Mengyu Lv

Freshwater ecosystems are among the most vulnerable habitats worldwide, and reliable biodiversity assessment is essential for their conservation. Baiyangdian Lake, the largest freshwater lake in northern China, has undergone severe ecological degradation but is now experiencing recovery through restoration efforts. To provide a molecular basis for monitoring biodiversity, we constructed a COI DNA barcode reference library of aquatic insects from Baiyangdian Lake. From January 2023 to May 2025, systematic sampling across representative habitats yielded 315 high-quality sequences covering 104 species, 74 genera, and 33 families within eight insect orders. Diptera, particularly Chironomidae, showed the highest diversity, followed by Odonata. Phylogenetic analysis using maximum likelihood resolved all orders and families as well-supported monophyletic groups, demonstrating strong congruence with morphological taxonomy. Genetic distance analysis revealed a pronounced barcode gap, with mean intraspecific divergence of 0.46% and nearest-neighbor divergence exceeding 15%, confirming the discriminatory power of COI for species identification. Accumulation curves indicated that genus-level diversity is largely captured, while species-level diversity, especially among Diptera, remains incompletely revealed. This study provides the first comprehensive DNA barcode reference library for Baiyangdian aquatic insects, supporting ecological restoration evaluation, eDNA applications, and regional biodiversity conservation strategies.

Baetidae is a globally diverse mayfly family. While COI DNA barcode studies are abundant, its mitogenomic data remain scarce. In this study, we present the first mitochondrial genome of Cloeon viridulum Navás, 1931. The mitogenome of C. viridulum spans 14,431 bp and includes 13 protein-coding genes, 22 transfer RNA genes, and one 16S ribosomal RNA (rRNA) gene. However, it features an incomplete 12S rRNA gene and lacks a control region. This mitogenome has a GC content of 32.4%. Phylogenetic analysis strongly supports a sister relationship between C. viridulum and C. dipterum. Our findings offer genomic insights into Baetidae evolution.

Accurate species identification of small aquatic insects remains challenging due to their morphological similarities. This study addresses this issue by developing a DNA barcode reference library for the globally distributed Brillia (Diptera: Chironomidae). We analyzed cytochrome c oxidase subunit I (COI) sequences of 241 specimens belonging to 13 Brillia species from 18 countries, including 56 newly generated and 185 publicly available COI barcodes. Our integrated approach included genetic distance analysis, haplotype network construction, and ecological niche modeling. The results revealed remarkable cryptic diversity, with sequences clustering into 30 Barcode Index Numbers and 158 unique haplotypes, most being region-specific. Notably, East Asian and North American populations showed complete genetic distinctness, suggesting long-term isolation. Environmental factors, particularly temperature and precipitation gradients, were identified as key drivers of this diversification. The study also corrected several misidentifications in existing databases. These findings significantly advance our understanding of Brillia diversity and provide a reliable molecular tool for freshwater ecosystem monitoring, with important implications for biodiversity conservation and environmental assessment.

Glyptotendipes pallens (Meigen, 1804) serves as a significant bioindicator for monitoring freshwater ecosystems. Despite the performance of COI barcode analyses on G. pallens, the mitogenome of this taxon remains unassembled and unanalyzed. In this study, we provide one newly sequenced complete mitogenome of G. pallens for the first time. The mitogenome is 16,063 bp long with high A + T content, and consists of 13 protein-coding genes, 22 tRNA genes, two rRNA genes, and a noncoding control region. The phylogenetic analysis strongly supports G. pallens and G. tokunagai as sister species.

In the saline water area of our research, deep groundwater was over-pumped for agricultural irrigation which resulted in a decline of the deep groundwater level and an increase in the shallow groundwater table. Soil salination was also aggravated due to the strong evapotranspiration (ET) in the shallow groundwater areas, where ET removes water vapor from the unsaturated zone (ET_u), and the groundwater (ET_g). Joint utilities of multiple water sources of transferred water and local shallow and deep groundwater are essential for reasonable management of irrigation water. However, it is still difficult to distinguish ET_u and ET_g in coupled management of unsaturated zone and groundwater, which account for the water balance in utilities of multiple water sources in a regional scale. In this paper, we used an RS-based ETWatch model as a source of evapotranspiration data coupled with UZF-MODFLOW, an integrated hydrological model of the unsaturated–saturated zone, to estimate the ET_g and ET_u on a regional scale. It was shown that the coupled model (ETWatch-UZF-MODFLOW) avoids the influence of ET_u on the groundwater balance calculation and improves the accuracy of the groundwater model. The model was used in the simulation and prediction of groundwater level. The eastern North China Plain (NCP) was selected as the study area where shallow groundwater was saline water and deep groundwater cone existed. We compared four different scenarios of irrigation methods, including current irrigation scenario, use of saline water, limited deep groundwater pumping, use of multiple water sources of transferred water and local groundwater. Results indicate that the total ET_g for the four scenarios in the study area from 2013 to 2030 is 119 × 10⁸ m³, 81.9 × 10⁸ m³, 85.0 × 10⁸ m³, and 92.3 × 10⁸ m³, respectively, and the proportion of ET_g to total ET was 6.85%, 4.79%, 4.97%, 5.37%. However, in regions where the groundwater depth is less than 3 m, ET_g accounts for 12% of the total ET, indicating that groundwater was one of the main sources of evapotranspiration in shallow groundwater depth area.