Forecasting the distribution of Marmorkrebs, a parthenogenetic crayfish with high invasive potential, in Madagascar, Europe, and North America

The parthenogenetic marbled crayfish, Marmorkrebs, has high potential to become an invasive species because single individuals can establish a population. Marmorkrebs have already been introduced in several countries, have successfully established populations in at least two of them, and are rapidly expanding in one case (Madagascar). To assess the potential ecological threat arising from further Marmorkrebs introductions, we developed four species distribution models using the distribution of Procambarus fallax (the sexual form of Marmorkrebs) and exotic populations of Marmorkrebs in Madagascar and Europe. The models were applied to three regions where Marmorkrebs pose a conservation concern: Madagascar, where Marmorkrebs populations are growing; Europe, where individuals have been found repeatedly, and where some Marmorkrebs populations arc becoming established, and; North America, where Marmorkrebs are sold as pets, which presents a risk of introduction into North American ecosystems. All models predicted that eastern Madagascar provides suitable habitat for Marmorkrebs. Most models suggested that relatively small areas of Europe are suitable habitat, although a model that includes locations of Marmorkrebs introductions in Europe predicts much of Europe could be suitable, which is supported by recent discoveries of populations in Germany. All models predicted that the south eastern United States, Cuba, and much of Mexico arc also potential habitats. The climatic variable with the greatest predictive power was precipitation in the warmest quarter, which may reflect a susceptibility to drought that has been documented for P. fallax.