Family Hydrobiidae Research Articles

On the genetic diversity and protoconch variability of snails of the genus Caspiohydrobia Starobogatov, 1970 (Caenogastropoda: Hydrobiidae)

The genus Caspiohydrobia belongs to the less-known taxa of the family Hydrobiidae. According to a conchologically-based system, developed in the 1970-1980s by Yaroslav I. Starobogatov and his co-authors, the genus includes around 30 living species. However, the most recent data based on molecular evidence indicate that most (if not all) of these morpho-species should be considered junior synonyms of a widely distributed species, Ecrobia grimmi. However, the vast majority of nominal species described in the genus Caspiohydrobia have never been reassessed by molecular taxonomic methods. In this work, the genetic diversity of Caspiohydrobia spp. was studied based on a large sample taken in Lake Elanach in the Kurgan region (Trans-Urals, Russia). Conchological analysis made it possible to identify 7 nominal species of the genus Caspiohydrobia in the sample, whereas genetically all the studied individuals were the same, sharing a single COI haplotype. A phylogenetic tree of Ecrobia spp. has shown that all studied genetically specimens of Caspiohydrobia (including newly sequenced ones) forms a separate cluster on a cladogram, which can be identified as Ecrobia grimmi s. lato. However, a higher genetic diversity was revealed in a population of Caspiohydrobia spp., from a lake adjacent to the Caspian Sea (West Kazakhstan). Distinct morphotypes in the structure of the protoconch were found in samples of Caspiohydrobia spp. from the Caspian and Aral Seas. Although the characteristics of the protoconch (size, sculpture) do not give grounds to distinguish ‘good’ species within the group, the genetic and morphological diversity described in this work makes it possible to assume the ongoing microevolutionary processes within the discussed group and, possibly, the existence of young (incipient) species in Central Asia. Based on the study of the morphology of the protoconch, it has been suggested that the development of molluscs of the genus Caspiohydrobia (= Ecrobia, partim) can include the free-swimming larval stage; this hypothesis is, however, not supported by other evidence and needs to be carefully verified.

DNA sequence data, multispecies coalescent and morphometrics shed new light on the systematics of Iberian islamiinae springsnails (Caenogastropoda: Hydrobiidae)

ABSTRACT Multilocus phylogenies have shown that soft-part anatomy alone is insufficient for the systematics of valvatiform- and trochiform-shelled springsnails of the subfamily Islamiinae (family Hydrobiidae) due to morphological similarities between taxa that are not closely related. However, a solid knowledge of their systematics and species boundaries is crucial to conserve this highly imperilled group. Here, we inferred molecular phylogenies based on two mitochondrial and two nuclear gene fragments from representatives of three morphological species of the Iberian genus Iberhoratia and performed multispecies coalescent and shell variation analyses (geometric morphometrics) to reevaluate their taxonomic status. The resulting phylogenetic analyses, which included homologous sequences of 15 other valvatiform-shelled hydrobiid species endemic to the Iberian Peninsula, depicted the topotypical specimens of I. aurorae and I. gatoa elisai distantly related to one another and the type species I. morenoi. Considering their high genetic divergence and morphological differences from other hydrobiid taxa, we have placed the former two species in the new genera Beatrix n. gen. and Actenidia n. gen. The multispecies coalescent delimitation method DELINEATE, a novel approach to the taxonomy of the Hydrobiidae, and shell morphometric data suggested two species within the ‘I. gatoa elisai’ clade. Based on morphological and molecular evidence, we recognized this clade as Actenidia, a new genus comprising the species A. elisai n. gen., n. comb. and A. baetica n. gen., n. sp. Our results underscore the importance of using multiple lines of evidence to delimitate species of Islamiinae and interpret their systematics. We also discuss the implications of our findings for conserving I. gatoa.

