Pollinators play a crucial role in ecosystems globally, ensuring the seed production of most flowering plants. They are threatened by global changes and knowledge of their distribution at the national and continental levels is needed to implement efficient conservation actions, but this knowledge is still fragmented and/or difficult to access. As a step forward, we provide an updated list of around 3000 European bee and hoverfly species, reflecting their current distributional status at the national level (in the form of present, absent, regionally extinct, possibly extinct or non‐native). This work was attainable by incorporating both published and unpublished data, as well as knowledge from a large set of taxonomists and ecologists in both groups. After providing the first National species lists for bees and hoverflies for many countries, we examine the current distributional patterns of these species and designate the countries with highest levels of species richness. We also show that many species are recorded in a single European country, highlighting the importance of articulating European and national conservation strategies. Finally, we discuss how the data provided here can be combined with future trait and Red List data to implement research that will further advance pollinator conservation.

In this paper we analyzed environmental differentiation of closely related species from the Merodon ruficornis group. By applying principal component analysis (PCA) and environmental niche modelling (ENM)-based techniques, we estimated the level of niche divergence of closely related species. Our results indicate that ecology has an important role in the diversification process in related species from the M. ruficornis group. Distribution patterns of all analyzed species are mainly affected by the limiting effects of the temperature of the coldest quarter and month, as well as by the precipitation of the wettest and driest quarters. Our results demonstrated that among all related species, with the exception of M. ovaloides, overall or partial divergence in environmental space is present. Importantly, the results indicate that the environmental niches of all endemic species are restricted to smaller parts of the environmental space. In the case of niche overlap, the niches of endemic species are placed along the border of the realized niche of the widespread related species. For species in which distribution is not limited by geographical barriers, environmental preferences could be considered as limiting factors for further expansion, as in the case of M. alexandri, a lowland species with very strict climatic adaptations. Knowledge about the environmental factors that might influence the diversification process can provide an explanation for the high diversity in other Merodon species groups.

While several recent studies have focused on global insect population trends, all are limited in either space or taxonomic scope. As global monitoring programs for insects are currently not implemented, inherent biases exist within most data. Expert opinion, which is often widely available, proves to be a valuable tool where hard data are limited. Our aim is to use global expert opinion to provide insights on the root causes of potential insect declines worldwide, as well as on effective conservation strategies that could mitigate insect biodiversity loss. We obtained 753 responses from 413 respondents with a wide variety of spatial and taxonomic expertise. The most relevant threats identified through the survey were agriculture and climate change, followed by pollution, while land management and land protection were recognized as the most significant conservation measures. Nevertheless, there were differences across regions and insect groups, reflecting the variability within the most diverse class of eukaryotic organisms on our planet. Lack of answers for certain biogeographic regions or taxa also reflects the need for research in less investigated settings. Our results provide a novel step toward understanding global threats and conservation measures for insects.

Spatial and temporal differences in landscape patterns are of considerable interest for understanding ecological processes. In this study, we assessed habitat quality by using the Syrph The Net database and data on decreasing species richness over a 25-year period for the two largest phytophagous hoverfly genera (Merodon and Cheilosia). Furthermore, within this time frame, we explored congruence between ecological responses (species richness and Biodiversity Maintenance Function for these two genera) and landscape structural changes through correlation analysis. Our results indicate that landscapes have experienced changes in aggregation, isolation/connectivity and landscape diversity, with these parameters being significantly correlated with Cheilosia species richness loss and habitat quality. We conclude that the genus Cheilosia is a good bioindicator that can highlight not only the current quality of an area but also temporal changes in landscape patterns.