Global diversity of dragonflies (Odonata) in freshwater

Larvae of almost all of the 5,680 species of the insect order Odonata (dragonflies and damselflies) are dependent on freshwater habitats. Both larvae and adults are predators. The order is relatively well studied, and the actual number of species may be close to 7,000. Many species have small distributional ranges, and are habitat specialists, including inhabitants of alpine mountain bogs, seepage areas in tropical rain forests, and waterfalls. They are often successfully used as indicators for environmental health and conservation management. The highest diversity is found in flowing waters in rain forests of the tropics, the Oriental and Neotropical regions being the most speciose. This paper discusses diversity, summarises the biogeography of dragonflies in the different biogeographical regions and gives the total number of species and genera per family per biogeographical region. Examples are given of areas of particular diversity, in terms of areas of endemism, presence of ancient lineages or remarkable recent radiations but no well-based review of areas with high endemism of dragonflies is available so far. The conservation status of dragonflies is briefly discussed. Species confined to small remnants of forest in the tropics are most under threat of extinction by human activities. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Global diversity of cladocerans (Cladocera; Crustacea) in freshwater

Cladocera is a primarily-freshwater monophyletic group, an important component of the microcrustacean zooplankton. They inhabit most types of continental fresh and saline water habitats, occurring more abundantly in both temporary and permanent stagnant waters. Cladocera is an ancient group of Palaeozoic origin. About 620 species are currently known, but we estimate that the real number of species is 2–4 times higher. A number of currently-recognised widespread species can be expected to harbour extensive cryptic diversity. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of tardigrades (Tardigrada) in freshwater

Tardigrada is a phylum closely allied with the arthropods. They are usually less than 0.5 mm in length, have four pairs of lobe-like legs and are either carnivorous or feed on plant material. Most of the 900+ described tardigrade species are limnoterrestrial and live in the thin film of water on the surface of moss, lichens, algae, and other plants and depend on water to remain active and complete their life cycle. In this review of 910 tardigrade species, only 62 species representing13 genera are truly aquatic and not found in limnoterrestrial habitats although many other genera contain limnoterrestrial species occasionally found in freshwater. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Global diversity of non-biting midges (Chironomidae; Insecta-Diptera) in freshwater

Chironomidae are common inhabitants of most aquatic habitats, and often dominate aquatic insect communities in both abundance and species richness. Species occur in all continents, including Antarctica, and most major oceanic islands that have been investigated. The family is divided into 11 subfamilies and 22 nominal tribes. Although individual species occur in a wide range of habitats from terrestrial to fully aquatic, a total of 339 genera and 4,147 species are unambiguously aquatic in their immature stages. Greatest species and generic richnesses occur in the Palaearctic Region and Nearctic Region, respectively, but this pattern may largely reflect historical patterns of past taxonomic research efforts. Guest editors: E.V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of springtails (Collembola; Hexapoda) in freshwater

Water-dependency appeared independently in several clades of the class Collembola, which is basically of terrestrial origin according to recent phylogenetic analyses. Though moderately diversified (less than 8,000 species), Collembola are among the most numerous terrestrial arthropods in wetland communities, with a small number of species living on the surface of water. Many species are dependent on water-saturated atmosphere of caves, and on snow or ice in high mountains. A total of 525 water-dependent species have been recognized, of which 103 are linked to free freshwaters and 109 to anchialine or marine waters. Many interstitial species are also dependent to an unknown extent on water saturation in the deep layers of the soil. The numbers provided here are underestimates, as Collembola are extremely poorly known outside the Holarctis, and the ecology of described species usually not documented. However, a general biogeographical pattern is emerging from available data. The most remarkable feature is that about 15% of the fauna is water-dependent in the holarctic region, compared to 4% in the tropics and southern hemisphere. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of polychaetes (Polychaeta; Annelida) in freshwater

