Taxonomic assessment of 24 hydrobiid species (Caenogastropoda, Truncatelloidea) of conservation concern in springs of Iberia and Maghreb

Corrosella (family Hydrobiidae) represents one of the most diverse and threatened groups of spring snails in the Iberian Peninsula and Maghreb. Accurate delineation of species boundaries and understanding their geographic distributions are critical for effective conservation. However, inconsistent criteria used to define the 25 currently recognised species have led to considerable taxonomic uncertainty. This study presents a systematic revision of 24 species of Corrosella through an integrative approach combining multilocus phylogenies, morphometric analyses of shells and anatomical traits, and ecological characterisation, with comprehensive datasets for 22 species. Molecular and morphological evidence support the synonymisation of C. navasiana, C. collingi, C. tajoensis, C. valladolensis valladolensis, and C. segoviana under the earliest available name C. navasiana. Furthermore, we formally describe C. ballestae Delicado & Ramos sp. nov., a previously unrecognised species, and provide a redescription of the taxonomically complex C. hinzi. Despite a pronounced DNA sequence divergence among most species, morphological and ecological traits show significant overlap, underscoring the indispensable role of molecular data in resolving species diversity. These taxonomic updates refine the classification of Corrosella, elucidate species distributions, and establish a robust framework to support future research and conservation strategies.