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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.
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.
Phylogenetic analyses of the highly diverse (non-marine aquatic) gastropod family Hydrobiidae Stimpson, 1865 have revealed seven main lineages, most of which represent subfamilies. The subfamily Pseudamnicolinae Radoman, 1977, and specifically the genus Pseudamnicola Paulucci, 1878 (mainly inhabiting western and central Mediterranean regions), contributes substantially to this hydrobiid richness. Most of its congeners have been described in terms of their shell and penis features, which are of limited diagnostic value. Hence, the taxonomic status of some Pseudamnicola species needs to be revised, particularly of those inhabiting marginal regions, such as the Ponto-Caspian domain, largely occupied by the subfamily Pyrgulinae Brusina, 1882. Here we present a molecular phylogeny including species of both subfamilies along with extended morphological descriptions to confirm assignments of the Iranian species Pseudamnicola zagrosensis Glöer & Pešić, 2009; Sarkia kermanshahensis Glöer & Pešić, 2009 (originally within Pseudamnicola) and P. saboori Glöer & Pešić, 2009. Our COI-based tree rejects these assignments suggesting a new potential lineage, sister to the pyrgulinid species, and comprising three genera: Shadinia Akramowski, 1976, Intermaria gen. nov. and Persipyrgula gen. nov. These genera differ molecularly by 3.6%–8.5%, and are diagnosable by penis, female genitalia and radula features. Our findings evidence the high morphological variability of pyrgulinid species and provide insight into the origins and evolution of the freshwater Ponto-Caspian fauna.
The freshwater snail genus Mercuria is widely distributed in lowland waters across Western Europe, Northern Africa and the Mediterranean islands. Approximately two-thirds of the currently recognised species are described based on their shell morphology, which may vary within species due to biotic and abiotic factors. Recent molecular phylogenies that included numerous previously documented populations recovered 14 species clades, nine of which correspond to nominal species and five, to undescribed taxa. Here, we formally describe the five undescribed taxa as new species and provide morphological descriptions of the shell and other anatomical structures for three of the other inferred clades and for the species M. maceana to elucidate their taxonomic status and assess the utility of morphological characters for species delimitation in Mercuria. Taken together, the morphological and molecular evidence suggest new identifications and synonymies, having implications on the known geographic range of the studied species, including the type species M. similis. Anatomical measurements and geometric morphometric analysis of shell shape revealed no clear differentiation among the species analysed, predicting the importance of molecular data in elucidating the species diversity of the genus.
The species richness of the aquatic (non-marine) gastropod family Hydrobiidae Stimpson, 1865 reaches its peak in the European region partly because other areas, such as North Africa, remain to be extensively surveyed. Most of the hydrobiid species described in North Africa have been ascribed to the subfamilies Pseudamnicolinae, Hydrobiinae and the genus Mercuria. Little is known about the presence of other hydrobiid subfamilies. This study examines several specimens of gastropods collected from two springs in Tunisia. Based on a comprehensive literature review and rigorous anatomical and molecular comparisons with known species from North Africa, Europe and Asia Minor of similar morphology, we here describe a new genus, Bullaregia gen. nov., and new species Bullaregia tunisiensis gen. et sp. nov. Although the shell shape of this Tunisian species resembles that of European hydrobiid genera such as Belgrandiella, it differs in other anatomical structures (i.e., penis with a glandular strap-like lobe, and two seminal receptacles, SR1 pedunculate, SR2 sessile and less developed). Using maximum likelihood and Bayesian approaches, phylogenetic relationships inferred from mtCOI sequences point to an independent evolutionary lineage for this new taxon outside Belgrandiella and other known hydrobiid subfamilies.