Notes on Indian wolf spiders: IV. Transfer of species previously included in the genera Crocodilosa Caporiacco, 1947 and Geolycosa Montgomery, 1904 (Araneae: Lycosidae)

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  Notes on Indian wolf spiders: IV. Transfer of species previously included in the genera Crocodilosa Caporiacco, 1947 and Geolycosa Montgomery, 1904 (Araneae: Lycosidae) The enigmatic Crocodilosa Caporiacco, 1947 sensu lato currently consists of five nominal species distributed in Africa and Asia (World Spider Catalog 2026). It was established for C. kittenbergeri Caporiacco, 1947, with a superficial generic diagnosis relying only on somatic features such as length of eye rows, leg spination and relative leg lengths (Caporiacco 1947). Roewer (1955), following Caporiacco’s (1947) generic diagnosis, drastically increased the number of Crocodilosa species by transferring several species from other lycosid genera, but most of these subsequently added species were later reassigned to their appropriate genera (World Spider Catalog 2026), highlighting the need for a re-examination of the type species and remaining congeners to clarify the validity of Crocodilosa. At present, the genus ha...

A comprehensive examination of Chelicerate genomes reveals no evidence for a whole genome duplication among spiders and scorpions

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A comprehensive examination of Chelicerate genomes reveals no evidence for a whole genome duplication among spiders and scorpions

Abstract


Whole genome duplications (WGDs) can be a key event in evolution, playing a role in both adaptation and speciation. While WGDs are common throughout the history of plants, only a few examples have been proposed in metazoans. Among these, recent proposals of WGD events in Chelicerates, the group of Arthropods that includes horseshoe crabs, ticks, scorpions, and spiders, include several rounds in the history of horseshoe crabs, with an additional WGD proposed in the ancestor of spiders and scorpions. However, many of these inferences are based on evidence from only a small portion of the genome (in particular, the Hox gene cluster); therefore, genome-wide inferences with broader species sampling may give a clearer picture of WGDs in this clade. Here, we investigate signals of WGD in Chelicerates using whole genomes from 17 species. We employ multiple methods to look for these signals, including gene tree analysis of thousands of gene families, comparisons of synteny, and signals of divergence among within-species paralogs. We test several scenarios of WGD in Chelicerates using multiple species trees as a backbone for all hypotheses. While we do find support for at least one WGD in the ancestral horseshoe crab lineage, we find no evidence for a WGD in the history of spiders and scorpions using any genome-scale method. This study not only sheds light on genome evolution and phylogenetics within Chelicerates, but also demonstrates how a combination of comparative methods can be used to investigate signals of ancient WGDs.

A comprehensive examination of Chelicerate genomes reveals no evidence for a whole genome duplication among spiders and scorpions Gregg W.C. Thomas, Michael T.W. McKibben, Matthew W. Hahn, Michael S. Barker bioRxiv 2024.02.05.578966; doi: https://doi.org/10.1101/2024.02.05.578966