The value of the species interaction-abiotic stress hypothesis (SIASH) for invasion biology: using native latitude to explain non-native latitudinal range sizes

Abstract

Establishment and spread of introduced species are difficult to predict because they are subject to a myriad of factors. A hypothesis which integrates multiple ecological processes, such as the species interaction-abiotic stress hypothesis (SIASH), may improve our ability to predict introduction success (i.e. establishment and spread). SIASH postulates that, along an environmental gradient, species’ range limits are set by abiotic stress at the environmentally harsh end of that gradient and by species interactions at the environmentally benign end of the gradient. Given that species richness increases nearer the equator and that climate becomes harsher (colder) nearer the poles, latitude represents a useful gradient with which to test simple predictions of SIASH. In order to test whether non-native ranges conform to the predictions of SIASH, we evaluated non-native latitudinal range size data for 195 cross-continental, naturalized introductions of 140 animal and plant species. Median latitude of native range was positively related to range size in the introduced zone, such that species native to high latitudes occupied larger introduced ranges than species native to low latitudes. Furthermore, temperate native species occupied larger latitudinal ranges when introduced to tropical and subtropical zones than did tropical native species introduced to temperate zones. Our results suggest that where a species originates is as important as where it is introduced for predicting introduction success. Abiotic stress from cold more strongly constrains the range extents of introduced species than species interactions, which is particularly pronounced for species originating from tropical regions. Future work should determine how species interactions and abiotic stress jointly explain other components of non-native species’ success across different spatial gradients to better integrate SIASH into invasion biology.