A literature review of Polychaeta (Annelida) including Aphanoneura (the oligochaete-like Aeolosomatidae and Potamodrilidae), living in freshwater yielded 168 species, 70 genera and 24 families representing all of the major polychaete clades, but less than 2% of all species. The best-represented families were, in order, Nereididae, Aeolosomatidae, Sabellidae, Spionidae and Histriobdellidae. Fourteen families were represented by a single species and genus. Regions supporting the highest diversity of freshwater polychaetes were in order, Palaearctic, Neotropical, Oriental, Nearctic, Australasian, and Afrotropical. More than half of all species and genera inhabitat lakes and rivers, followed by lagoons/estuaries, which have a high proportion of euryhaline species, and inland seas. Less common, atypical polychaete habitats include subterranean waters, the hyporheic zone of rivers and plant container habitats (phytotelmata). At least three distinct ecological/historical processes appear to account for the colonisation of continental waters: invasion of a clade prior to the break-up of Gondwana, as in Aphanoneura, Namanereis, Stratiodrilus, and Caobangia; relatively recent stranding of individual species (relicts); and the temporary visitation of euryhaline species. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Latitudinal changes in the diversity of freshwater gastropods (Mollusca: Gastropoda) in waterbodies of western Siberia

The patterns of spatial variation in gastropod diversity in the waterbodies of western Siberia have been revealed. The highest species and generic diversity of freshwater gastropods is found in the waterbodies of the forest-steppe zone; from there, these parameters significantly decrease northwards, reaching their minimum beyond the polar circle. The proportion of gastropods of non-European origin increases in the same direction. The possible reasons for these changes in the spatial diversity of aquatic gastropods and the likely connections between the latitudinal variation of their diversity and the geological history and features of the relief of western Siberia are discussed. It is assumed that the forest-steppe zone of western Siberia is a local center of aquatic gastropod diversity.     

Global diversity of mayflies (Ephemeroptera, Insecta) in freshwater

The extant global Ephemeroptera fauna is represented by over 3,000 described species in 42 families and more than 400 genera. The highest generic diversity occurs in the Neotropics, with a correspondingly high species diversity, while the Palaearctic has the lowest generic diversity, but a high species diversity. Such distribution patterns may relate to how long evolutionary processes have been carrying on in isolation in a bioregion. Over an extended period, there may be extinction of species, but evolution of more genera. Dramatic extinction events such as the K-T mass extinction have affected current mayfly diversity and distribution. Climatic history plays an important role in the rate of speciation in an area, with regions which have been climatically stable over long periods having fewer species per genus, when compared to regions subjected to climatic stresses, such as glaciation. A total of 13 families are endemic to specific bioregions, with eight among them being monospecific. Most of these have restricted distributions which may be the result of them being the relict of a previously more diverse, but presently almost completely extinct family, or may be the consequence of vicariance events, resulting from evolution due to long-term isolation. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of amphipods (Amphipoda; Crustacea) in freshwater

Amphipods are brooding peracaridan crustaceans whose young undergo direct development, with no independent larval dispersal stage. Most species are epibenthic, benthic, or subterranean. There are some 1,870 amphipod species and subspecies recognized from fresh or inland waters worldwide at the end of 2005. This accounts for 20% of the total known amphipod diversity. The actual diversity may still be several-fold. Amphipods are most abundant in cool and temperate environments; they are particularly diversified in subterranean environments and in running waters (fragmented habitats), and in temperate ancient lakes, but are notably rare in the tropics. Of the described freshwater taxa 70% are Palearctic, 13% Nearctic, 7% Neotropical, 6% Australasian and 3% Afrotropical. Approximately 45% of the taxa are subterranean; subterranean diversity is highest in the karst landscapes of Central and Southern Europe (e.g., Niphargidae), North America (Crangonyctidae), and Australia (Paramelitidae). The majority of Palearctic epigean amphipods are in the superfamily Gammaroidea, whereas talitroid amphipods (Hyalella) account for all Neotropic and much of the Nearctic epigean fauna. Major concentrations of endemic species diversity occur in Southern Europe, Lake Baikal, the Ponto-Caspian basin, Southern Australia (including Tasmania), and the south-eastern USA. Endemic family diversity is similarly centered in the Western Palearctic and Lake Baikal. Freshwater amphipods are greatly polyphyletic, continental invasions have taken place repeatedly in different time frames and regions of the world. In the recent decades, human mediated invasions of Ponto-Caspian amphipods have had great impacts on European fluvial ecosystems. Guest editors: E. V. Balian, C. Lévêque, H. Segers and K. Martens Freshwater Animal Diversity Assessment     

