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Rivers suffer from multiple stressors acting simultaneously on their biota, but the consequences are poorly quantified at the global scale. We evaluated the biological condition of rivers globally, including the largest proportion of countries from the Global South published to date. We gathered macroinvertebrate- and fish-based assessments from 72,275 and 37,676 sites, respectively, from 64 study regions across six continents and 45 nations. Because assessments were based on differing methods, different systems were consolidated into a 3-class system: Good, Impaired, or Severely Impaired, following common guidelines. The proportion of sites in each class by study area was calculated and each region was assigned a Köppen-Geiger climate type, Human Footprint score (addressing landscape alterations), Human Development Index (HDI) score (addressing social welfare), % rivers with good ambient water quality, % protected freshwater key biodiversity areas; and % of forest area net change rate. We found that 50% of macroinvertebrate sites and 42% of fish sites were in Good condition, whereas 21% and 29% were Severely Impaired, respectively. The poorest biological conditions occurred in Arid and Equatorial climates and the best conditions occurred in Snow climates. Severely Impaired conditions were associated (Pearson correlation coefficient) with higher HDI scores, poorer physico-chemical water quality, and lower proportions of protected freshwater areas. Good biological conditions were associated with good water quality and increased forested areas. It is essential to implement statutory bioassessment programs in Asian, African, and South American countries, and continue them in Oceania, Europe, and North America. There is a need to invest in assessments based on fish, as there is less information globally and fish were strong indicators of degradation. Our study highlights a need to increase the extent and number of protected river catchments, preserve and restore natural forested areas in the catchments, treat wastewater discharges, and improve river connectivity.

Species of the genus Himalopsyche (Trichoptera, Rhyacophilidae) inhabit alpine to montane environments in Central and East Asia and North America. Diversity of the genus is concentrated primarily in the Himalayas and surrounding mountain ranges. Phylogenetic hypotheses have hitherto been proposed based on morphological data. Here, we present the first molecular phylogeny of Himalopsyche based on six gene fragments, using three methods of phylogenetic inference. Based on the phylogenetic analyses, we re-evaluated species groups suggested by previous authors based on adult male morphology. We found that the previously defined groups are largely supported by molecular evidence as well as larval and adult morphology. However, we modify the species groups so that Himalopsyche phryganea and Himalopsyche lepcha constitute monotypic groups, and so that the tibetana group and anomala group sensu Schmid & Botosaneanu are merged to a single group, here defined as the tibetana group. Thus, we propose that Himalopsyche can be divided into five groups: kuldschensis group, lepcha group, navasi group, phryganea group, and tibetana group. We also provide a biogeographic synthesis of Himalopsyche distributions.

Summary Ecological studies of freshwater biota in understudied regions are often obstructed by poor taxonomic knowledge. We posit that molecular tools can help alleviate this issue and present an example where we combined molecular tools, environmental data and ecological statistics to investigate the distribution and community ecology of an unknown fauna of hydropsychid caddisflies along altitudinal gradients in four Himalayan river systems of Central and Eastern Nepal. A total of 484 larval specimens from 34 tributaries were examined. Phylogenetic analysis of the mitochondrial cytochrome c oxidase I (COI) and the nuclear ribosomal RNA 28S were used to delineate molecular operational taxonomic units (MOTUs) applying three analytical methods: general mixed Yule-coalescent (GMYC) model, Automatic Barcode Gap Discovery (ABGD) and Bayesian Phylogenetics and Phylogeography (BPP). Spatial distributional patterns and potential differences in ecological niches among MOTUs were statistically tested using regression and correlation approaches. Further, we examined the data for signs of non-random structure in MOTU communities. MOTU diversity within the family of Hydropsychidae was generally high but varied across evaluated gene fragments and slightly among delineation methods. Yet, the subsequent evaluation of environmental and spatial drivers and resulting distributional patterns were highly consistent among the different MOTU estimates. Within each river system, we found community composition varied greatly along the altitudinal gradients, with many MOTUs associated with specific altitudinal ranges. Prevalent MOTU turnover at the river system scale indicated high β-diversity in the hydropsychid community leading to high degrees of regional endemism. In the Langtang river system, we found fewer MOTU co-occurrences than expected by chance. These results highlight the utility of DNA-based approaches using variable genetic markers (mitochondrial or ribosomal nuclear) for primary biodiversity assessment of poorly studied groups or regions. Our study further shows that DNA-based biodiversity measures are suitable for downstream applications, such as exploring fundamental questions in stream ecology.