Invasion on the doorstep: will the Carpathians remain free from the spiny cheek crayfish Faxonius limosus (Rafinesque, 1817)?

The success of biological invasions relies, among other factors, on the abiotic environment. The presence or absence of an invasive alien species in its non-native range may therefore be helpful in understanding the factors facilitating or hampering its invasion. The aim of our study was to determine whether the Carpathians are free from the spiny cheek crayfish Faxonius limosus (Rafinesque, 1817), a successful freshwater invader in Europe and locally in Africa. We hypothesised that local factors, mostly climate (i.e. water temperature). have an impact on this species, limiting its spread. However, atypical local habitats with suitable abiotic conditions-in particular artificial reservoirs-might be hubs for F. limosus. The study was conducted in 2018 in Carpathian waters. We found that despite being present in plain areas adjacent to the Carpathians for decades, F. limosus does not ingress deeper into this mountain range. The exceptions are two dam reservoirs and the lower reaches of some of their tributaries, close to their inflows. The Carpathians are climatically distinct from the surrounding areas, which is also reflected in mean water temperature - ca. 1.5 degrees C lower than in adjacent lowland areas. Thus, we suggest that relatively severe climate may be the main reason behind the limited range of F. limosus in mountains. However, other factors, like current velocity, substrate type, or slope, may contribute to the absence of the species in the studied area. Dam reservoirs providing warmer aquatic habitats and lentic environment may facilitate its invasion related to climate warming.