Unused railway lines for conservation of pollinators in the intensively managed agricultural landscape

Abstract

Pollinating insects are under high human pressure due to agricultural intensification and urbanization. Although many research and conservation projects have been applied worldwide, there is still a need for a comprehensive approach that meets local conditioning and capabilities. This paper investigated the composition, abundance, richness, alpha, beta, and gamma-diversity of pollinators between unused railway embankments and semi-natural grasslands. On 50 study sites (25 sites in unused railways and 25 their reference on grasslands), we collected data on the abundance, species richness and species diversity of bees, butterflies, and hoverflies. We conducted five samplings yearly (April–September) for two years, 2017–2018. To assess differences in abundance, species richness, alpha and beta diversity of pollinators between unused railways and controls, we used generalized linear mixed models (GLMM). To compare the composition of pollinator species, we applied non-metric multidimensional scaling (NMDS). Abundance, species richness, and Shannon-Wiener diversity index of all three groups of pollinators were significantly higher in unused railway lines than in control grasslands. Pollinator communities were more constant in unused railway lines than in grasslands. The NMDS analysis highlighted the importance of these structures for bee, butterfly and hoverfly communities, which were a subset of grassland species, but were more abundant. We indicated the highest total taxonomic beta-diversity for bees, butterflies, and hoverflies and species turnover for bees and butterflies in control grassland compared with unused railway lines. The taxonomical nestedness was significantly higher in unused railways lines for bees and butterflies than in control grasslands. In the case of hoverflies, we did not found any significant differences in species turnover and nestedness. Unused railway lines may act as a conservation tool for pollinator communities in intensively managed farmland and complement the declining semi-natural habitats.