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Invaders affect native species across multiple trophic levels, influencing the structure and stability of freshwater communities. Based on the ‘trophic position hypothesis’, invaders at the top of the food web are more harmful to native species via direct and indirect effects than trophically analogous native predators are. However, introduced and native predators can coexist, especially when non-native species have no ecological and behavioural similarities with natives, occupy an empty niche, or natives show generalist anti-predator strategies that are effective at the community level. At present, conservation efforts are focused on eradicating invaders; however, their removal may lead to unwanted and unexpected outcomes, especially when invaders are well established and strongly interspersed with natives. This highlights the need to consider invaders in a whole-ecosystem context and to consider the evolutionary history and behavioural ecology of natives and invaders before active management is applied. Here, stomach content and stable isotope analyses were combined to investigate a pond system dominated by invaders in order to understand the effects of the interactions among upper level predators and lower level members of the food web on the whole community structure. Both diet and isotope analyses showed that several invaders contributed to the diet of natives and invaders. A significant isotope overlap was found among upper level predators. However, stomach content analysis suggested that predators reduced the potential competition differentiating the food spectrum by including additional prey in their diet. Both native and non-native upper level predators, by preying on invaders, seem not to exert a strong suppressive effect through predation and competition on native species. This research confirms the importance of studying food webs to identify ecological conditions that forecast the potential for deleterious impacts before management is applied. In cases where invaders cannot be eradicated, management efforts should follow a conciliatory approach promoting the coexistence of native species with invaders.

Amphibians are the vertebrate group experiencing the steepest global population decline and species loss. Habitat alteration and loss caused by the intensification of agriculture is among the main causes; however, in the past, amphibians have been favoured by traditional agriculture and husbandry as more terrestrial and aquatic habitats became available through land-use diversification and the construction of artificial facilities for cattle watering. Troughs for cattle watering may represent the only permanent water points for amphibian reproduction in human-modified landscapes. The present study focused on Lissotriton vulgaris meridionalis, a semi-aquatic salamander, subendemic and widespread in Italy, capable of colonizing artificial aquatic habitats. The main goal was to determine the importance of drinking troughs for the ecology and conservation of the species in a hilly area (Latium region, Central Italy) subjected to traditional livestock farming (i.e. Maremmana cattle). Specifically, generalized linear models (GLMs) were used to analyse the effects of drinking trough characteristics (i.e. size, substrate, aquatic vegetation), landscape features (distance to the forest, forest cover, percentage of cultivated lands and infrastructural development, terrestrial connectivity) and intensity of management practices on the occurrence and abundance of the target species. In the light of the present results, it is suggested that drinking troughs represent suitable surrogates for pristine habitats for L. vulgaris meridionalis. Hence, even man-made aquatic habitats, associated with traditional husbandry, may help to sustain amphibian populations in landscapes where natural wetlands are scarce. The present findings are timely because of the lack of empirical data on the role of drinking troughs in amphibian conservation within rural socio-economic scenarios, which may have been neglected in research and policy in favour of lakes, rivers and streams.