Ornamental roses for conservation of leafcutter bee pollinators

Pollinator conservation is a global priority. Efforts are taken to restore pollinators by improving flower resources, a crucial driver of pollinator diversity and population growth. It helped gardening and landscaping supply chains, which introduced lists of bee-friendly plants and bee hotels, yet, desirable results seem distant. One shortcoming of the present schemes is that they lack a cohesive planning for nesting opportunities and nesting provisions for wild solitary bees, the crucial pollinators of crop and wild plants. We tested whether the world’s popular ornamental plant, rose (Rosa chinensis Jacq.)—a hitherto unlisted bee-friendly plant—can aid in conserving leafcutter bees, which require fresh leaves for constructing nest cells. We surveyed 2360 rose plants in 136 sites in rural and urban places and lowlands and highlands of south (8°N–12°N) and northeastern India (26°N–27°N) for the characteristic notches the bees leave on foraged leaves. We reared brood constructed with rose and non-rose leaves to examine the brood success rate. About a quarter of all the roses surveyed had the notches of leafcutter bees on the leaves. However, the proportion of cut roses varied considerably among sites. Bees used roses much higher in urban areas and lowlands than in rural areas and highlands. The selection of plants was negatively associated with pesticide application. The brood success rate was 100% for the brood that was constructed by the leaves of rose and non-rose plants. Rose flowers do not support bees, but rose leaves indeed do. We recommend rose plants in leafcutter bee conservation and restoration schemes, particularly in urban environment.