Jael Palhas1, João Cabral3, Francisco Alejandro López Núñez1, Elizabete Marchante1 and Hélia Marchante2
1Centre for Functional Ecology ‐ Science for People & the Planet, Department of Life Sciences, University of Coimbra. Calçada Martim de Freitas, 3000-456 Coimbra, Portugal
2Instituto Politécnico de Coimbra, Escola Superior Agrária, Centre for Functional Ecology – Science for people and the planet, Bencanta, 3045-601 Coimbra, Portugal
3Laboratory of Applied Ecology, CITAB – Centre for the Research and Technology of Agro-Environment and Biological Sciences, University of Trás-os-Montes e Alto Douro, Vila Real, Portugal
Acacia longifolia is one of the most widespread invasive plants in the coastal areas of Portugal, mainly because of its ability to produce a large number of long-lasting seeds that accumulate in soil seed banks. Seeds frequently germinate after disturbance (e.g. fire, control interventions) resulting in rapid reinvasion of the areas. After host‐specificity testing, several years of national and European risk assessments and bureaucratic procedures, the Australian bud‐galling wasp, Trichilogaster acaciaelongifoliae, was introduced as a biocontrol agent (BCA) for Acacia longifolia in late 2015. The wasp is highly host‐specific, exclusively attacking A. longifolia. It is univoltine and most of the annual life cycle is spent as eggs, larvae and pupae within the developing galls. The adults are small (3 mm), short lived (2–3 days) and parthenogenic. After emergence, the females lay their eggs in the flower (and vegetative) buds of A. longifolia which develop into galls instead of pods. This wasp has been used as a biocontrol agent in South Africa for more than 30 years with great success. In the short term, it reduces the annual seed production, which in turn results in fewer seeds for dispersal and in the long-term, it results in a reduction of reinvasion after control operations, fire or other disturbances. We created a dynamic model to simulate the establishment and population growth of this BCA and its impacts on the A. longifolia seed production over time. The model was developed using STELLA 10.0.5 and was divided in three interconnected sub‐models: the climatic scenario, the Acacia model and the Trichilogaster model. The model was featured with an intuitive interface to promote its use by non‐experts in the management of invaded areas, e.g., when deciding how many wasps to release in their areas. Parameters were obtained from a literature review, field records and expert knowledge. Results show that it’s expected an initial exponential growth of the BCA population followed by stabilization with natural fluctuations between years, in response to meteorological variations. Acacia longifolia seedbank in the soil stops growing 5 years after the BCA release and starts decreasing slowly, due to the reduction or even suppression of seed production and stable seedbank loss rate. Advantages of this approach for biocontrol research and for management of invaded areas are discussed.