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La comprensione delle relazioni tra gli ecosistemi, la biodiversità e il benessere umano risulta cruciale per il raggiungimento di uno sviluppo sostenibile. Tuttavia, il capitale naturale e i servizi ecosistemici che da questo dipendono sono minacciati dalle attività umane e persistono significative lacune nella conoscenza scientifica riguardo l’impatto di queste attività sulla biodiversità e sulle interazioni ecologiche. Gli impollinatori emergono come un obiettivo prioritario di indagine, data la loro importanza nel garantire la sicurezza alimentare e la conservazione della biodiversità. Questa tesi adotta un approccio integrato per esplorare aspetti finora trascurati dell’ecologia degli impollinatori. Nello specifico, sono stati esaminati: i) l’influenza dell’uso del suolo e della temperatura sulla chimica di polline e nettare; ii) le ripercussioni della frammentazione del paesaggio e della diversità locale di specie floreali sulla qualità e composizione della dieta di Bombus terrestris; iii) l’impatto dell’impollinazione mediata da insetti sulla qualità commerciale e sul valore nutraceutico di semi e frutti. Il primo capitolo introduce un innovativo strumento per il campionamento del polline e fornisce un’analisi comparativa di diverse tecniche di campionamento di polline e nettare. Il nuovo approccio presentato è risultato avere una maggiore efficienza e precisione nel campionamento. La comparazione condotta, ha sottolineato la necessità di standardizzare le tecniche di campionamento per produrre dati affidabili e condivisibili. L’ultima parte del capitolo esplora gli impatti di uso del suolo e temperatura sulla chimica delle risorse fiorali. Polline e nettare campionati da specie selvatiche in siti distribuiti lungo gradienti di urbanizzazione e intensificazione agricola, sono stati analizzati. Sono state osservate significative riduzioni del contenuto di zuccheri nel nettare in ambienti agricoli e variazioni nel profilo fitochimico del polline lungo, In the contemporary pursuit of sustainable development, understanding the relationship among ecosystems, biodiversity, and human well-being is crucial. Natural capital and ecosystem services are jeopardized by various human-induced pressures. However, significant scientific knowledge gaps persist, especially concerning the impact of human activities on biodiversity and ecological interactions. Animal-mediated pollination emerges a compelling investigation target, given its pivotal role in food security and biodiversity conservation. This thesis adopts a comprehensive multi-level integrative approach to explore neglected facets of pollination ecology. Specifically, we investigated i) the influence of land use and temperature on pollen and nectar chemistry; ii) the repercussion of landscape fragmentation and local flower richness on the quality and composition of a generalist pollinator diet; iii) the impact of insect mediated pollination on the commercial quality and nutraceutical value of two crops. The first chapter introduces an innovative tool for pollen sampling and provides a comparative analysis of multiple pollen and nectar sampling techniques. The comparative investigation conducted emphasized the need for standardization of the sampling techniques to produce reliable and shareable data. These methodological advances facilitated the investigation of the impacts of land use and temperature on pollen and nectar chemistry. Flower resources sampled from 7 different meadows species at 16 sites, distributed along gradients of urbanization and agricultural intensification, were analysed. Significant effects of land use and temperature on nectar sugar content were observed. Untargeted metabolomic analyses further revealed substantial variation in the phytochemical profiles of pollen along gradients of landscape anthropization. The second chapter shifts the focus from plants to insects, investigating the nutritional profile and composition of the diet of a generalist

Plant biodiversity is crucial to satisfy the trophic needs of pollinators, mainly through nectar and pollen rewards. However, a few studies have been directed to ascertain the intraspecific variation of chemical features and the nutritional value of nectar and pollen floral rewards in relation to the alteration of landscapes due to human activities. In this study, by using an existing scenario of land use gradients as an open air laboratory, we tested the variation in pollen and nectar nutrient profiles along gradients of urbanization and agriculture intensity, by focusing on sugar, aminoacids of nectar and phytochemicals of pollen from local wild plants. We also highlighted bioactive compounds from plants primary and secondary metabolism due to their importance for insect wellbeing and pollinator health. We surveyed 7 different meadow species foraged by pollinators and common in the main land uses studied. The results indicated that significant variations of nutritional components occur in relation to different land uses, and specifically that the agricultural intensification decreases the sugars and increases the antioxidant content of flower rewards, while the urbanization is positively associated with the total flavonoid content in pollen. These effects are more evident in some species than in others, such as Lotus corniculatus L. (Fabaceae) and Malva sylvestris L. (Malvaceae), as shown by the untargeted metabolomic investigation. This study is crucial for understanding the nutritional landscape quality for pollinators in association to different land uses and sets a base for landscape management and planning of pollinator-friendly strategies by improving the quality of plant rewards to provide benefits to pollinator health in various environmental contexts.

Urbanization gradients influence both landscape and climate and provide opportunity for understanding how plants and pollinators respond to artificially driven environmental transitions, a relevant aspect for the ecosystem service of pollination. Here, we investigated several aspects of pollination along an urbanization gradient in landscape and climate. We quantified wild hoverfly and bee abundances with trapping, standing crop of nectar with spectrophotometer, and the pollen transported by flower visitors with DNA metabarcoding, in 40 independent sites from semi-natural to built-up areas in Northern Italy. Direct and indirect effects were fitted considering landscape and climate variables. Linear and nonlinear relationships were detected along the urbanization gradient. Pollinator abundances increased quadratically and peaked at 22% of impervious cover with an 81% growth, and they decreased with green-patch distance by 37% and urban park largeness by 60%. This indicates that pollinators are more abundant at intermediate levels of urbanization. Climatically, pollinators diminished by up to 46% in areas with low spring-summer temperature seasonality: urban areas likely posing thermic stress. Furthermore, the sugar mass available in nectar increased by 61% with impervious cover and by 79% with precipitations, indicating that city nectars were less consumed or flowers more productive. Furthermore, the species richness of pollen decreased by 32% in highly urbanized areas, and contained a high incidence of exotic plants, hinting for anthropized, simplified plant communities. Synthesis and applications. Urbanization influences pollinator abundances, nectar resources and transported pollen in direct and indirect ways. Pollinators are negatively affected by a thermally harsh climate in highly urbanized areas with isolated green areas and large parks. Suburban landscapes demonstrated the highest pollinator presence. In the city core, flowers contained more nectary sugar in