A holistic perspective on species delimitation outperforms all methods based on single data types in freshwater gastropods (Caenogastropoda: Hydrobiidae: Pseudamnicola)

Abstract Freshwater gastropods are one of the most species-rich and severely threatened animal groups in continental aquatic ecosystems. Unfortunately, understanding their species diversity, which is key to conservation, is often hampered by their small size, simple morphology, and restricted distribution. This is particularly the case for spring snails of the genus Pseudamnicola (family Hydrobiidae), a species-rich taxon across the Mediterranean region. Contrasting species diversities derived from molecular phylogenies and traditional taxonomy call for a holistic approach, in which molecular markers are used to identify putative taxonomic units that can then be validated morphologically. We integrated DNA sequence and morphometric data from 92 populations into a species delimitation framework to assess the taxonomic status of 25 nominal and 14 informally recognized species of Pseudamnicola across its geographical range. Although seven discovery methods delimited a varying number of putative species, taking an integrative approach generally improved species support over single datasets. The statistically favoured integrative scheme corroborated 30 of the 39 initial species as separate entities, whereas nine require taxonomic re-evaluation. Six species are described here formally. Pseudamnicola exemplifies the importance of considering multiple lines of evidence to evaluate species diversity in taxonomically complex groups, with newly developed approaches providing the needed toolbox.

Two new genera and species of the valvatiform hydrobiid snails (Caenogastropoda: Truncatelloidea: Hydrobiidae) from Morocco.

Stygobiont and crenobiont minute gastropods representing the family Hydrobiidae (Caenogastropoda: Truncatelloidea), characterized by the valvatoid low-spired shell, were collected from one spring and four wells in Bouregreg region, NW Morocco. The shells were photographed and measured; shell biometry is illustrated with principal component analysis. Penes were illustrated and described. Mitochondrial cytochrome oxidase subunit 1 (COI) and 16S rRNA, as well as nuclear 18S rRNA sequences were used to infer the phylogeny. The snails represented two genera, both new to science. Their closest relatives were taxa from the Iberian Peninsula, the rough molecular estimate of the time of divergence between these Moroccan and Iberian genera coincided with the Pliocene Flooding, which restored the Strait of Gibraltar to connect the Mediterranean Basin with Atlantic Ocean.

To be alive or not to be alive: Radiocarbon data provide new perspective on species diversity in the Caspian Sea

Abstract The Caspian Sea is undergoing a severe biodiversity crisis. However, estimates of current extinction rates are difficult to obtain due to the lack of reliable pre‐Anthropocene baseline data. For example, because the majority of endemic gastropod species was described from “fresh looking” shells, it remains unclear which species still existed prior to the Anthropocene. This study therefore used the species‐rich microgastropod family Hydrobiidae to assess the extent to which endemic species were collected alive during the Anthropocene. Literature and database searches were performed. In addition, 14C dating was conducted on “fresh looking” shells collected in the Caspian Sea during the last 150 years. The literature review revealed that 75% of the “recent” species are only known from empty shells and 25% were recorded with a soft body. The 14C data showed that all “recent” specimens examined had an age between 1624 cal BC and 1888 cal AD. Two species studied predate the beginning of the Anthropocene. Two other species potentially or likely existed during the Anthropocene. This suggests that the number of endemic species still present at the beginning of the Anthropocene is lower than previously thought. The data also suggest that there was a substantial loss of species between the late 18th century and the 1950s and that only two endemic hydrobiid species have recently been found alive. These findings further contribute to the notion of a severe biodiversity crisis in the Caspian Sea. For accurate estimates of current extinction rates of Caspian Sea gastropods, pre‐Anthropocene biodiversity data need to be further corroborated. Particularly, studies are required to clarify the taxonomic status of the dubious taxa and a possible “collection crisis” in the Caspian Sea due to decreasing sampling efforts in recent decades. In addition, comprehensive IUCN assessments are urgently required.

A systematic review of the Iberian springsnail subgenus Alzoniella (Navarriella) (Caenogastropoda: Hydrobiidae), with the description of a new potentially relict subfamily

Abstract The threatened springsnail subgenus Alzoniella (Navarriella) in the Iberian Peninsula has been suggested to be an old and relict lineage of the family Hydrobiidae. The subgenus is represented by two morphological species, both endemic to the Pyrenees and their southern foothills. We conducted phylogenetic analyses based on mitochondrial and nuclear gene fragments of topotypes and other populations, four molecular species delimitation methods, and morphological examinations to clarify the uncertain systematic position of the subgenus within the family, assess its species diversity, and understand the population genetic structure of the two geographically restricted species. Our phylogenetic results revealed that Alzoniella (Navarriella) is distantly related to all other species of Alzoniella, even belonging to an independent subfamily-level clade, for which we introduce the new genus Navarriella and the new subfamily Navarriellinae subfam. nov. Molecular methods and geometric morphometric analysis of shell shape identified a single species in the new genus. The significant phylogenetic distance from other hydrobiid taxa, narrow distribution, and limited gene flow among its populations (estimated from mitochondrial cytochrome c oxidase subunit I sequences) highlight Navarriella as an isolated lineage within the family that requires urgent conservation attention. Furthermore, our results cast a new light on the northern Iberian Mountains as a dispersal barrier for ancient spring lineages.

