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Biological invasions: patterns and processes. An integrative approach with the Bullfrog Rana catesbeiana in Canada and Europe

Final Activity Report Summary - INTEGRINVA (Biological invasions: patterns and processes. An integrative approach with the Bullfrog Rana catesbeiana in Canada and Europe)

The programme aimed to understand the patterns and progress of biological invasion using the American bullfrog as model organism in Canada and Europe. The origin of introduced populations in Europe was identified by genetic analysis. The 397 individuals that were analysed shared five different haplotypes, corresponding to 12 introduced European populations, while 41 haplotypes were present in the 42 native populations in North America. The phylogeographical analysis suggested that at least five independent bullfrog introductions occurred in Europe. A similar analysis was ongoing, by the time of the project completion, to identify the origin of introduced population in western North America and Canada.

The Bullfrog invasiveness was studied via an analysis of climatic variables that explained distribution in the native range and were then projected at the worldwide scale. Several ongoing invasions agreed with this global model of invasion risk. At the regional scale of northern Italy, models taking into account landscape change, mainly due to human activities, showed great performance in describing bullfrog invasion.

The skeletochronological method was also used to assess age structure in native and introduced populations. The analysis was performed for six populations and was in progress by the time of this report for the remaining collected samples. We had to increase the number of populations sampled in the native range, hence new collaborations were been built in, for example, Michigan, Louisiana and Georgia.

The collection of available complementary data on the biology and human contributions to the current invasions was still in progress. We additionally focused on eradication and control effort and methods. A questionnaire was sent to people involved in invasive bullfrog management worldwide. The answers, summarising control effort, methods, budget etc. would allow building optimisation models to classify control methods according to cost and results. The final aim of this programme was to provide the best estimate of a management strategy to control bullfrog invasion in Europe. We were on the way to produce it and tested the applicability of most of the control technique, as well as methods to validate it, in two populations in France and one population in Canada.