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Freshwater jellyfish (= limnic medusa‐budding hydrozoans, FWJ) are a small group of cnidarians found on all continents except Antarctica in temperate to tropical latitudes. Members of this group belong primarily to three genera: Astrohydra, Craspedacusta, and Limnocnida. While Astrohydra and Limnocnida are typically restricted to the islands of Japan, Africa, and the Indian subcontinent, one species or potential species complex, Craspedacusta sowerbii, became globally invasive. Despite research going back about one‐and‐a‐half centuries, little is known about their phylogeny and ecology compared to marine jellyfish. Recent species distribution modelling, however, showed that by 2050, C. sowerbii will potentially extend their distribution ranges due to global warming to high‐latitude ecosystems and be present (medusa stage) for an extended time in the seasonal limnic production cycle. An increase in their relative ecological importance with temporal and spatial spreading is hypothesised. Only recently, it has been shown that the trophic roles of polyps and medusae and their prey overlap with other ecosystem members. In addition, medusa behaviour may cause trophic cascades and alter vertical nutrient distributions. However, polyps and other benthic life cycle stages are understudied. In globally, changing freshwater ecosystems that may become more accommodating for FWJ, an improved understanding of their population biology and ecosystem ecology is urgently needed. In this integrative review, we, therefore, explore reasons for the hampered historical research progress, contrast developments with those of marine cnidarians, compile and publish alongside an extensive and unprecedented literature database, and formulate avenues for future directions in FWJ research. [ABSTRACT FROM AUTHOR]

Simple Summary: Cordulegastridae, recognized for their striking black-and-yellow colouring, are robust and large dragonflies typically found in clean running springs and streams, which are unfortunately facing significant threats worldwide. Currently, 52 species are listed in this family. Cordulegastridae are remarkably uniform in the structure of the male appendages and the female valvular scale, while the pattern of yellow markings on the abdomen and thorax may vary even within a taxon. This often results in confusion regarding the identification, distribution, and intraspecific division of many species in this family. To address these challenges, we undertook a molecular phylogenetic analysis of this family. Our analyses supported most of the traditional genera. The well-known bidentata group of the current Cordulegaster, including C. coronata and its sister species C. brevistigma, was transferred by us to the genus Thecagaster. The genus Neallogaster remained unresolved. However, Cordulegaster pekinensis, currently known as Neallogaster pekinensis, was placed by us in the genus Thecagaster as well. The genus Zoraena stat. rev. was recovered to include most of the American members of Cordulegastridae, except for C. virginiae and, tentatively, C. diadema, which were retained in the genus Cordulegaster along with the members of the Cordulegaster boltonii group. The monophyly of the genus Anotogaster was confirmed, and three dubious species of this genus were synonymized. Our revision provides a clearer understanding of the evolutionary relationships and taxonomic framework of the family Cordulegastridae. In this study, we present the first attempt at a molecular phylogenetic analysis of the entire family of Cordulegastridae involving 60% of its known species. Our analysis is in favor of reclassification of the members of the family into four genera: (i) the monophyletic genus Anotogaster Selys, 1854, with the number of known species reduced by three synonymizations; (ii) the genus Cordulegaster Leach in Brewster, 1815 including all members of the boltonii group and, as a preliminary solution, the American species C. virginiae Novelo-Gutiérrez, 2018 and, very tentatively, C. diadema Selys, 1868. The bidentata group forms a genus of its own, for which we restored the name Thecagaster Selys 1854, stat. rev. Cordulegaster pekinensis McLachlan in Selys, 1886, currently considered as Neallogaster pekinensis, was placed by us in Thecagaster as well. The genus Neallogaster Cowley, 1934 needs further investigation involving all remaining species listed in it. The genus Zoraena Kirby, 1890, stat. rev., was recovered to accommodate the remaining American species of Cordulegaster. We synonymized three species of Anotogaster: Anotogaster gregoryi Fraser, 1923 = Anotogaster xanthoptera Lohmann, 1993, syn. nov.; Anotogasterkuchenbeiseri (Förster, 1899) = Anotogaster antehumeralis Lohmann, 1993, syn. nov.; Anotogaster kuchenbeiseri (Förster, 1899) = Anotogaster cornutifrons Lohmann, 1993, syn. nov., based on examination of the existing type specimens. The type of specimens of A. klossi Fraser, 1919 = A. flaveola Lohmann 1993 syn. confirm., were also examined, and their synonymy was confirmed. The isolated populations of A. sieboldii (Selys, 1854) from the archipelagos of Okinawa and Amami Oshima in Japan, respectively, should be regarded as separate species, which will be described elsewhere. Furthermore, we suggest the synonymization of Cordulegaster parvistigma Selys 1873 syn. nov. with Thecagaster brevistigma (Selys 1854) comb. restaur. [ABSTRACT FROM AUTHOR]

Aeshnidae Rambur, 1842 are impressive large insects distributed worldwide. Currently, over 500 species are recognized. Nevertheless, the phylogeny of this family is not completely understood. We applied molecular phylogenetic analysis using two popular phylogenetic markers, the mitochondrial COI gene fragment (barcoding sequence) and the nucleic ITS region, containing the ITS1, 5.8S rRNA, and ITS2 sequences. We used available and credible published sequences and 96 newly sequenced specimens. Our analysis involved all West Palaearctic species, all but one genera of the Holarctic Aeshnidae, and most genera worldwide, and is by far the largest molecular study of this family. The topology of all trees created with different algorithms and genes is in favour of the current taxonomic concept, with some remarkable outcomes. Aeshna Fabricius, 1775, was found to be diverged into several branches, especially with respect to the COI gene. Although it appeared not monophyletic in phylogenetic reconstructions based on the ITS region, the analysis of COI and joint analysis suggest its monophyly in the current taxonomical sense, with one notable exception. Aeshna isoceles (Müller, 1767) has fallen out of Aeshna in all analyses, so a new monophyletic genus, Isoaeschna gen. nov. is introduced for it. The genus Brachytron Evans, 1845 tightly clustered with Aeschnophlebia Selys, 1883, Epiaeschna Hagen in Selys, 1883, and Nasiaeschna Selys in Förster, 1900. Thus, we suggest subsuming these four genera under the priority name Brachytron. Tetracanthagyna Selys, 1883 clusters as expected with Brachytron in the ITS tree, but is an independent ancient clade of its own in all COI trees. The genus Polycanthagyna Fraser, 1933 syn. nov. is synonymised to Indaeschna Fraser, 1926. On the species level, we suggest that the American Aeshna septentrionalis Burmeister, 1839 be treated as a subspecies of A. caerulea (Ström, 1783), Aeshna caerulea septentrionalis. We synonymize Gynacantha hyalina Selys, 1882 with Gynacantha subinterrupta Rambur, 1842. Our analysis provides new insights on the tight relationships of the circumboreal species Aeshna juncea and A. subarctica and the intraspecies phylogeny of Aeshna juncea. [ABSTRACT FROM AUTHOR]