Shell Variation of Springsnail Populations in the Cuatro Cienegas Basin, Mexico: Preliminary Analysis of Limnocrene Fauna

Geographic variation in shell morphometry is analyzed for three locally endemic springsnail (Gastropoda: Hydrobiidae) species occurring sympatrically in nine limnocrenes of the Cuatro Cienegas Basin, Coahuila, Mexico. Despite some correlation of size-related variables across species, groupings of populations based on multivariate analyses were not very similar among species, nor were they strongly concordant with current drainage configurations in the basin. Groups of populations of Mexipyrgus churinceanus Taylor having different patterns of shell sculpture and color banding (and once considered separate species) were not separated similarly on basis of shell size and shape. Inter-population differentiation of these snails was approximately equivalent to that of Nymphophilus minckleyi Taylor, whereas Mexithauma quadripaludium Taylor was less variable.