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| Ophionereis commutabilis
Bribiesca-Contreras, Pineda-Enríquez, Márquez-Borrás, Solís-Marín, Verbruggen, Hugall & O'Hara, 2019
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Highlights:
• Species delimitation methods and morphology validated a new species of cave brittle star.
• Successful colonisation of anchihaline caves by brittle stars has been very rare.
• The origin of Ophionereis commutabilis does not conform fully to models on the origin of cave taxa.
• Cave brittle stars do not share convergent morphological traits association with cave-life.
Abstract
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. Although in recent years many more cave species have been discovered, cave-dwelling members of the class Ophiuroidea (brittle stars) remain scarce. Out of the more than two thousand species of brittle stars described to date, only three are regarded as 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 (20 specimens in 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.
Keywords: Ophiuroidea, Ophionereis, Anchihaline cave, Multispecies coalescent, Species delimitation
Taxonomy
Family OPHIONEREIDIDAE Ljungman, 1867
Genus Ophionereis Lütken (1859)
Ophionereis commutabilis n. sp.
Etymology: From the feminine Latin adjective commutabilis meaning ‘changeable’ or ‘variable’, in reference to the variable colouration pattern; and ‘adaptable’, as this species successfully adapted to the harsh conditions of an anchihaline cave.
Guadalupe Bribiesca-Contreras, Tania Pineda-Enríquez, Francisco Márquez-Borrás, Francisco A. Solís-Marín, Heroen Verbruggen, Andrew F. Hugall, Timothy D. O'Hara. 2019. Dark Offshoot: Phylogenomic Data Sheds Light on the Evolutionary History of A New Species of Cave Brittle Star. Molecular Phylogenetics and Evolution. 136; 151-163. DOI: 10.1016/j.ympev.2019.04.014
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