Niche conservatism and the potential for the crayfish Procambarus clarkii to invade South America

Invasive species are one of the most severe threats to biodiversity, and an ability to predict the extent of potential invasions can help conservation strategies. Species distribution models (SDMs) have been widely used to project the potential range of invasive species. These models assume that species retain their niche properties during invasion (niche conservatism), although this assumption is seldom verified. We gathered occurrence records for the crayfish Procambarus clarkii from the U.S.A. and Mexico (native + invasive ranges) and from the Iberian Peninsula (invasive) to test for niche conservatism across continents using niche overlap metrics (Schoener's D). To test for differences in the climate space occupied by the species on the different continents, we performed two principal component analyses (PCAs) on the environmental data extracted from occurrence records: first, separately for each occurrence data set (i.e. each continent) and secondly, using the pooled data. Subsequently, we projected the model to South America, where this species has the potential to become invasive. Schoener's D showed high overlap (0.68) between the two regions (the Americas and Iberia), and there was no difference between the regions in both PCAs. The crayfish has conserved its niche across continents, and therefore, our model projection to South America may accurately demonstrate where invasion is most likely to occur. Large parts of South America are apparently suitable, mainly Argentina, Chile, Paraguay, Uruguay and southern Brazil. This result is of great concern since this invasive species can spread quickly in suitable areas. Stronger laws and regulations should be made to protect native biodiversity and agricultural land. Our approach could be replicated for the study of invasions by other species where extensive data on the potentially invaded areas are available.