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Background China is an important biogeographical zone in which the genetic legacies of the Tertiary and Quaternary periods are abundant, and the contemporary geography environment plays an important role in species distribution. Therefore, many biogeographical studies have focused on the organisms of the region, especially zooplankton, which is essential in the formation of biogeographical principles. Moreover, the generality of endemism also reinforces the need for detailed regional studies of zooplankton. Bosmina , a group of cosmopolitan zooplankton, is difficult to identify by morphology, and no genetic data are available to date to assess this species complex in China. In this study, 48 waterbodies were sampled covering a large geographical and ecological range in China, the goal of this research is to explore the species distribution of Bosmina across China and to reveal the genetic information of this species complex, based on two genetic markers (a mtDNA 16S and a nuclear ITS). The diversity of taxa in the Bosmina across China was investigated using molecular tools for the first time. Results Two main species were detected in 35 waterbodies: an endemic east Asia B. fatalis , and the B. longirostris that has a Holarctic distribution. B. fatalis had lower genetic polymorphism and population differentiation than B. longirostris. B. fatalis was preponderant in central and eastern China, whereas B. longirostris was dominated in western China. The third lineage ( B. hagmanni ) was only detected in a reservoir (CJR) of eastern China (Guangdong province). Bosmina had limited distribution on the Tibetan plateau. Conclusions This study revealed that the biogeography of Bosmina appear to be affected by historical events (Pleistocene glaciations) and contemporary environment (such as altitude, eutrophication and isolated habitat). Electronic supplementary material The online version of this article (10.1186/s12862-019-1474-4) contains supplementary material, which is available to authorized users.

It has been reported that community structure of crustacean zooplankton is related to environment factors and abundance of predacious fishes. Most studies, however were based on observation on independent water bodies, which may complicate the results with uninterested factors. A large river-connected lake has partitioned regions with the characteristics of either a river or a lake albeit allowing exchanging of zooplankton of different regions. Thus, a river-connected lake is an ideal system for studying distribution of crustacean zooplankton and investigating its affecting factors. In this study, 11 stations of a large river-connected lake, Lake Gaoyou, were sampled in all four seasons. Taxonomic diversity and species abundance were recorded and their correlation with environmental factors was investigated. A total of 26 and 22 species of crustacean zooplankton were recorded in the river and lake region, respectively. The abundance of crustacean in the river region was significantly higher than that in the lake region. The relative abundance of calanoids and Bosmina fatalis in the river region was lower than that in the lake region, whereas the abundance of cyclopoids and other cladocera species was lower in the lake region than in the river region. Cluster analysis showed that crustacean assemblages could be divided into two, one cluster grouping all sites from the river region, and the other cluster included all sites in the lake region. According to Pearson correlation and canonical correspondence analysis, the distribution of crustacean was positively correlated with water temperature and chlorophyll a gradient. Chlorophyll a and fish abundance are excellent predictors on spatial distribution of crustacean zooplankton in Lake Gaoyou. Our findings may also help in planning of bighead carp stocking in Lake Gaoyou.

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The relationship between crustacean zooplankton community and environmental factors remains a hot topic in eutrophication bio-monitoring subject. Most water bodies in the Yangtze River delta are mesotrophic/eutrophic, which has attracted much attention from ecologists. Nevertheless, previous studies on crustacean zooplankton community in this region only focused on their relation to physicochemical factors excluding phytoplankton. In this study, the crustacean zooplankton abundance and environmental factors (physicochemical factors and phytoplankton abundance) were investigated in Spring, Summer, Autumn and Winter in 13 waterbodies (8 lakes and 5 reservoirs) located in the Yangtze River delta. Results showed that NO2−–N and TN in Spring, SD and TP in Summer had significant difference (P < 0.05) between 8 lakes and 5 reservoirs. That may be related to microbial communities and macrophytes. All 13 studied water bodies were dominated by cyanophyta, whose Microcystis may determine the dominance of Bosmina fatalis. Moreover, eutrophic level should be in relation to the significant difference of plankton between 8 lakes and 5 reservoirs. Finally, five factors (cyanophyta, SD, WT, pH and DO) were significantly correlated with crustacean zooplankton abundance. That indicated the metabolism, reproduction, development and competitors of crustacean zooplankton were affected by these five factors. This research provided basic data of the 13 water bodies and studied the relationship between zooplankton and physicochemical factors as well as phytoplankton, providing scientific basis for the monitoring of eutrophic waterbodies located in the Yangtze river delta.