Systematics and geographical distribution of Galba species, a group of cryptic and worldwide freshwater snails

Cryptic species can present a significant challenge to the application of systematic and biogeographic principles, especially if they are invasive or transmit parasites or pathogens. Detecting cryptic species requires a pluralistic approach in which molecular markers facilitate the detection of coherent taxonomic units that can then be analyzed using various traits (e.g., internal morphology) and crosses. In asexual or self-fertilizing species, the latter criteria are of limited use. We studied a group of cryptic freshwater snails (genus Galba) from the family Lymnaeidae that have invaded almost all continents, reproducing mainly by self-fertilization and transmitting liver flukes to humans and livestock. We aim to clarify the systematics, distribution, and phylogeny of these species with an integrative approach that includes morphology, molecular markers, wide-scale sampling across America, and data retrieved from GenBank (to include Old World samples). Our phylogenetic analysis suggests that the genus Galba originated ca. 22 Myr ago and today comprises six species or species complexes. Four of them show an elongated-shell cryptic phenotype and exhibit wide variation in their genetic diversity, geographic distribution, and invasiveness. The remaining two species have more geographically restricted distributions and exhibit a globose-shell cryptic phenotype, most likely phylogenetically derived from the elongated one. We emphasize that no Galba species should be identified without molecular markers. We also discuss several hypotheses that can explain the origin of cryptic species in Galba, such as convergence and morphological stasis.

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Fil: Lounnas, Manon. Centre National de la Recherche Scientifique; Francia. Université Montpellier; Francia

Fil: Vázquez, Antonio A.. Instituto de Medicina Tropical Pedro Kourí; Cuba. Centre National de la Recherche Scientifique; Francia. Université Montpellier; Francia

Fil: Ayaqui, Rolando. Universidad Nacional de San Agustin de Arequipa; Perú

Fil: Calvopiña, Manuel. Universidad de Las Américas; Ecuador

Fil: Celi Erazo, Maritza. Universidad Central de Ecuador; Ecuador

Fil: Dillon, Robert T.. Freshwater Gastropods of North America Project; Estados Unidos

Fil: González Ramírez, Luisa Carolina. Universidad Nacional de Chimborazo. Facultad de Ciencias de la Salud. Grupo de Investigación Análisis de Muestras Biológicas y Forenses Laboratorio Clínico; Ecuador

Fil: Loker, Eric S.. University of New Mexico; Estados Unidos

Fil: Muzzio Aroca, Jenny. Ministerio de Salud Pública. Instituto Nacional de Investigación en Salud Pública Dr. Leopoldo Izquieta Perez; Ecuador

Fil: Nárvaez, Alberto Orlando. Ministerio de Salud Pública. Instituto Nacional de Investigación en Salud Pública Dr. Leopoldo Izquieta Perez; Ecuador. Universidad Agraria del Ecuador; Ecuador

Fil: Noya, Oscar. Universidad Central de Venezuela; Venezuela. Ministerio del Poder Popular para la Salud. Instituto Nacional de Higiene Rafael Rangel; Venezuela

Fil: Pereira, Andrés Esteban. Universidad Industrial Santander; Colombia

Fil: Robles, Luiggi Martini. Laboratorio de Parasitologia Luiggi Martini y Colaboradores; Ecuador

Fil: Rodríguez Hidalgo, Richar. Universidad Central del Ecuador; Ecuador

Fil: Uribe, Nelson. Universidad Industrial Santander; Colombia

Fil: David, Patrice. Centre National de la Recherche Scientifique; Francia. Université Paul Valéry; Francia

Fil: Jarne, Philippe. Centre National de la Recherche Scientifique; Francia. Université Paul Valéry; Francia

Fil: Pointier, Jean Pierre. Centre National de la Recherche Scientifique; Francia. Université de Perpignan; Francia. Université de recherche Paris Sciences et Lettres; Francia

Fil: Hurtrez Boussès, Sylvie. Centre National de la Recherche Scientifique; Francia. University of Montpellier; Francia