Global diversity of nemerteans (Nemertea) in freshwater

Most ribborn worms (phylum Nemertea) are marine and only 22 of the currently named around 1,200 species are known from freshwater habitats (mainly lakes/ponds). They are all free-living benthic forms found in all continents except Antarctica. The vast majority of species have been recorded from the Palearctic region, but this may reflect sampling efforts rather than biogeography. Guest editors: E.V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of freshwater mussels (Mollusca, Bivalvia) in freshwater

The term freshwater bivalve is very inclusive and not very informative. There are representatives of at least 19 families that have at least one representative living in freshwater. This suggests at least 14 different invasions of freshwater. At least nine families have small to large radiations in the freshwater environment: Corbiculidae, Sphaeriidae, Dreissenidae, and the unioniforme families: Hyriidae, Margaritiferidae, Unionidae, Etheriidae, Iridinidae, and Mycetopodidae. The unioniforme families contain at least 180 genera and about 800 species. This order is characterized by the unique parasitic larval stage on the gills, fins or the body of a particular host fish. This order of freshwater bivalves is suffering a very high rate of extinction, with about 37 species considered presumed extinct in North America alone. The level of endangerment and extinction facing these animals is primarily the result of habitat destruction or modification. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of mammals (Mammalia) in freshwater

Species that are dependant on, or adapted to, freshwater environments are found in almost all mammalian orders, and two orders, the Cetacea and the Sirenia, are strictly aquatic and include some freshwater-dependant species. Overall, the aquatic and freshwater-dependant species represent around 70 of the more than 1,200 living or recent genera of mammals, and occur in all continents except Antarctica. They include some of the most endangered species of mammals, and several have gone extinct or become critically endangered in recent decades. One of the main threats is habitat loss or degradation. This chapter provides an overview of the freshwater species within each order of mammals, their evolutionary history, their relations to humans and their conservation status. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Global diversity of caddisflies (Trichoptera: Insecta) in freshwater

The not yet uploaded Trichoptera World Checklist (TWC) [], as at July 2006, recorded 12,627 species, 610 genera and 46 families of extant and in addition 488 species, 78 genera and 7 families of fossil Trichoptera. An analysis of the 2001 TWC list of present-day Trichoptera diversity at species, generic/subgeneric and family level along the selected Afrotropical, Neotropical, Australian, Oriental, Nearctic and Palaearctic (as a unit or assessed as Eastern and Western) regions reveals uneven distribution patterns. The Oriental and Neotropical are the two most species diverse with 47–77% of the species in widespread genera being recorded in these two regions. Five Trichoptera families comprise 55% of the world’s species and 19 families contain fewer than 30 species per family. Ten out of 620 genera contain 29% of the world’s known species. Considerable underestimates of Trichoptera diversity for certain regions are recognised. Historical processes in Trichoptera evolution dating back to the middle and late Triassic reveal that the major phylogenetic differentiation in Trichoptera had occurred during the Jurrasic and early Cretaceous. The breakup of Gondwana in the Cretaceous led to further isolation and diversification of Trichoptera. High species endemism is noted to be in tropical or mountainous regions correlated with humid or high rainfall conditions. Repetitive patterns of shared taxa between biogeographical regions suggest possible centres of origin, vicariant events or distribution routes. Related taxa associations between different regions suggest that an alternative biogeographical map reflecting Trichoptera distribution patterns different from the Wallace (The Geographical Distribution of Animals: With a Study of the Relations of Living and Extinct Faunas as Elucidating the Past Changes of the Earth’s Surface, Vol. 1, 503 pp., Vol. 2, 607 pp., Macmillan, London, 1876) proposed biogeography patterns should be considered. Anthropogenic development threatens biodiversity and the value of Trichoptera as important functional components of aquatic ecosystems, indicator species of deteriorating conditions and custodians of environmental protection are realised.     

