Integrative taxonomy of giant crested Eusirus in the Southern Ocean, including the description of a new species (Crustacea: Amphipoda: Eusiridae)

Among Antarctic amphipods of the genus Eusirus, a highly distinctive clade of giant species is characterized by a dorsal, blade-shaped tooth on pereionites 5–7 and pleonites 1–3. This lineage, herein named ‘crested Eusirus’, includes two potential species complexes, the Eusirus perdentatus and Eusirus giganteus complexes, in addition to the more distinctive Eusirus propeperdentatus. Molecular phylogenies and statistical parsimony networks (COI, CytB and ITS2)of crested Eusirus are herein reconstructed. This study aims to formally revise species diversity within crested Eusirus by applying several species delimitation methods (Bayesian implementation of the Poisson tree processes model, general mixed Yule coalescent, multi-rate Poisson tree processes and automatic barcode gap discovery) on the resulting phylogenies. In addition, results from the DNA-based methods are benchmarked against a detailed morphological analysis of all available specimens of the E. perdentatus complex. Our results indicate that species diversity of crested Eusirus is underestimated. Overall, DNA-based methods suggest that the E. perdentatus complex is composed of three putative species and that the E. giganteus complex includes four or five putative species. The morphological analysis of available specimens from the E. perdentatus complex corroborates molecular results by identifying two differentiable species, the genuine E. perdentatus and a new species, herein described as Eusirus pontomedon sp. nov. ADDITIONAL KEYWORDS: alpha taxonomy – cryptic species – genetics – molecular systematics – phylogenetic systematics.

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phylogenetic tree, EVOLUTION, systematic, systematics, Phylogenetics, taxinomie, Genetic Speciation, morphology, Genetic, new name, biodiversity., COI, Glacial, species, taxonomie, taxonomy, species diagnostic, zoogeography, type locality, Biological Evolution, new taxa, Crustacea, speciation., Phylogeny, DNA barcoding, species groups and keys, type designation, révision, nouvelles espèces, Biogeography, molecular evolution; phylogenetic trees; substitution models; among-site rate variation, Biodiversity, DNA, new records, (14) zoologie, phylogenetic analyses, synonyms, mtDNA, molecular phylogeny, phylogeography, Phylogeography, new species, benthic invertebrates, Crustacea: genetics, types., Biological, Evolutionary Biology, biodiveristy, types, mtdna sequences, Atlantic Ocean, species nova, species diversity, biodiversity, nova species, synonymy, Taxonomy, new synonymy, n.sp., DNA, Mitochondrial, Cryptic species, Antarctica, taxonomic revision, Speciation, phylogeny, Antarctic, valid names, benthos

Research Themes: Antarctica, Crustacea, Phylogeny and Systematics