Mada
In front of a jury made up of :
Ms Alessandra Marieli Vacari, Professor, University of Franca, Franca - SP, Rapporteur
Pedro Henrique Brum Togni, Professor, University of Brasilia, Brasília - DF, Rapporteur
Pierre Franck, Research Fellow, INRAE, Horticultural Plants and Cropping Systems, Avignon, Examiner
Armin Bischoff, Professor at UMR IMBE, Avignon - Thesis supervisor
Mr Odair Aparecido Fernandes, Professor at UNESP, Brazil - Thesis supervisor
Summary of work:
Forest fragments integrated into agricultural landscapes play a fundamental role in maintaining insect biodiversity and providing associated ecosystem services. This thesis aims to analyse how vegetation characteristics and landscape composition influence insect communities and their functional roles, in tropical and temperate agricultural contexts, with particular attention to pest regulation, pollination and the stability of ecological interactions. The work was carried out in two contrasting regions: sugarcane plots adjacent to fragments of Atlantic forest in south-east Brazil, and vineyards in south-east France. By integrating studies in different environmental and agricultural contexts, this thesis provides an in-depth understanding of the contribution of semi-natural habitats to biodiversity conservation and the functioning of agroecosystems. The first part looks at the relationship between the diversity of trees found in forest fragments and the diversity and abundance of insect functional groups within forests and in adjacent agricultural plots. The data, collected over a two-year period, show that the specific richness of trees is positively correlated with insect diversity and with an increased frequency of key functional groups such as predators and phytophages. Positive correlations between insect diversity in forests and in agricultural plots suggest spillover from forests, highlighting the role of forest fragments as sources of biodiversity and potential providers of ecosystem services. The second part focuses on the order Hymenoptera, a group with remarkable taxonomic and functional diversity, including parasitoids, predators and pollinators. Analysis of the seasonal variation in their abundance and community composition reveals temporal dynamics that vary according to habitat. Forest fragments show more stable communities over time, while sugarcane plots show more marked fluctuations, probably linked to agricultural practices and greater microclimatic variations. The responses of the functional groups vary according to season and habitat, underlining the role of forest fragments as refuges mitigating ecological instability in cultivated landscapes. In the third part, the analysis is extended to a Mediterranean region, through the study of insect communities and predation rates in vineyards and adjacent woodlands. The influence of different vegetation characteristics, such as flower cover, herbaceous cover and plant species richness, is assessed. The results show that floral resources and plant diversity are key factors driving the abundance of auxiliary insects, particularly at the edge of the vineyard, where the spillover effect from the forest environment is most marked. The use of sentinel prey shows higher predation rates in woodland areas, with positive effects extending to vineyard plots, suggesting a contribution from semi-natural habitats to biological control. Overall, this thesis highlights the importance of vegetation quality and the spatial configuration of the landscape in structuring insect communities and providing ecosystem services. Forest fragments enhance biodiversity and promote ecological interactions beyond their boundaries, although these effects remain spatially limited and modulated by habitat structure and cultivation practices. By integrating functional and comparative approaches between regions, this work highlights the need for conservation and restoration strategies aimed at preserving habitat quality and functional connectivity in agricultural landscapes. The results provide concrete guidelines for designing sustainable agricultural systems that reconcile production and biodiversity conservation.