Abstract
Water fleas (Crustacea: Cladocera) are among the most intensively studied freshwater invertebrates. However, ecologically important daphniids that live on the surface layer (neuston) remain taxonomically confused. Here we attempt to reconcile genetic and morphological information for the neustonic genus Scapholeberis Schoedler, 1858 (Cladocera: Daphniidae) and present the first revision of the Scapholeberis kingii species group. We analyzed new and existing mitochondrial DNA sequences (сytochrome C oxidase subunit I gene region) together with morphology for all but one of the known species of the neustonic daphniids. Morphological comparisons of available populations, belonging to the Scapholeberis kingii species group from several Australian, Asian and African localities, revealed, that they are almost identical according to parthenogenetic females. However, Australian populations can be reliably distinguished from Asian ones based on the morphology of gamogenetic females. Mitochondrial DNA data analyses revealed divergent lineages (>17% for the DNA barcoding COI region) for the three different species (Australia, Asia and Africa). Based on this set of data, we redescribed S. kingii Sars, 1888 from Australia, its terra typica, and described a new species, S. smirnovi sp.nov. from the Russian Far East, Korea and Japan. The status of populations from Ethiopia and the Republic of South Africa remained unclear, because in the African material and the putative type material, we found only parthenogenetic females. Our results provide an integrative revision of the S. kingii species group and improve the taxonomic scaffold used for barcoding and genomics for the remaining species groups in the daphniid genus Scapholeberis.
Highlights
Integrative taxonomy combines the evidence from disparate biological disciplines to better understand biodiversity
Sampling in Ethiopia was conducted in frames of work of the Joint Ethiopian-Russian Biological Expedition (JERBE), with permission from the Ministry of Environment of Ethiopia to JERBE
Deep branches within Scapholeberis had low to moderate support in the Maximum Likelihood (ML) tree
Summary
Integrative taxonomy combines the evidence from disparate biological disciplines to better understand biodiversity. This approach has been fruitful for taxonomically challenging yet well-studied aquatic groups such as the water fleas. The sexual stages appear sporadically, but can be a rich source of diagnostic morphological characters (see review in Kotov, 2013). Genetic approaches, such as formal genetic barcoding (Hebert et al, 2003), have much value for the discovery of novel lineages and taxonomic diagnoses. As museum samples, including type materials, are generally not amenable to genetic study (but see Umetsu et al, 2002; Turko et al, 2019), taxonomic advances are often limited to morphological evidence
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