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There is increasing interest in the diversity and phylogeography of aquatic invertebrate zooplankton in the Eastern Palearctic, yet this topic remains largely unexplored in China. Here, we investigated the lineage diversity and phylogeography of an important cladoceran taxon, the Scapholeberis kingii (Cladocera: Daphniidae) species complex, members of which live in the surface layers of freshwater ecosystems. We identified only the S. smirnovi morphospecies from this species complex in 29 of 491 Chinese water bodies examined. Its phylogenetic position was verified using both a mitochondrial (mitochondrial cytochrome c oxidase subunit I; COI) and a nuclear marker (the nuclear large subunit ribosomal RNA gene; 28S). Pronounced geographical separation among three S. smirnovi mitochondrial lineages was observed in China: only a single lineage (Lineage A) was present in the Eastern Plain, whereas Lineages B and C were restricted to the Inner Mongolia-Xinjiang Plateau and the Qinghai-Tibetan Plateau respectively. This deep mtDNA divergence and the substantial genetic differentiation among S. smirnovi populations from different regions is likely a result of the rapid uplift of the Qinghai-Tibetan Plateau and associated ecological changes. This study contributes to an understanding of the genetic diversity of the S. kingii complex, a key component of neustonic zooplankton., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

The distribution and species/lineage diversity of freshwater invertebrate zooplankton remains understudied in China. Here, we explored the species/lineage diversity and phylogeography of Ceriodaphnia species across China. The taxonomy of this genus is under-explored. Seven morphospecies of Ceriodaphnia (C. cornuta, C. laticaudata, C. megops, C. pulchella, C. quadrangula, C. rotunda and C. spinata) were identified across 45 of 422 water bodies examined. Rather little morphological variation was observed within any single morphospecies regardless of country of origin. Nevertheless, we recognized that some or all of these morphospecies might represent species complexes. To investigate this, phylogenetic relationships within and among these morphospecies were investigated based on mitochondrial (partial cytochrome c oxidase subunit I gene) and nuclear (partial 28S rRNA gene) markers. The mitochondrial marker placed these populations in nine lineages corresponding to the morphospecies: C. laticaudata and C. pulchella were each represented by two lineages, suggesting that both are species complexes. The remaining five morphospecies were each represented by a single mtDNA lineage. Three of the nine mitochondrial lineages (belonging to C. pulchella, C. rotunda and C. megops) are newly reported and exhibited a restricted distribution within China. The nuclear-DNA phylogeny also recognized seven Ceriodaphnia taxa within China. We detected occasional mito-nuclear discordances in Ceriodaphnia taxa across China, suggesting interspecific introgression and hybridization. Our study contributes to an understanding of the species/lineage diversity of Ceriodaphnia, a genus with understudied taxonomy., (Copyright © 2022 Elsevier Inc. All rights reserved.)

The distribution and genetic diversity of freshwater zooplankton is understudied in the Eastern Palearctic. Here, we explored the lineage diversity and regional distribution of the genus Moina in China. Members of this genus are often keystone components of freshwater ecosystems and have been frequently subjected to toxicological and physiological studies. Four species of Moina were identified, based on morphology, in 50 of 113 Chinese water bodies examined, and their phylogenetic position was analyzed using both a mitochondrial (mitochondrial cytochrome c oxidase subunit I; COI) and a nuclear marker (the nuclear internal transcribed spacer; ITS-1). Both molecular markers identified four clades corresponding broadly to the morphological species. Mitochondrial DNA analysis showed the presence of four species complexes with eleven lineages across China, five of which were new. However, some lineages (and even individual haplotypes) were widespread in Eurasia, suggesting an ability to disperse over long distances. In contrast, a few lineages exhibited restricted distributions. The nuclear phylogeny also recognized four species of Moina within China and seven very distinct clades. Interestingly, one specimen possessing Moina cf. micrura mtDNA had ITS-1 alleles of the M. cf. brachiata clade. This discordance between mtDNA and nuclear ITS-1 phylogenies is indicative of interspecific introgression and hybridization. Additionally, our COI phylogeny showed apparent paraphyly in two Moina species groups, suggesting introgression of their mitochondrial genomes. Our data shows the regional distribution/diversity of the Moina species complex in a Eurasian context., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Cladocerans are well-studied planktonic crustaceans, especially those of the genus Daphnia in which interesting evolutionary questions have been addressed on speciation processes. The aim of the present study is to demonstrate that other genera of cladocerans show similar levels of cryptic diversity, intraspecific gene flow, and thus become useful model systems for comparison. In order to do so, we chose the genus Diaphanosoma, widespread in tropical and temperate areas. We started with a survey of species diversity in the genus Diaphanosoma in Asia using a morphological approach, then obtained sequences from a mitochondrial and a nuclear marker from multiple individuals of different species, performed tests on DNA taxonomy and molecular phylogenies, and assessed the role of hybridization in explaining the cases of mitonuclear discordance. The results are that cryptic diversity occurs in Diaphanosoma, and mitonuclear discordance was found in about 6% of the sequenced animals. Past hybridization is supported as the most likely explanation for the discordance: no evidence was found of first generation hybrids with heterozygous sequences. Our analysis on patterns of genetic diversity in Diaphanosoma supports similarities and differences with what is known in Daphnia., (Copyright © 2017 Elsevier Inc. All rights reserved.)

The cosmopolitanism paradigm in the biogeography of freshwater invertebrates is currently being replaced by non-cosmopolitanism or continental endemism. Benthic water fleas (Cladocera) from the family Chydoridae were the first group of freshwater invertebrates for which non-cosmopolitanism and cryptic diversity was substantiated by morphological studies. Yet, little is known about genetic differentiation and evolutionary history of chydorid species complexes. Here we present the first analysis of the genetic versus morphological differentiation in a benthic cladoceran species complex-Chydorus sphaericus s. str. using sequence variation in a nuclear (ribosomal internal transcribed spacer 2, ITS-2) and a mitochondrial (cytochrome c oxidase subunit I, COI) genes in 50 Holarctic localities. We tested for continental endemism and cryptic diversity predicted by previous morphological studies. We found evidence for the presence of at least seven putative regional species in the Holarctic, at least three of them being distributed beyond a single continent. While the molecular and sexual stage characters showed general concordance on species lineages, parthenogenetic female characters lacked resolution or were unassociated with molecular lineages. We conclude that cryptic regional lineages of benthic cladocerans are apparent and that the sexual stages represent the most informative morphological source of species characters for this environmental indicator group.