Abstract
Niche shifts and environmental non-equilibrium in invading alien species undermine niche-based predictions of alien species’ potential distributions and, consequently, their usefulness for invasion risk assessments. Here, we compared the realized climatic niches of four alien amphibian species (Hylarana erythraea, Rhinella marina, Hoplobatrachus rugulosus, and Kaloula pulchra) in their native and Philippine-invaded ranges to investigate niche changes that have unfolded during their invasion and, with this, assessed the extent of niche conservatism and environmental equilibrium. We investigated how niche changes affected reciprocal transferability of ecological niche models (ENMs) calibrated using data from the species’ native and Philippine-invaded ranges, and both ranges combined. We found varying levels of niche change across the species’ realized climatic niches in the Philippines: climatic niche shift for H. rugulosus; niche conservatism for R. marina and K. pulchra; environmental non-equilibrium in the Philippine-invaded range for all species; and environmental non-equilibrium in the native range or adaptive changes post-introduction for all species except H. erythraea. Niche changes undermined the reciprocal transferability of ENMs calibrated using native and Philippine-invaded range data. Our paper highlights the difficulty of predicting potential distributions given niche shifts and environmental non-equilibrium; we suggest calibrating ENMs with data from species’ combined native and invaded ranges, and to regularly reassess niche changes and recalibrate ENMs as species’ invasions progress.
Highlights
Niche shifts and environmental non-equilibrium in invading alien species undermine niche-based predictions of alien species’ potential distributions and, their usefulness for invasion risk assessments
Rhinella marina and H. rugulosus showed niche expansion into non-analogous environmental space
Our findings revealed evidence of conservatism in the Philippine niches of R. marina and K. pulchra, and a shift in the Philippine niche of H. rugulosus
Summary
Niche shifts and environmental non-equilibrium in invading alien species undermine niche-based predictions of alien species’ potential distributions and, their usefulness for invasion risk assessments. Potential distributions of alien species can be predicted by projecting ecological niche models across spatio-temporal space, enabling researchers and environmental managers to assess geographical invasion risks and identify areas where an alien species can potentially enter, establish, spread, and cause significant impacts (i.e., susceptible and sensitive sites sensu McGeoch et al.20)[13]. These predictions can, help in implementing effective biosecurity strategies[15]. These limitations of ENMs have raised doubts on their usefulness for invasion risk assessments[23,40,41,42]
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