Miocene Hydrobiidae (Gastropoda) of the Eastern Paratethys

A review of the family Hydrobiidae from the Tarkhanian and Chokrakian deposits was made. New genus Islamiella was described, in which the species I. miocenica sp. nov. (upper Tarkhanian–lower Chokrakian) and I. maeotica sp. nov. (lower Maeotian) were included. Last species is widely distributed in the facies, concomitant with the bryozoan buildings of the Maeotian beginning. Peringia tarkhanica sp. nov. was described fom the Tarkhanian, whereas Hydrobia kubanica Zhizhchenko, 1936 was redescribed from the Chokrakian. Several species descibed earlier as Hydrobia by Zhizhchenko were synonymized with the species from the other families: H. subprotracta Zhizhchenko, 1936 icluded in synonymy of Finella andrusovi andrusovi (Bajarunas, 1910), and H. stavropoliana Zhizhchenko, 1936 reffered to the genus Odostomia, most probably to species O. nuda Bajarunas, 1910.

Revealing the Stygobiotic and Crenobiotic Molluscan Diversity in the Caucasus: Part IV—Crenobiotic Belgrandiellinae Radoman, 1983 (Mollusca, Hydrobiidae) from Georgia

Since 2020, the south-western Caucasus has been recognized as a hotspot of stygobiotic Mollusca diversity after revealing a large number of new, range-restricted species within the spring snail family Hydrobiidae, subfamily Sadlerianinae sensu Szarowska. Meantime, based on extensive material collected in the south-western Caucasus during the last decades, we studied members of another spring snail subfamily Belgrandiellinae Radoman, 1983. Modern integrative taxonomic work revealed hitherto unknown diversity within this subfamily in the region and further proved the importance of the south-western Caucasus as a hotspot of stygobiotic life. In particular, the subterranean environment and springs of Georgia were known to be inhabited by the genus Tschernomorica Vinarski and Palatov, 2019 with four nominal species. Our research, based on a morpho-anatomical study and genetic investigation of COI/H3 mitochondrial/nuclear markers, revealed additionally seven species and three genera new to science—Colchiella lugella gen. et sp. nov., C. nazodelavo gen. et sp. nov., C. shiksa gen. et sp. nov., C. dadiani gen. et sp. nov., Sataplia cavernicola gen. et sp. nov., Aetis starobogatovi gen. et sp. nov., and Tschernomorica kopidophora sp. nov. —to inhabit the Georgian part of south-western Caucasus. The full taxonomic description of each new taxa, along with the review of habitat characteristics and conservation status, is provided. Molecular genetics suggests that the ancestors of Caucasian Belgrandiellinae have migrated from south-western Europe, probably more than once during the late Messinian and early Pliocene periods. Later, Plio-Pleistocene climate oscillations, particularly the repeated rise and fall of the Black Sea water level, resulted in the isolation and radiation of various lineages within the Caucasus and Crimea.

