A WASPS REARING MODEL TO ENHANCE VINEYARD BIODIVERSITY AND ITS ROLE AS BIOINDICATOR

The primary objective of this thesis was to assess the effectiveness of a rearing method designed to support wasp colonies while preserving their natural de- velopmental processes. This method utilized common gardening pots, referred to in this study as shelters, to provide a controlled yet adaptable environment for colony establishment and management. To evaluate the method, a total of 30 Polistes dominula colonies were monitored over a four-month period (sum- mer 2022) under three distinct conditions: (i) 10 colonies that spontaneously established themselves within the shelters, (ii) 10 colonies originally founded within shelters and subsequently relocated along with them to new sites, and (iii) 10 colonies sampled from natural environments and transplanted into shel- ters. Statistical analyses of individual counts per nest were performed to assess colony growth and stability across conditions. The results showed no significant differences in growth patterns between relocated colonies and those that sponta- neously established themselves within the shelters. These findings indicate that the resilience of P. dominula allows for successful colony rearing and relocation without negatively impacting development. This supports the feasibility of the proposed rearing method for both experimental and applied purposes, including field-based ecological studies and conservation strategies. The second part of this project aimed to evaluate whether Polistes dominula colonies, reared using the tested method, could directly transport a yeast strain onto vineyard grapes. To assess their effectiveness as microbial vectors, the wasps were fed with the Saccharomyces cerevisiae 1014 strain, under field con- ditions at the experimental site. To track the presence of the inoculated strain in grape samples collected after wasp exposure, two selective media (5-FOA and 5,5,5-TFL) were used. Additionally, metagenomic analyses were performed on the collected samples to investigate the potential impact of the wasps and the inoculated strain on the fungal microbiota composition of the grapes. The pres- ence of S. cerevisiae 1014 was confirmed in grapes from the experimental row exposed to the wasps fed with the selected strain, as determined by selective me- dia. Furthermore, fungal microbiota analysis revealed a microbial composition trend consistent with the findings of the Ca’Marcanda study. The third objective of this project was to assess the potential use of Polistes dominula larval feces as bioindicators for detecting variations in heavy metal concentrations (Cd, Pb, Ni, and Hg). This approach aimed to determine whether meconia could serve as an effective tool for monitoring environmental contami- nation. To achieve this, samples were collected from P. dominula colonies reared under three different conditions: (i) a controlled laboratory environment (reference group), (ii) an urban area (Marescialli and Brigadieri School, Florence), and (iii) an agricultural area (a private farm in Pratolino, Florence). Colonies were monitored from early May to August, after which meconia were collected at the end of the summer. Heavy metal concentrations in the samples were quan- tified using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP- OES). The analysis revealed significant differences in heavy metal accumulation among the three study sites. Nickel (Ni) and cadmium (Cd) concentrations were statistically higher in both the urban and agricultural sites compared to the laboratory-reared colonies. Lead (Pb) levels were found to be significantly elevated in the agricultural area. In contrast, mercury (Hg) concentrations did not show significant variation among the three groups. These findings suggest that P. dominula meconia could serve as a promising bioindicator for assessing environmental contamination by heavy metals.