The eastern Palaearctic is a centre of diversity for freshwater cladocerans (Crustacea), but little is known about the evolution and taxonomy of this diversity. Daphnia curvirostris is a Holarctic species complex that has most of its diversity in the eastern Palaearctic. We examined the phylogeography, rates of evolution and taxonomic status for each clade of the D. curvirostris complex using morphological and genetic evidence from four genes. The cybertaxonomical and morphological evidence supported an eastern Palaearctic clade, with at least four species (described here as the Daphnia korovchinskyi sp. nov. group) having diagnostic morphological characters. We also detected convergent morphological characters in the D. curvirostris complex that provided information about species boundaries. Two of the new species (Daphnia koreana sp. nov. and Daphnia ishidai sp. nov.) are known from single ponds and are threatened by human activity. Divergence time estimates suggested an ancient origin (12–28 Mya) for the D. korovchinskyi group, but these estimates are complicated by the small number of calibration points.
Cladocerans (Crustacea: Branchiopoda) of Northern Eurasia traditionally belong to the most intensively studied groups of freshwater microcrustaceans. However, despite a significant progress in our knowledge of different aspects on their biology, some intriguing questions remain unresolved. The hypothesis of cladoceran faunas differentiation between the western and eastern parts of Northern Eurasia agrees with the continental endemism concept. But to date few cladoceran species groups have been investigated through the whole North Eurasian range. Our current work contributes to the confirmation of this hypothesis through a revision of the poorly studied Pleuroxus trigonellus species group. Based on material from Europe, we redescibed morphology of Pleuroxus trigonellus (O.F. Müller, 1776) s.str. and found that its distribution range is potentially restricted to the western portion of Northern Eurasia. At the same time, morphologically similar populations from the eastern portion of Eurasia belong to a new species, Pleuroxus yakutensis sp. nov. These two species are basically similar in general morphology of parthenogenetic and gamogenetic females, but have clear differences in the male morphology. Additionally we offer an identification key for discrimination of the P. trigonellus group from P. uncinatus (Baird, 1850) according to morphological features of the males.
Water fleas (Crustacea: Cladocera) of the Family Bosminidae have been studied since the founding of paleolimnology and freshwater ecology. However, one species, Bosminopsis deitersi, stands out for its exceptional multicontinental range and broad ecological requirements. Here we use an integrated morphological and multilocus genetic approach to address the species problem in B. deitersi. We analyzed 32 populations of B. deitersi s. lat. Two nuclear and two mitochondrial loci were used to carry out the bGMYC, mPTP and STACEY algorithms for species delimitation. Detailed morphological study was also carried out across continents. The evidence indicated a widely distributed cryptic species in the Old World (Bosminopsis zernowi) that is genetically divergent from B. deitersi s.str. We revised the taxonomy and redescribed the species in this complex. Our sampling indicated that B. zernowi had weak genetic differentiation across its range. A molecular clock and biogeographic analysis with fossil calibrations suggested a Mesozoic origin for the Bosminopsis deitersi group. Our evidence rejects the single species hypothesis for B. deitersi and is consistent with an ancient species group (potentially Mesozoic) that shows marked morphological conservation. The family Bosminidae, then, has examples of both rapid morphological evolution (Holocene Bosmina), and morphological stasis (Bosminopsis).
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