Biodiversity of Bulgaria: Characteristics, protection and trends

Bulgaria is a medium-sized country located in the eastern part of the Balkan Peninsula. It hosts a rich mycota, flora and fauna, and quite well preserved natural and semi-natural ecosystems. This is mostly due to the country's geographic position between the temperate and subtropical zones, the complex geological history, and the big topographic variety. The high species diversity and endemism determine the high conservation value of Bulgarian biodiversity. The Bulgarian flora consist of more than 4,100 species, including more than 45 species of ferns, 250 species of mosses, and 2,800 higher plant species. The animals established in the country belong to 28 phyla and 75 classes. Vertebrates (858 species) comprise 2.7% of the Bulgarian fauna: 242 fishes and fish-like taxa; 24 amphibians; 40 reptiles; 452 birds; and 101 mammal species. Invertebrates account for more than 31,000 species. Over the past 25 years the number of known animals in the country has increased by over 4,500 species: from 29,000 in 1996 to 33,545 species in 2020. The total number of endemic animals is about 1,400 (4.2%). In some groups, the percentage of endemism is very high (95.5% of snails from the family Hydrobiidae and 71% of Clausiliidae; 53.6% of Diplopoda; 50.0% of terrestrial Isopoda). The richest endemic areas in Bulgaria are mostly in the mountains: Rila Mt.- 268, Pirin Mt. - 220, Western Stara Planina Mt. - 184, Western Rhodopes Mts - 183, and the Central Stara Planina Mt. – 181. Molecular data for Bulgarian animals is still insufficient, although Bulgaria ranks among the top 10 European countries in the proportion of the DNA-barcoded animal taxa; sequence coverage of animal specimens in Barcode of Life data System (BOLD) amounts to approximately 36,000 sequences from more than 7,100 Barcode index numbers (BINs). Bulgaria is part of large-scale initiatives of the European research infrastructure such as the Distributed System of Scientific Collections (DiSSCo) and the MOBILISE COST Action, with mass digitization of museum collections currently underway. Legislation to protect nature in Bulgaria dates back to the end of the 19th century and covers forestry (1890), the protection of certain species (1890's) and hunting (1897). Organized civil movements resulted in the establishment of the Union of Nature Protection (1928), the designation of several nature reserves (1933), and the first National Park (1934). More specific regulation followed with Ordinance for the Protection of Nature (1936). The Red Data Book of Bulgaria was published as early as 1984 (vol. 1, Plants) and 1985 (vol. 2, Animals), with a second updated edition in 2011. Bulgaria is also among the first countries to prepare a National Strategy for Biodiversity Protection (1993, adopted in 1998) following the Convention on Biological Diversity (CBD) process. Since then, several national plans for protection of biodiversity have been adopted including assessments of the threats, objectives, and measures for their achievement. According to recent references, such as the Red Data Book (Beshkov 2011) and the Article 17 reports of 2014 and 2020, the main threats to biodiversity in Bulgaria at the beginning of the 21st century have been human induced degradation: fragmentation and loss of habitats; industrial, agricultural and household waste pollution; direct exploitation of biological resources; genetic ingression and invasive alien species; and global climate change effects. A set of drivers for the loss of biodiversity is related to agriculture and land management, including the whole spectrum from intensification to the abandonment of traditional land, and wetland management practices.

Micro-endemic species of snails and amphipods show population genetic structure across very small geographic ranges.

Understanding variation in population genetic structure, even across small distances and for species with extremely limited ranges, is critical for conservation planning and the development of effective management strategies for imperiled species. Organisms that occupy the same geographic extent can maintain different population structures, ranging from highly diverged to panmictic. Such differences can result from differences in biological characteristics such as dispersal ability or demographic history. We used microsatellite loci to evaluate population genetic structure and variation of four desert spring invertebrates having high to low dispersal ability: the lung snail Physa acuta, two species of gilled snails (Juturnia kosteri and Pyrgulopsis roswellensis; family Hydrobiidae) and the amphipod Gammarus desperatus. The study location represents entire species ranges for the micro-endemic hydrobiids and G. desperatus, while P. acuta is ubiquitous throughout much of North America. We found little evidence of significant population genetic structure for P. acuta and J. kosteri, but much more for P. roswellensis and G. desperatus. Our results demonstrate differences in habitat preference and/or dispersal ability between the species. This information provides insight into how gene flow shapes varying population genetic structure between species across small spatial scales (<100 km2). Most importantly, our results suggest that conservation agencies should not consider these micro-endemic species to be composed of single populations, but rather, that management plans for such species should account for population genetic variation across the species' ranges.

Phylogenetic relationship and habitat both impact the gut microbiome in two microendemic gastropods

