Exploring the beekeeping potential of Sanguisorba dodecandra Moretti: insect visitation, open pollination efficiency, and volatile profiles of honey and flowers.

Leoni V., Panseri S., Giupponi L, Loni A., Gianoncelli C., Giorgi A.

Sanguisorba dodecandra Moretti is endemic to the Italian Alps. It grows in very different habitats in contrast to most other endemics that tend to occupy specific niches. It is a resource for honeybees, but it is not clear if they or other insects act as the main pollinator. The volatile profile of S. dodecandra flowers has not been studied, nor its impact on the aroma of their respective honey. We investigated the volatile profiles of S. dodecandra flowers and honey, the insects visiting its inflorescences, and the seed set resulting from open pollination compared to insect exclusion treatments. S. dodecandra was mainly visited by Diptera, especially hoverflies, both in mid mountain (52.46%) and high mountain (41.12%) habitats. Open pollination resulted in a higher seed set (4.42 ± 3.14 seeds/cm) than from bagged inflorescences (0.96 ± 1.50 seeds/cm). Although bees were rarely recorded visiting S. dodecandra, pollen spectra of honey produced in the area where the endemic species grows showed its pollen and that of other plants increased when flowering of more attractive species, such as linden, declined. Terpenes were well represented in honey and flowers. Out of 104 compounds identified in honey containing S. dodecandra as an important component and 116 in the inflorescences only 15 were common to both. Some of these (e.g., rose oxide or jasmone) are characterized by a geranium-jasmine smell. Our study highlighted new aspects of the reproductive strategy of this endemic species, that is different from its more common relative, Sanguisorba officinalis L. Despite a floral morphology aligned with a wind pollination syndrome it may be an important resource for bees where it occurs.