A new study challenges traditional views on arachnid evolution, suggesting that the transition from water to land occurred multiple times rather than in a single event. The research also highlights the role of whole-genome duplication in shaping key traits in spiders and scorpions, such as silk production and venom synthesis. These findings offer new insights into chelicerate phylogeny and provide a foundation for future genetic and evolutionary studies.

[Hebrew University of Jerusalem]– A new review paper by Dr. Efrat Gavish-Regev from The National Natural History Collections at The Hebrew University of Jerusalem and Professor Prashant P. Sharma from the Department of Integrative Biology and Zoological Museum at the University of Wisconsin provides an updated perspective on the evolutionary history of chelicerates- a diverse and ecologically significant group of arthropods that includes spiders, scorpions, mites, and horseshoe crabs.

Published in the Annual Review of Entomology, the review examines how advances in molecular phylogenetics, evolutionary developmental biology, and genomic research have reshaped our understanding of chelicerate evolution. Traditionally, arachnids were considered a terrestrial monophyletic group—meaning they descended from a single colonization event of land by a terrestrial ancestor. However, recent phylogenomic studies challenge this view, indicating that horseshoe crabs are nested within the arachnids rather than forming a separate, sister lineage. This suggests that arachnids may have colonized land multiple times rather than through a single evolutionary event.

“The idea that all arachnids share a single terrestrial ancestor has been widely accepted for decades, but the latest molecular evidence and a different interposition of some homologies points to a more complex scenario,” says Dr. Gavish-Regev. “Instead of a straightforward transition from water to land, our research suggests that different arachnid groups may have independently adapted to terrestrial life at different points in their evolutionary history.”

One of the key findings of the study is the role of whole-genome duplications in chelicerate evolution. These events, which resulted in the duplication of entire genomes, have been identified in spiders and scorpions and may have contributed to the diversification of these groups by enabling the evolution of new biological functions, including silk production and venom synthesis.

“Arachnoid evolution has been shaped by a number of factors, including gene duplications that likely played a role in the development of key traits,” explains Prof. Sharma. “By combining phylogenetic research with new gene-editing tools, we are now in a position to explore these evolutionary changes in greater detail than ever before.”

The study also highlights new developments in the study of chelicerate phylogeny, including the application of advanced genomic techniques to resolve long-standing questions about interrelationships within the group. While some evolutionary relationships remain unresolved, the increasing availability of high-quality genomic data is expected to provide further clarity in the coming years.

The findings have broad implications for evolutionary biology, shedding light on the mechanisms that drive biodiversity and adaptation in arthropods. Beyond fundamental research, understanding chelicerate evolution can also have practical applications in areas such as pest management, biomedicine, and bio-inspired materials.