Modelling of alien insect pestsdistributionat landscape level

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Modelling the dispersal of invasive species using landscape variables

Publication . Nunes, Pedro Mourato Catela; Simões, Manuela Rodrigues Branco; Silva, José Carlos Franco Santos; Jactel, Hervé

Biological invasions are a great threat for ecosystems functioning and human welfare. In many cases, the more realistic strategy in the combat of invasive species is controlling their spatial expansion. Our work focused on studying the role of the landscape structure towards invasive species dispersal. For this we developed three different dispersal models using landscape factors and ecology concepts. Models were applied to two highly relevant invasive species for Europe, the pine wood nematode (PWN) and the african citrus psyllid. To understand the role of landscape heterogeneity towards the spread of the PWN, we studied the dispersal trajectories of the vector, M. galloprovincialis. We used least-cost path analysis to estimate the beetle’s behaviour response to the different land uses from a mark-release-recapture essay conducted in a heterogenous forest. The importance of isolated host trees for invasive species spread was tested in two spatio-temporal models for the dispersal of T. erytreae at large and local scales. At large scale, the role of human activities for the invasion patterns of T. erytreae in Portugal was also addressed. The inclusion of human-mediated spread and isolated host trees improved the F1-Scores of the model validation with the official reports as observations. For the local scale model, in an heterogenous agriculture region, we developed a spatio-temporal model, using an epidemiological approach for the chain of tree infections, to explain the dispersal of the species across the landscape. This model further allowed incorporating different management strategies. Altogether, our findings highlighted the importance that landscape structure, and its elements, can have for invasive species dispersal, making their inclusion invaluable for invasive species modelling. Additionally, we were able to contribute with promising novel methodologies and modelling approaches for invasive biology, including a tool for pinpointing the origin of captured individuals in trapping grids.

2023-12-07Doctoral thesis

Open access

Modelling the invasion dynamics of the African citrus psyllid: The role of human-mediated dispersal and urban and peri-urban citrus trees

Publication . Nunes, Pedro; Robinet, Christelle; Branco, Manuela; Franco, José Carlos

The African citrus psyllid, Trioza erytreae (Del Guercio) (Hemiptera, Triozidae), is native to tropical Africa and invasive species in North America and Europe. The main host plants are citrus, displaying a preference for lemon trees. This psyllid was recently detected in the northwest region of the Iberian Peninsula, both in Spain and Portugal. Here, we used a model combining a reaction-diffusion model to a stochastic long- distance dispersal model to simulate the invasion dynamics of T. erytreae in Portugal. The psyllid spread in Portugal was simulated between 2015 and 2021 for different combinations of model parameters: two fecundity levels; spread with and without stochastic long-distance dispersal; single or two introductions of T. erytreae; and considering or not the urban and peri-urban citrus trees, besides citrus orchards, estimated using Google Street view imagery. The incorporation of long-distance human mediated dispersal significantly improved the F1-score in the model validation using the official reports as the observed data. Concomitantly, the dispersal rate of T. erytreae in Portugal was on average about 66 km/year, whereas removing long-distance dispersal events, the observed mean was 7.8 ± 0.3 km/year. The dispersal was mainly towards the south along the coastline, where human population is concentrated. The inclusion of the estimated citrus trees outside orchards areas significantly increased the F1-score in the model validation, revealing the importance these isolated host plants hold as stepping stones for the species current invasion and possibly for other species alike

2023Journal article

Open access