INVASION DYNAMICS OF FRESHWATER CRAYFISH IN A MAN-DOMINATED LAND: SPATIO-TEMPORAL, ECOLOGICAL AND HUMAN DIMENSIONS

Biological invasions are among the leading threats to freshwater biodiversity, yet predicting their dynamics and mitigating their impacts remains challenging, especially in human-dominated landscapes where human-aided dispersal is highly possible. This thesis in particular advances understanding of freshwater crayfish invasion dynamics in Lombardy (Northern Italy) by integrating spatio-temporal modelling, impact assessment on native fauna, and socio-managerial perspectives. As the latest comprehensive assessment in the region was carried out in 1994–2006 by Fea et al., Chapter 2 aimed first to update invasive crayfish distribution, compiling occurrences from scientific and grey literature. Moreover, using Maximum Entropy (MaxEnt) modelling, high-suitability areas were identified, while both linear regression and Bayesian diffusion–growth models quantified Procambarus clarkii expansion rates and revealed environmental drivers of dispersal and local population growth. Compiled historical records indicate multiple probable introduction events for both Faxonius limosus, mostly found in major lakes, and for the more widespread P. clarkii. The latter had a steady early-stage (1997–2006) spread of approximately 3.8 km per year near Pavia, strongly facilitated by urbanized low-slope areas and irrigation networks acting as dispersal corridors, whereas forests and natural river margins slightly limited diffusion and offered less suitable habitat for establishment. Second, the field study presented in Chapter 3 warns on the possible negative effects of P. clarkii on native amphibians living at the border of today’s distribution in hilly and mountain areas. The research compares ecological impacts of the native crayfish Austropotamobius pallipes complex and the alien P. clarkii on fire salamander (Salamandra salamandra) larvae. Significantly lower body condition was found in larvae from sites with P. clarkii than those co-occurring with A. pallipes, suggesting stronger predation pressure or indirect effects of the invasive species on resource availability, due to the contrasting functional roles of native versus alien crayfish. Finally, the human dimension in protected areas was explored through visitor surveys in Chapter 4 and management assessments in Chapter 5 to evaluate how the general public behavior and institutional actions influence conservation outcomes. In Monte Barro Regional Park (Chapter 4), surveys revealed low public awareness regarding native and invasive crayfish, with widespread misidentification and limited understanding of actions that could support conservation. Risky behaviors were detected, such as unauthorized fishing, illegal stocking, or entering creeks with potentially contaminated equipment, highlighting the role of human-mediated dispersal in spreading alien species. Importantly, awareness and knowledge were strongly linked to attitudes toward conservation, with better-informed visitors more likely to support eradication of alien species and the protection of native crayfish. At Monza Park (Chapter 5), long-term monitoring showed the local extinction of the Italian agile frog (Rana latastei), likely driven by habitat modification, severe droughts, and predation pressure from invasive P. clarkii, compounded by fragmented management responses. These results underline that effective conservation requires not only ecological interventions, such as habitat protection and species reintroduction, but also proactive engagement with stakeholders and coordinated, consistent management by authorities. Integrating socio-ecological perspectives therefore emerges as essential to anticipate human-driven threats, enhance compliance with conservation measures, and safeguard vulnerable freshwater species in human-dominated landscapes. In conclusion, this thesis demonstrates how combining distribution models, ecological impact assessments, and socio-managerial research can generate useful insights for invasive species management. The findings inform proactive strategies to protect native crayfish and amphibians, particularly through early detection, prioritization of high-risk areas, and integration of public engagement into conservation planning.