ABSTRACT Bacterial communities associated with eukaryotes play important roles in the physiology, development and health of their hosts. Additionally, the composition of microbes associated with eukaryotes can be indicative of evolutionary history, environment and life history. Here, we investigated the microbial ecology of two sympatric caenogastropod taxa belonging to the family Hydrobiidae, Juturnia kosteri and Pyrgulopsis roswellensis. The diversity and composition of the microbiota were described based on high-throughput Illumina sequencing targeting the V4 region of the 16S rRNA gene. The observed bacterial diversity was distributed over 16 phyla, with the greatest number of 16S rRNA gene sequences derived from Proteobacteria, Bacteroidetes, Tenericutes and Planctomycetes. These results document the presence of highly diverse gut bacterial communities in the two hydrobiid species. While alpha-diversity measures were consistent across species and sites, beta-diversity measures revealed significant differences in species, collection site and the interaction of both variables. These results indicate a mixed interaction, with both species and site impacting the microbiome. However, principal coordinate analysis indicated no separation between snail species at site BLU7 (Bitter Lake Unit 7). The high impact of site on microbial communities implies that although these species have different phylogenetic histories, they show similarities in their microbiomes when occupying overlapping habitats. Further investigation into biotic and abiotic factors is necessary to elucidate differences in microbial communities between sympatric snail species.

Shell features and anatomy of the springsnail genus Radomaniola (Caenogastropoda: Hydrobiidae) show a different pace and mode of evolution over five million years

Abstract Shell features are key factors for systematics and evolutionary biology studies of freshwater gastropods. Based mostly on shell morphology, 19 species of the springsnail genus Radomaniola (family Hydrobiidae) have been described. Although the scarce differentiation of various shell dimensions suggests morphological stasis, the evolutionary dynamics of shell and other anatomical structures have not yet been explored fully. By inferring a phylogeny and a time-calibrated species tree from mitochondrial (COI and 16S) and nuclear (28S) sequences of 15 recognized species, we initially examine the species diversity of the Radomaniola dataset and then, through phylogenetic comparative methods, assess the evolutionary correlation, pace and mode of 40 continuous shell and anatomical characters. By synthesizing the results of four species delimitation methods and through morphological examinations, we recognize 21 groups, for which taxonomy is discussed here. Seven new species are described. We reveal a high degree of correlated evolution between characters of the shell, which are constrained by a single morphological optimum, consistent with the morphological stasis model. Anatomical traits diverged rapidly in an unconstrained manner or toward multiple optima. These findings indicate that in order to understand the morphological evolution of springsnails, it is essential to examine different organs in detail.

Holotypes for three Caspian gastropods of the family Hydrobiidae tracked down: description and taxonomic interpretations.

Type series of three nominal taxa of the hydrobiid gastropods inhabiting the Caspian Sea were traced recently in the uncatalogued part of the malacological collection of the Zoological Institute of Russian Academy of Sciences, Saint-Petersburg. Images of the holotypes and some paratypes of Pyrgula isseli Logvinenko Starobogatov, 1969, P. sowinskyi Logvinenko Starobogatov, 1969 and P. derzhavini Logvinenko Starobogatov, 1969 are presented. The first two species belong to the genus Clathrocaspia (subfamily Caspiinae) and P. sowinskyi is considered a junior synonym of C. pallasii (Clessin W. Dybowski in W. Dybowski, 1887). The attribution of the third species, P. derzhavini, to Laevicaspia (Pyrgulinae) is confirmed based on the newly discovered type material. Based on the additional information we update ecological data and distribution ranges of the species, provide comments on their nomenclature, systematic position and taxonomic rank.

Arganiella Giusti &amp; Pezzoli, 1980 (Caenogastropoda: Truncatelloidea: Hydrobiidae): a widespread genus or several narrow-range endemic genera?

Most valvatiform genera of the gastropod family Hydrobiidae are narrow-range taxa. One exception is the genus Arganiella, which is comprised of three congeners: the type species A. pescei from the Apennine Peninsula, A. wolfi from the Iberian Peninsula and A. tabanensis from the Balkans. The genus assignment of the latter two species was based on morphological similarities with A. pescei in the shell, operculum, radula and genitalia. Given that the morphology of hydrobiids is sometimes susceptible to convergence, this study re-evaluates the taxonomic status of species of Arganiella by analysing mitochondrial (mtCOI) and nuclear (18S rRNA) sequences of topotypes or near topotypes to infer their phylogenetic position. Our phylogenetic analyses depicted Arganiella as a non-monophyletic group within Hydrobiidae, and sequence divergence among the three species ranged from 14.5 to 16.7% for mtCOI and 2.0 to 3.8% for 18S. We also re-examined the extent of morphological variation among species of Arganiella and found a few differences among them and other valvatiform genera. Consequently, we propose two new genera for A. wolfi and A. tabanensis. Our results conflict with the classification of valvatiform hydrobiid species solely based on traditional phenotypical methods and suggest further taxonomic evaluation within a molecular framework.