Global diversity of water mites (Acari,Hydrachnidia; Arachnida) in freshwater

The Hydrachnidia (water mites) represent the most important group of the Arachnida in fresh water. Over 6,000 species have been described worldwide, representing 57 families, 81 subfamilies and more than 400 genera. The article analyzes extant water mite diversity and biogeography. Data on distribution and species richness of water mites are substantial but still far from complete. Many parts of the world are poorly investigated, Oriental and Afrotropical regions in particular. Moreover, information among different freshwater habitats is unbalanced with springs and interstitial waters disproportionately unrepresented. Therefore, more than 10,000 species could be reasonably expected to occur in inland waters worldwide. Based on available information, the Palaearctic region represents one of the better investigated areas with the highest number of species recorded (1,642 species). More than 1,000 species have been recorded in each of the Neotropical (1,305 species) and Nearctic regions (1,025 species). Known species richness is lower in Afrotropical (787 species) and Australasian (694 species) regions, and lowest in the Oriental region (554 species). The total number of genera is not correlated with species richness and is distinctly higher in the Neotropical (164 genera); genus richness is similar in the Palaearctic, Nearctic and Australasian regions (128–131 genera) and is lower in the Afrotropical and Oriental regions with 110 and 94 genera, respectively. A mean number of about three genera per family occur in the Palaeartic, Nearctic and Oriental while an average of more than four genera characterizes the families of Australasian and Afrotropical regions and more than five genera those of the Neotropical. Australasian fauna is also characterized by the highest percentage of endemic genera (62%), followed by Neotropical (50.6%) and Afrotropical (47.2%) regions. Lower values are recorded for the Palaearctic (26.9%), Oriental (24.4%) and Nearctic (21.4%). The Palaearctic and Nearctic have the highest faunistic similarity, some minor affinities are also evident for the generic diversification of Holarctic and Oriental families. The faunas of Southern Hemisphere bioregions are more distinct and characterized by the presence of ancient Gondwanan clades with a regional diversification particularly evident in the Neotropics and Australasia. This scenario of water mite diversity and distribution reflect the basic vicariance pattern, isolation, phylogenetic diversification, recent climatic vicissitudes and episodes of dispersal between adjacent land masses together with extant ecological factors can be evoked to explain distribution patterns at a global scale. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of butterflies (Lepidotera) in freshwater

In Lepidoptera, the subfamily Acentropinae and Pyraustinae of Crambidae (Pyraloidea) and the family Arctiidae (Noctuoidea) contain species with true aquatic larvae, which live submerged during larval development. In Pyraustinae and Arctiidae only a few species exhibit an aquatic life-history. From the latter, aquatic larvae are known from the Neotropical genus Paracles. The number of aquatic Paracles species is unknown. The Acentropinae are predominantly aquatic. They are distributed worldwide, and reach the highest diversity in tropical regions of South East Asia/Malesia and in the Neotropical Region. At present, the Acentropinae include a total of 50 genera and 737 described species. All genera, assigned to the subfamily, are listed in a table, and the numbers of included species are indicated. The taxonomy and phylogeney of the genera are inadequately known. The species have a minor economic importance, however, they are very sensitive to degradation of water quality and habitat destruction. Guest editors: E.V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of bryozoans (Bryozoa or Ectoprocta) in freshwater

