenetic approach.
• To reconstruct the biogeographic history of liphistiids by providing a robust phylogenetic framework.
• To test whether liphistiid spiders conform to the traditional living fossil model of ancient origin and diversification.

Main Methods:

• Phylogenetic analyses were conducted using original sampling across the Asian range of liphistiids.
• Dating analyses were employed to estimate divergence times.
• Biogeographic history was reconstructed based on the phylogenetic framework and fossil evidence.

Main Results:

• Phylogenetic analyses confirmed the monophyly of the family Liphistiidae and its eight genera.
• Dating analyses suggest an eastward, over-land dispersal from a Carboniferous Euramerican origin of Mesothelae to the Asian origin of Liphistiidae during the Palaeogene (39-58 Ma).
• Diversification within extant liphistiid genera is relatively recent, occurring in the Neogene and Late Palaeogene (4-24 Ma), contrary to expectations for living fossils.

Conclusions:

• The evolutionary history of liphistiid spiders, including their ancient origin and recent diversification, challenges traditional living fossil paradigms.
• The findings support an over-land dispersal model for their biogeographic history, with no over-water dispersal events required.
• Liphistiid spider evolutionary history offers significant insights for vicariant biogeography studies.