Hidden species diversity of Corrosella Boeters, 1970 (Caenogastropoda: Truncatelloidea) in the Moroccan Atlas reveals the ancient biogeographic link between North Africa and Iberia

Despite the high species richness of freshwater gastropods in the western Mediterranean, the evolutionary patterns of the North African taxa are poorly understood. In a recent survey of spring habitats in the Atlas Mountains of Morocco (western Maghreb), we discovered ten snail populations anatomically resembling the genus Corrosella (family Hydrobiidae), which was supposedly endemic to the Iberian Peninsula and southern France. Through morphological and molecular investigations, we assessed the taxonomic status of these populations and their evolutionary origins. Molecular phylogenies based on three gene fragments (COI, 16S rRNA and 28S rRNA) from snails of the newly collected populations and 12 additional congeners distributed across the Iberian Peninsula and southern France clustered together the Moroccan populations within Corrosella in a well-supported clade comprising six putative species: two previously identified as Hydrobia marocana and Pseudamnicola pallaryi and four unknown lineages here described as species new to science. According to a molecular clock analysis calibrated with an external rate, the Moroccan clade originated ca. 7.6 million years ago (Mya) (11–4.5 Mya) and its divergence from the southern Iberia lineages likely occurred 8.4 Mya (12.5–5.5 Mya). This suggests that the biogeography of Corrosella in the western Maghreb has been shaped by old vicariance events likely associated with the Late Miocene-Pliocene geological setting of the region and their interplay with the isolation conditions of springs. Our findings considerably expand knowledge of the diversity and geographic range of Corrosella and provide new insight into faunal relationships between North Africa and Europe.

Two new genera and three new subterranean species of Hydrobiidae (Caenogastropoda: Truncatelloidea) from Tunisia

The aquatic biodiversity of springs and groundwater systems of North Africa remains largely unexplored. In an earlier field survey of Tunisian springs, a new gastropod genus, Bullaregia, was discovered as a phylogenetically independent lineage of uncertain position within the family Hydrobiidae. Here, we provide taxonomic and phylogenetic assignments for three newly collected populations of hydrobiids from springs in northern Tunisia based on morphological, anatomical and genetic (mtCOI and 18S) data. Among these and specimens of Bullaregia, major differences were observed in male and female genitalia as well as in mtCOI sequences (divergence 8.0–9.1%). Based on these findings, we describe two new genera and three new species: Belgrandiellopsis chorfensis gen. et sp. nov., Belgrandiellopsis secunda gen. et sp. nov. and Biserta putealis gen. et sp. nov. In all our phylogenetic analyses, these three new species were well resolved as a monophyletic group together with Bullaregia tunisiensis. Unexpectedly, this clade emerged as sister to the European valvatiform genera Corbellaria and Kerkia and not to the recently discovered clade of groundwater, conchologically similar, species living in Bulgaria (Balkan Peninsula). These Tunisian species are each locally endemic and form part of a newly discovered clade which in future systematic studies could eventually be identified as a distinct hydrobiid subfamily.

NEW SUBTERRANEAN FRESHWATER GASTROPOD SPECIES FROM MONTENEGRO (MOLLUSCA, GASTROPODA, MOITESSIERIIDAE, AND HYDROBIIDAE)

During the field trips to Bosnia &amp; Hercegovina and Montenegro in the years 2015 - 2018 we investigated the subterranean freshwater gastropod fauna in several karst springs. Five subterranean gastropod species new to science had been recorded within the collected material. Three of the new species are assigned to the family Moitessieriidae: Paladilhiopsis cattaroensis n. sp., Paladilhiopsis matejkoi n. sp., Bosnidilhia vitojaensis n. sp. and two to the family Hydrobiidae: Plagigeyeria feheri n. sp. and Stygobium hercegnoviensis n. sp., the latter in the new genus Stygobium.

