Abstract
The western Palearctic freshwater snail genus Mercuria (Caenogastropoda: Hydrobiidae) comprises 26 species primarily distributed in lowland localities of Western Europe and North Africa. Although this genus in North Africa has received considerable attention in terms of species discoveries through morphological descriptions, its distribution and phylogenetic patterns remain unknown. Based on morphological and mitochondrial DNA (mtCOI) evidence, this study examines the three Mercuria species (M.bakeri, M.tingitana, and M.targouasensis) from Morocco identified so far. Besides expanding on information regarding the anatomy of these species, two new species (M.midarensissp. n. and M.tensiftensissp. n.) are described for this region and phylogenetic relationships inferred between these species and the European M.emiliana and M.similis. All Moroccan and European species were recovered as independent entities according to these phylogenetic inferences (uncorrected p-distances 2.8–8.5%) and DNA barcode data. Moroccan Mercuria species clustered with M.emiliana from Spain, although basal relationships within this clade were not well supported. Given that factors such as the season when specimens are collected, habitat type, and parasites could be responsible for the remarkable intraspecific variation observed in shell and penis morphology, it is proposed that the most efficient approach to delimit and identify Mercuria species is to combine morphological descriptions with genetic data.
Highlights
Our objectives were: (1) to delimit the formerly known and potential new Moroccan species of Mercuria under the phylogenetic species concept previously applied to hydrobiids (e.g., Delicado et al 2012, Hershler et al 2013); (2) to examine intra- and interspecific genetic variation and resolve phylogenetic relationships based on mitochondrial DNA (mtCOI) sequences; and (3), to provide habitat and ecological data for future conservation plans
Based on ca. 400 bp obtained from their paratypes, M. bakeri and M. tingitana were recognized as potentially different sister species
The additional sampling effort made for this study extends the distribution range of M. targouasensis from southern to central Morocco
Summary
The gastropod genus Mercuria Boeters, 1971 (Truncatelloidea, Hydrobiidae) is widely distributed in continental aquatic systems of western Mediterranean territories and islands (Giusti 1979, Boeters 1988, Glöer et al 2010, Patzner and Glöer 2013, Boeters and Falkner 2017) and more rarely in those of the Atlantic coasts of North Africa (Glöer et al 2015) and Western Europe (Boeters 1988, Kadolsky 2011, Glöer et al 2015, Boeters and Falkner 2017) and Madeira (Glöer et al 2015). Mercuria species occupy a wide variety of aquatic habitats, typically living in high abundance in springs and their outflows, coastal streams, and tide areas of rivers Less frequently they appear in brackish meadows and ponds. Despite their high representation in lowland aquatic biotopes, phylogenetic relationships among Mercuria congeners have been scarcely explored Species assignments of these snails have been based on conchological and anatomical studies. Based on molecular data obtained for the species Mercuria similis (Draparnaud, 1805), Wilke et al (2013) recovered this genus as an independent lineage within the Hydrobiidae, which was further designated as the subfamily Mercuriinae (Boeters and Falkner 2017)
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