The project
Biological invasions can profoundly alter natural communities through predation, competition, pathogen transmission and changes to food webs. The laboratory investigates these dynamics in aquatic and terrestrial ecosystems, with particular attention to interactions between native amphibians and reptiles and introduced species.
A major research focus is the American bullfrog, Lithobates catesbeianus (also referred to as Aquarana catesbeiana), which is considered one of the world’s most impactful invasive amphibians. Studies conducted in central Italy, together with analyses of the international literature, have shown that its effects on native communities change during development and also depend on the presence of other invasive species.
Adult bullfrogs can prey on native amphibians, whereas juveniles may compete with them for food and habitat. The presence of the invasive red swamp crayfish, Procambarus clarkii, can modify these interactions: when crayfish are available as prey, bullfrogs tend to consume fewer native amphibians. This finding shows that removing a single invasive species may produce unexpected effects and that management actions need to consider the entire network of interactions.
Research activities also include the study of alien freshwater turtles in urban environments. A survey of 311 ponds, fountains and lakes in Rome recorded six non-native species, with higher occurrence in larger urban lakes, and highlighted the role of pet abandonment in their spread.
Aims
- understand the predation and competition effects of invasive species on native fauna;
- reconstruct trophic interactions using stomach-content analysis, stable isotopes and literature reviews;
- assess how age, behaviour, environmental conditions and the presence of multiple invasive species modify ecological impacts;
- identify the factors promoting the establishment of alien amphibians and reptiles;
- provide scientific guidance for coordinated, ecosystem-based management actions.
Main findings
Studies co-authored by Leonardo Vignoli have shown that:
- the trophic niche of the American bullfrog changes between native and invaded ranges and is influenced by the availability of introduced crayfish;
- the presence of Procambarus clarkii can reduce the occurrence of native amphibians in the bullfrog’s diet;
- the American bullfrog can exert a double impact on native anurans, acting mainly as a competitor when juvenile and as a predator when adult;
- nocturnal brightness and environmental conditions influence activity and habitat use in both the invasive predator and its native prey;
- in urban systems, pond size and type contribute to determining the occurrence of alien freshwater turtles.
Publications
- Bissattini A.M. & Vignoli L. (2017). Let's eat out, there's crayfish for dinner: American bullfrog niche shifts inside and outside native ranges and the effect of introduced crayfish. Biological Invasions.
- Bissattini A.M., Buono V. & Vignoli L. (2018). Field data and worldwide literature review reveal that alien crayfish mitigate the predation impact of the American bullfrog on native amphibians. Aquatic Conservation: Marine and Freshwater Ecosystems.
- Bissattini A.M., Buono V. & Vignoli L. (2019). Disentangling the trophic interactions between American bullfrogs and native anurans: Complications resulting from post-metamorphic ontogenetic niche shifts. Aquatic Conservation: Marine and Freshwater Ecosystems.
- Bissattini A.M., Buono V. & Vignoli L. (2020). Moonlight rather than moon phase influences activity and habitat use in an invasive amphibian predator and its native amphibian prey. Acta Oecologica.
- Di Santo M.P., Vignoli L., Carpaneto G.M. & Battisti C. (2017). Occurrence patterns of alien freshwater turtles in a large urban pond archipelago (Rome, Italy): Suggesting hypotheses on root causes. Lakes & Reservoirs.
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