Multilocus phylogeny, species delimitation and biogeography of Iberian valvatiform springsnails (Caenogastropoda: Hydrobiidae), with the description of a new genus

AbstractValvatiform gastropods of the family Hydrobiidae are frequently found in European spring-fed systems. Their simplified and sometimes convergent morphological structures and restricted geographical ranges make the description and identification of valvatiform species challenging. In the Iberian Peninsula, to date, 20 valvatiform species have been described morphologically. To test morphological species delimitations and to evaluate the role of physical geography on their evolutionary history, we analysed two mitochondrial (COI and 16S rRNA) and two nuclear (28S rRNA and 18S rRNA) gene fragments of 16 valvatiform species from the Iberian Peninsula. Molecular species delimitation methods consistently inferred 11 of the nominal species. Our phylogenetic analyses recovered the species Islamia azarum as an independent lineage, distantly related to other genera, which we place in the new genus Deganta. Furthermore, Iberian valvatiform hydrobiids do not form a monophyletic subunit, but they are included in two distinct clades of Hydrobiidae. Divergence times indicate that speciation in these clades is likely to have coincided with the formation of major Iberian mountain ranges and river basins. Similarities of geographical subdivision and divergent times between this assemblage and the non-valvatiform genus Corrosella provide strong evidence for the role of the Iberian geographical barriers in shaping the biogeography of these springsnails.

Two new oligohaline Hydrobia (s.l.) (Caenogastropoda) from the transitional Upper Oligocene Galatone Fm (Apulia, Southern Italy)

Species-poor assemblages rich in specimens of non-marine to brackish molluscs occur in Oligocene stratigraphical successions, widely exposed in the Salento region (southernmost Apulia, Italy). Two new extinct oligohaline gastropods of the family Hydrobiidae (Caenogastropoda), Hydrobia (s.l.) galatoniana n. sp. and Hydrobia (s.l.) ionica n. sp., are described from the type-section of a richly fossiliferous transitional succession, the Late Oligocene (Chattian) Galatone Fm, cropping out in the Lecce district. This lithostratigraphical unit records foraminiferal, molluscan and ostracod assemblages indicative of alternating oligohaline to shallow water lagoonal and littoral marine conditions. At some silty levels of the investigated succession, the two new species occur in dense populations forming shell-beds in oligotypical assemblages, accompanied by smooth-shelled ostracods. An oligohaline environment is proposed for these assemblages. This paper represents a contribution to the knowledge of Oligocene hydrobiids from Italy, where their record is extremely scarce and poorly known.

Global species richness of hydrobiid snails determined by climate and evolutionary history

Abstract Efforts to describe spatial patterns of freshwater diversity and to evaluate their underlying factors have traditionally been focused on some animal groups (e.g. amphibians, fish or dragonflies). Despite being a dominant component in continental aquatic ecosystems and crucial for determining priority areas for conservation, broad‐scale data on gastropod total species, endemic and threatened species richness are limited. Based on these biodiversity indices, we identify global hotspots, extinction risk along the elevational gradient and the drivers of species richness patterns in the largest group of freshwater gastropods, the family Hydrobiidae. Given the strong dependency to a nonmarine aquatic environment, the observed richness patterns of extant hydrobiid species could be significantly influenced by large‐scale geography and dispersal processes as well as climatic conditions affecting continental ecosystems. Therefore, we tested several predictions for species richness derived from ecological and evolutionary hypotheses postulated for other freshwater groups. Based on a comprehensive literature and biodiversity database review, we compiled the number of total, endemic and threatened species per freshwater ecoregion. We classified ecoregions as hotspots if each biodiversity index was in the top 25% of its range and assessed the effect of 13 environmental and evolutionary factors on species richness using generalised linear models. We identified 906 species and 157 genera of Hydrobiidae showing mainly a Nearctic–Palearctic distribution and 19 biodiversity hotspots, most located across the Mediterranean Basin. In our data set, 83% of the species were endemic to a single ecoregion. Of the 43% non‐data deficient species, we found almost three times more threatened than non‐threatened species, and extinction risk peaked at 1,500 m a.s.l. Species richness was unequally distributed over biogeographic realms, increased with higher connectivity among ecoregions, and was negatively related with annual temperature range. Latitude and precipitation seasonality explained part of the richness variation by a nonlinear relationship. The identified hotspots correspond with those of other freshwater taxa. The hump‐shaped relationship of extinction risk with elevation is likely the consequence of decreasing natural and anthropogenic perturbations at higher elevations. Global hotspots of Hydrobiidae richness represent areas of climatic stability with medium precipitation and temperature seasonality that are well connected with other hydrological basins. Our results illustrate that both evolutionary and environmental factors determine these global patterns and that future changes of the latter factors may affect hydrobiid richness.