THE NEW ZEALAND MUDSNAIL, POTAMOPYRGUS ANTIPODARUM, HAS INVADED NUMEROUS COUNTRIES AROUND THE WORLD, INCLUDING CHILE. AIM. WE AIMED TO DETERMINE VARIATION IN SHELL MORPHOLOGY AND FECUNDITY IN 12 POPULATIONS SCATTERED IN SIX HYDROLOGICAL BASINS IN THIS COUNTRY. METHODS. POPULATIONS WERE COMPARED USING SHELL MORPHOMETRY, PRINCIPAL-COMPONENT ANALYSIS (PCA), AND BROOD SIZE. INDEPENDENT LINEAR MIXED MODELS (LMM) WERE APPLIED TO STUDY SPATIALLY CORRELATED DATA. RESULTS. THE MORPHOMETRIC ANALYSIS SHOWED SIGNIFICANT DIFFERENCES IN SHELL VARIABLES, WHEREAS THE PCA SHOWED A HIGH DEGREE OF OVERLAP OF SPECIMENS AS WELL AS SEPARATION OF POPULATIONS IN THE MORPHOMETRIC SPACE. BROOD SIZE DIFFERED SIGNIFICANTLY AMONG POPULATIONS, RANGING FROM 0 TO 63 OFFSPRING. ALTITUDE AND SHELL LENGTH HAD AN EFFECT ON BROOD SIZE, WHEREAS SHELL LENGTH SHOWED VARIATION AMONG BASINS. LATITUDE DID NOT HAVE A DIRECT EFFECT ON ANY OF THE TWO VARIABLES. CONCLUSIONS. POTAMOPYRGUS ANTIPODARUM EXHIBITS GREAT MORPHOLOGICAL AND LIFE HISTORY TRAIT VARIATION, WHICH COULD BE FAVOURING ITS RAPID EXPANSION IN CHILE. THE LACK OF GENETIC VARIATION OF THIS SPECIES, PREVIOUSLY REPORTED IN THE COUNTRY, SUGGESTS THAT DIFFERENCES FOUND IN OUR STUDY ARE LIKELY TO BE DUE TO ENVIRONMENTAL VARIATION. IMPLICATIONS. FURTHER STUDIES SHOULD BE ADDRESSED TO ASSESS THE ORIGIN OF THE VARIANCE.