Gene and Genome Duplication in Spiders.

Gene and genome duplications are widely observed across various organisms, including plants, yeasts, and animals. Numerous studies link gene duplications to the emergence of novel phenotypes, supporting the hypothesis that duplication events are advantageous for adaptive evolution. Whole-genome duplications (WGD) are especially prevalent in plants and have also occurred ancestrally in vertebrates. However, large-scale duplication events in other animal groups remain understudied, partly due to limited genomic resources. Arthropods, particularly insects, represent one of the most diverse animal clades in terms of both species and phenotypic diversity. With increasing availability of chromosome-level genomes, large-scale duplications appear to be rare in insects but are more frequent in chelicerates (e.g. spiders, scorpions, and horseshoe crabs). This makes chelicerates an intriguing group for comparing the mechanisms, fates, and evolutionary impacts of large-scale duplications with those seen in plants and vertebrates. In this review, we synthesize and discuss current research on WGD in spiders and discuss different scenarios for genes following gene duplication events (conservation, nonfunctionalization, subfunctionalization, specialization, drift, neofunctionalization) in the context of experimental studies. We hypothesize if there might be common trajectories after duplication and how these could be tested.