Biodiversità degli Imenotteri impollinatori in Sicilia (Italia) e analisi delle reti di impollinazione

Resumo

Pollinators are a decisive component in promoting biodiversity because they provide ecosystem services by increasing the reproduction of wild plants as well as guaranteeing food security deriving from the production of many agricultural crops. Among pollinators, bees (Hymenoptera, Apoidea) constitute the most important taxonomic group as they are obliged to collect pollen and nectar to feed the larvae. At the same time, they contribute to the reproduction of most angiosperms. The areas with a Mediterranean climate are undoubtedly hotspots of biodiversity for Apoidea. Italy, due to its particular geographical position in the heart of the Mediterranean, together with the geomorphological and orographic complexity that determine a great diversity of climates and natural environments, is one of the European countries with the largest number of bee species. However, large areas of the country have not yet been thoroughly investigated for bee communities, and there is a lack of studies concerning the quantitative interactions between bees and plants in such areas. This is particularly interesting considering the recent global declines of bee populations due to different anthropogenic pressures. This study provides a contribution to the knowledge of bees in two areas of Eastern Sicily with different degrees of anthropic impact ("La Rocca di Buticari" Suburban Park in the territory of Nizza di Sicilia and the Oriented Natural Reserve of Fiumedinisi and Monte Scuderi, on the Peloritani mountains), in order to lay the foundations for identifying conservation strategies. The study presented here consists of two parts: 1) identification of Apoidea through molecular techniques (DNA barcoding) in order to confirm this method as appropriate in bee biodiversity studies, and 2) analysis of ecological networks between species of bees collected and the plants they visited, in order to characterize the ecological role of bees in the investigated environments. The molecular analyses included amplification by polymerase chain reaction (PCR) and sequencing of the molecular marker cox1. The potentiality of the fragment was tested comparing with the sequences available in the databases (Genbank, NCBI) and the result of the data demonstrated the effective applicability of the method, successfully contributing to the identification of most bee species, and producing new sequences for species for which they are currently lacking. Bee communities have been characterized both in terms of diversity and abundance, and as components of bipartite ecological networks. The analysis showed that Buticari is a more diverse site for bee species than the natural area of Fiumedinisi, and that the network structures observed at both sites are highly specialized, modular and non-nested, with special differences emerging if the whole communities (strongest specialization in the Fiumedinsi network) or only the interactions between plants and Bombus (strongest specialization in the Buricari network), a genus that was particularly rich in species during the study. This study has demonstrated rich communities of bees forming specialized and modular networks in a natural area of Eastern Sicily, confirming the high naturalistic value of the Fiumedinisi and Monte Scuderi Oriented Reserve and the large green area of the Suburban Park “La Rocca di Buricari”, in a manner consistent with what found in other gardens and urban parks. In the future, new and detailed studies on the bee communities of Sicily are expected, since this is an area of undoubted interest due to its insularity and high levels of biological diversity.