Using avatar species to model the potential distribution of emerging invaders
crayfish, Ecological niche model, Invasive species, Mahalanobis Distance, niche conservatism, niche shift, risk assessment, Species distribution model
Aim: Anticipating the potential distributions of emerging invasive species is complicated by the tendency for species distribution models to perform better when both native and invasive range data are available for model development. If invasive range data are lacking, species models are liable to under-estimate distributions for emerging invaders, particularly for species that are not at equilibrium with their native range environment due to historical factors, dispersal limitation and/or ecological interactions.We demonstrate the potential to use well-quantified niche shifts from established ‘avatar’ (i.e. the remote or virtual manifestation of an entity) invaders to develop plausible distributions for data-poor emerging invaders con- tingent on niche shifts of similar magnitude or character. Location: Global. Methods: Using the globally invasive crayfishes Pacifastacus leniusculus and Pro- cambarus clarkii as our avatar invaders, we quantify how niche position, size and structure differs between native and total ranges using Mahalanobis distance (a measure of multivariate similarity) and the climate predictors of annual minimum and maximum air temperature. We then generalize patterns of niche shift from these species to the emerging crayfish invader Cherax quadricarinatus. Results: Some patterns of niche shifts were similar for Pacifastacus leniusculus and Procambarus clarkii, but niche shifts were of considerably greater magnitude for P. clarkii. When a native range model for C. quadricarinatus was modified with generalized niche shifts similar to Pacifastacus leniusculus and Procambarus clarkii, the potential global distribution for this species increased considerably, including many areas not identified by the native range model. Main conclusions We illustrate the potential to use avatar invaders to provide cautionary, niche shift-assuming species distribution models for emerging invad- ers.Many theoretical and applied implications of the avatar species concept require additional investigation, including the development of frameworks to select appro- priate avatar species and evaluate the performance of avatar-derived models for emerging invaders. Despite these research needs, we believe this concept will have considerable utility for predicting vulnerability to invasion by data-poor species; this is a critical management need because shifting pathways of introduction and climate change will produce many novel, emerging invasive species in the future.