Freshwater ecosystems are highly biodiverse¹ and important for livelihoods and economic development², but are under substantial stress³. To date, comprehensive global assessments of extinction risk have not included any speciose groups primarily living in freshwaters. Consequently, data from predominantly terrestrial tetrapods^4,5 are used to guide environmental policy⁶ and conservation prioritization⁷, whereas recent proposals for target setting in freshwaters use abiotic factors^8–13. However, there is evidence^14–17 that such data are insufficient to represent the needs of freshwater species and achieve biodiversity goals^18,19. Here we present the results of a multi-taxon global freshwater fauna assessment for The IUCN Red List of Threatened Species covering 23,496 decapod crustaceans, fishes and odonates, finding that one-quarter are threatened with extinction. Prevalent threats include pollution, dams and water extraction, agriculture and invasive species, with overharvesting also driving extinctions. We also examined the degree of surrogacy of both threatened tetrapods and freshwater abiotic factors (water stress and nitrogen) for threatened freshwater species. Threatened tetrapods are good surrogates when prioritizing sites to maximize rarity-weighted richness, but poorer when prioritizing based on the most range-restricted species. However, they are much better surrogates than abiotic factors, which perform worse than random. Thus, although global priority regions identified for tetrapod conservation are broadly reflective of those for freshwater faunas, given differences in key threats and habitats, meeting the needs of tetrapods cannot be assumed sufficient to conserve freshwater species at local scales.

A checklist of the dragonflies and damselflies occurring in Bangladesh, Bhutan, India (including Andaman and Nicobar Islands), Nepal, Pakistan and Sri Lanka is presented. In total 588 (including 559 full species) taxa are known to occur in the region of which 251 taxa (species & subspecies) are single country endemics. Recent taxonomic changes relevant to the area are summarized. Sixteen taxa are synonymized and a checklist of all synonyms established since 1950 is provided. Information is given on available larval descriptions including a list of genera present in the region for which no larvae have yet been described. Numerous species occurring in the area are still poorly known and a list of genera for which a revision is urgently needed is provided. The following new synonyms are established: Calicnemia sudhaae Mitra, 1994 = Calicnemia imitans Lieftinck, 1948 syn. nov.; Ceriagrion fallax cerinomelas Lieftinck, 1927 = Ceriagrion fallax Ris, 1914 syn. nov.; Ceriagrion fallax pendleburyi Laidlaw, 1931 = Ceriagrion fallax Ris, 1914 syn. nov.; Coenagrion kashmirus Chowdhary & Das, 1975 = Ischnura forcipata Morton, 1907 syn. nov.; Enallagma insula Fraser, 1920 = Aciagrion occidentale Laidlaw, 1919 syn. nov.; Himalagrion pithoragarhicum Sahni, 1964 = Ceriagrion fallax Ris, 1914 syn. nov.; Ischnura bhimtalensis Sahni, 1965 = Ischnura rubilio Selys, 1876 syn. nov.; Onychargia indica Sahni, 1964 = Paracercion calamorum (Ris, 1916) syn. nov.; Anaciaeschna kashmirense Singh & Baijal, 1954 = Anaciaeschna martini (Selys, 1897) syn. nov.; Cyclogomphus vesiculosus Selys, 1854 = Cyclogomphus ypsilon Selys, 1954 syn. nov.; Chlorogomphus brittoi Navás, 1934 = Chlorogomphus xanthoptera (Fraser, 1919) syn. nov.; Hylaeothemis indica Fraser, 1946 = Hylaeothemis apicalis Fraser, 1924 syn. nov.; Sympetrum durum Bartenef, 1916 = Sympetrum striolatum commixtum Selys, 1884 syn. nov.; Sympetrum himalayanum Navás, 1934 = Sympetrum hypomelas (Selys, 1884) syn. nov.; Sympetrum haematoneura Fraser, 1924 = Sympetrum speciosum Oguma, 1915 syn. nov.; Sympetrum speciosum taiwanum Asahina, 1951 = Sympetrum speciosum Oguma, 1915 syn. nov. In addition, Periaeschna lebasi Navás, 1930 is regarded a nomen nudum. The following new combinations are proposed: Onychogomphus acinaces Laidlaw, 1922 is transferred to the genus Melligomphus Chao, 1990 resulting in Melligomphus acinaces (Laidlaw, 1922) comb. nov. Onychogomphus saundersii Selys, 1854 is transferred to the genus Nychogomphus Carle, 1986 resulting in Nychogomphus saundersii (Selys, 1854) comb. nov..

