Pilar Alda, Manon Lounnas, Antonio Alejandro Vázquez, Rolando Ayaqui, Manuel Calvopina, Maritza Celi-Erazo, Robert Dillon, Luisa Carolina González Ramírez, Eric S. Loker, Jenny Muzzio-Aroca, Alberto Orlando Nárvaez, Oscar Noya, Andrés Esteban Pereira, Luiggi Martini Robles, Richar Rodríguez-Hidalgo, Nelson Uribe, Patrice David, Philippe Jarne, Jean-Pierre Pointier, Sylvie Hurtrez-BoussèsPlease use the format "First name initials family name" as in "Marie S. Curie, Niels H. D. Bohr, Albert Einstein, John R. R. Tolkien, Donna T. Strickland"
<p>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 phylogenetic relationships of these species with an integrative approach that includes morphology (shell and reproductive anatomy), 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 clusters of species. Four of these clusters (*G. truncatula*, *G. cubensis*/*viator*, *G. humilis* and *G. schirazensis*) are morphologically cryptic and constitute species or species complexes with wide variation in their genetic diversity, geographic distribution and invasiveness. The other two clusters constitute a single species or a species complex (*Galba cousini*/*meridensis*) that demonstrate more geographically restricted distributions and exhibit an alternative morphology more phylogenetically derived than the cryptic one. Further genetic studies are required to clarify the status of both *G. cousini*/*meridensis* and *G. cubensis*/*viator*. We emphasize that no *Galba* species should be identified without molecular markers and that additional sampling is required, especially in North America, Eurasia and Africa to clarify remaining questions in systematics and biogeography. We also discuss several hypotheses that can explain crypsis in *Galba*, such as convergence and morphological stasis, and hypothesize a role for stabilizing selection in amphibious (rather than strictly freshwater) habitats.</p>
systematics, distribution, America, Lymnaeidae, Galba, vector snails, biological invasions