The present study considers 88 bryozoan species occurring in freshwater: 69 phylactolaemate and 19 gymnolaemate species. Roughly 49% of these species are confined to one zoogeographical region. The cosmopolitan status of species like Fredericella sultana, Plumatella repens or P. emarginata has to be reconsidered. Among the Phylactolaemata, which are phylogenetically older than the Gymnolaemata, the gelatinous species (Lophopodidae, Pectinatellidae, Cristatellidae) are more primitive than the branching tubular species (Plumatellidae, Fredericellidae). Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment     

Global diversity of fishlice (Crustacea: Branchiura: Argulidae) in freshwater

The Branchiura of freshwater habitats, consisting of the valid genera Argulus, Chonopeltis, Dipteropeltis, and Dolops, presently contains 113 valid species and 12 undescribed species. The entire group is composed of ectoparasitic species that usually live on fishes. The highest diversity of genera and species occurs in the Afrotropical and Neotropical regions. The diversity of the freshwater species surpasses that of species in marine and brackish waters, but this could be due to inadequate study of the fauna of the latter habitats. One species, Argulus japonicus, has been introduced from east/southeast Asia to all other continents, except Antarctica. Studies of higher level relationships place the Branchiura with either Pentastomida or Ostracoda. Hypotheses about phylogenetic relationships of either the genera or species in this group have not been proposed. Guest editors: E. V. Balian, C. Lévêque, H. Segers & K. Martens Freshwater Animal Diversity Assessment The present paper was intended as a very brief overview of the known diversity of the Branchiura in freshwaters only, and regrettably is deficient in mention of much information and many relevant citations pertaining to the group.     

Phylogeny and systematics of mitriform gastropods (Mollusca: Gastropoda: Neogastropoda)

With about 800 Recent species, ‘miters’ are a widely distributed group of tropical and subtropical gastropods that are most diverse in the Indo‐West Pacific. They include the two families Mitridae and Costellariidae, similar in shell morphology and traditionally treated as close relatives. Some genera of deep‐water Ptychatractidae and Volutomitridae are close to miters in shell morphology, and the term ‘mitriform gastropods’ has been introduced to refer to Mitridae, Costellariidae, and this assortment of convergent forms. The present study aimed at the reconstruction of phylogenetic relationships of mitriform gastropods based on representative taxon sampling. Four genetic markers [cytochrome c oxidase subunit I (COI), 16S and 12S rRNA mitochondrial genes, and H3 (Histone 3) nuclear gene] were sequenced for over 90 species in 20 genera, and the molecular data set was supplemented by studies of radula morphology. Our analysis recovered Mitridae as a monophyletic group, whereas the genus Mitra was found to be polyphyletic. Of 42 mitrid species included in the analysis, 37 formed a well‐supported ‘core Mitridae’ consisting of four major clades, three of them consistent with the subfamilies Cylindromitrinae, Imbricariinae, and Mitrinae, and Strigatella paupercula standing out by itself. Basal to the ‘core Mitridae’ are four minor lineages, with the genus Charitodoron recognized as sister group to all other Mitridae. The deep‐water family Pyramimitridae shows a sister relationship to the Mitridae, with high support for a Pyramimitridae + Mitridae clade. Our results recover the monophyly of the Costellariidae, which form a well‐supported clade that also includes Ptychatractidae, Columbariinae, and Volutomitridae, but not Mitridae. Most derived and diverse amongst Costellariidae are species of Vexillum, characterized by a bow‐shaped, multicuspidate rachidian tooth. Several previously unrecognized deep‐water costellariid lineages are revealed. Their members retain some plesiomorphies – in particular a tricuspidate rachidian tooth – that makes them morphologically intermediate between ptychatractids and Vexillum. The taxa of Ptychatractidae included in the analysis are not monophyletic, but form three well‐supported, unrelated groupings, corresponding respectively to Ceratoxancus + Latiromitra, Exilia, and Exiliodea. None of them shows an affinity to Pseudolividae. © 2015 The Linnean Society of London