Based on a distribution database brought together for the recently published Atlas of the European dragonflies and damselflies, we describe the patterns of diversity and endemism of these insect groups. Highest species richness, as well as richness of predominantly lentic species, occurs in central and western-central Europe. Strictly lotic species have their centre of diversity in southwest France and parts of the Iberian Peninsula. The highest number of endemic species is found in southwest France, the Iberian Peninsula and the Balkan Peninsula. A comparison of the diversity patterns of Odonata species listed in the EU Habitats Directive with those listed in the European Red List highlights a strong mismatch between species threatened in Europe, which are mainly found in the Mediterranean, and species legally protected by the European Union, which are concentrated in central and western Europe. This mismatch has a historical origin, as the species listed in the Habitats Directive were mostly selected in the 1970s and 1980s when water quality in western and central Europe was poor. Since the 1990s, water and habitat quality has improved in these parts of Europe while in the same period the pressure on aquatic habitats in the Mediterranean has increased greatly.

Rarely have studies assessed Odonata diversity for the entire Nearctic realm by including Canada, the United States, and Mexico. For the first time, we explored Odonata diversity in this region according to a definition of natural community assemblages and generated species distribution models (SDMs). Species occurrence data were assembled by reviewing databases of specimens held by significant Odonata repositories and through an extensive search of literature references. Species were categorized as forest-dependent or non-forest-dependent, as lentic or lotic-dependent, and according to conservation status. Predicted distributions were stacked for all species across their entire ranges, including areas outside of the Nearctic. Species richness and corrected weighted endemism (CWE) were then calculated for each grid cell. We found a pattern of greater species richness in the eastern portion of the Nearctic, which can be explained by the higher aquatic habitat diversity at micro and macroscales east of the Rocky Mountains, promoting niche partitioning and specialization. In the Nearctic region, the southeastern US has the highest number of endemic species of dragonflies and damselflies; this degree of endemism is likely due to glacial refuges providing a foundation for the evolution of a rich and unique biota.

Motivation: Aquatic insects comprise 64% of freshwater animal diversity and are widely used as bioindicators to assess water quality impairment and freshwater ecosystem health, as well as to test ecological hypotheses. Despite their importance, a comprehensive, global database of aquatic insect occurrences for mapping freshwater biodiversity in macroecological studies and applied freshwater research is missing. We aim to fill this gap and present the Global EPTO Database, which includes worldwide geo‐referenced aquatic insect occurrence records for four major taxa groups: Ephemeroptera, Plecoptera, Trichoptera and Odonata (EPTO).Main type of variables contained: A total of 8,368,467 occurrence records globally, of which 8,319,689 (99%) are publicly available. The records are attributed to the corresponding drainage basin and sub‐catchment based on the Hydrography90m dataset and are accompanied by the elevation value, the freshwater ecoregion and the protection status of their location.Spatial location and grain: The database covers the global extent, with 86% of the observation records having coordinates with at least four decimal digits (11.1 m precision at the equator) in the World Geodetic System 1984 (WGS84) coordinate reference system.Time period and grain: Sampling years span from 1951 to 2021. Ninety‐nine percent of the records have information on the year of the observation, 95% on the year and month, while 94% have a complete date. In the case of seven sub‐datasets, exact dates can be retrieved upon communication with the data contributors.Major taxa and level of measurement: Ephemeroptera, Plecoptera, Trichoptera and Odonata, standardized at the genus taxonomic level. We provide species names for 7,727,980 (93%) records without further taxonomic verification.Software format: The entire tab‐separated value (.csv) database can be downloaded and visualized at https://glowabio.org/project/epto_database/. Fifty individual datasets are also available at https://fred.igb‐berlin.de, while six datasets have restricted access. For the latter, we share metadata and the contact details of the authors.