LB 27-237 - Exploring Niche Dynamics can Improve Model Parameterization and Management for Non-native Species

Ecological niche models (ENMs) are widely used for risk assessment of non-native species. Some non-native species occupy different niches in their native and introduced ranges, affecting the transferability of ENMs, thus making risk assessment challenging. We show that exploring niche dynamics of non-native species can inform model calibration and improve transferability. Examining realized niche dynamics can also provide information about the stage of invasion and potential for future expansion, which is crucial for effective management. We investigated niche dynamics of Rainbow trout (Oncorhynchus mykiss) and Brown trout (Salmo trutta fario), introduced in the Himalayan ecoregion for commercial and recreational purposes. These non-native trout compete for space and resources with two native flagship species i.e., Schizothorax plagiostomus and Schizothorax richardsonii. Little is known about the invasive potential of non-native trout in the Himalayas which impedes making clear policies about their propagation via hatchery programs. We used the COUE framework (Centroid shift, Overlap, Unfilling, and Expansion) to study niche dynamics, and overlap of non-native trout with Schizothorax species. While the fundamental niche may be stable, we found no significant conservatism in the realized niches for rainbow and brown trout. We observed more “expansion” to new habitats for Brown trout (74%) than for Rainbow trout (39%). Similarly, Brown trout had more potentially suitable conditions yet to fill, “unfilling” (23%) compared to Rainbow trout (7%). Our analyses suggest more invasive potential for Brown trout in the Himalayas. However, Rainbow trout has more realized niche overlap with Schizothorax species and in case of invasion, may negatively affect Schizothorax species more than Brown trout. These niche dynamics indices suggest developing a global model (developed with information from both native and introduced ranges), parameterized flexibly to allow making predictions in the Himalayas. Our results provide baseline information on invasive potential and realized niche overlap between non-native trout and Schizothorax species in the Himalayas. Our framework demonstrate that realized niche dynamics can inform model parameterization and management for non-native species in the Himalayas and elsewhere.