Bribiesca Contreras G., Pineda-Enriquez T., Marquez-Borras F., Solis-Marin F.A., Verbruggen H., Hugall A.F. & O'Hara T.
Dark evolutionary offshoot: phylogenomics shed light on the evolutionary history of a new species of cave brittle star
Molecular Phylogenetics and Evolution: submitted


Caves are a useful system for testing evolutionary and biogeographic hypotheses, as they are isolated and their environmental conditions have resulted in adaptive selection across different taxa. In recent years, more cave species have been discovered, even at phyla level, with crustaceans being the most abundant. However, cave-dwelling members of the class Ophiuroidea (brittle stars) are scarce. Out of the almost 2100 species of brittle stars that have been described to date, only two species have been suggested to be true cave-dwellers. These occurrences represent rare colonising events, compared to other groups that are known to have successfully diversified in these systems. A third species from an anchihaline cave system in the Yucatan Peninsula, Mexico has been previously identified from cytochrome oxidase I (COI) barcodes. In this study, we reassess the species boundaries of this putative cave species using a phylogenomic dataset (13 species, 100 exons, 18.7 kbp). We perform species delimitation analyses using robust full-coalescent methods for discovery and validation of hypotheses on species boundaries, as well as infer its phylogenetic relationships with species distributed in adjacent marine regions, in order to investigate the origin of this cave-adapted species. We assess which hypotheses on the origin of subterranean taxa can be applied to this species by taking into account its placement within the genus Ophionereis and its demographic history. We provide a detailed description of Ophionereis commutabilis n. sp., and evaluate its morphological characters in the light of its successful adaptation to life in caves.

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