Ecological impact of freshwater invaders: A case study of gastropod assemblages in karstic spring ecosystems

Abstract Throughout the world, the exceptional biodiversity and endemism of spring ecosystems are threatened by the expansion of invasive species. However, mechanisms affecting the distribution and impact of invasive species on spring macroinvertebrate communities remain poorly understood. We investigated the impact of the invasive New Zealand mud snail Potamopyrgus antipodarum on the native gastropod assemblages of 43 karstic springs in Bosnia and Herzegovina. Firstly, we showed that P. antipodarum invaded only human‐modified low‐altitude springs with lower dissolved oxygen concentrations (7.61 mg/L), where it co‐occurred only with four other gastropod species (out of the 17 recorded in our dataset), two of which are endemic Dinaric karst spring specialists. Then, by comparing the n ‐dimensional ecological space of the springs invaded and uninvaded by the mud snail, we showed that low‐altitude springs have a higher risk of invasion. Finally, we characterized the shift in the niche optimum exhibited by native endemic gastropods in invaded springs using Huisman–Olff–Fresco models. Overall, we showed that human alterations of low‐altitude springs might facilitate the invasion of P. antipodarum , which possibly out‐competes endemic crenic species by displacing them to suboptimal niches. The use of Huisman–Olff–Fresco models and n ‐dimensional hypervolumes together provided a useful framework for quantifying the response of endemic and endangered species to the spread of invaders in globally endangered spring habitats.