Nectar traits variability in Buglossoides purpurocaerulea (L.) I.M.Johnst

Floral nectar is the main reward offered to pollinators. The behaviour and efficacy of the pollinators themselves are affected by nectar traits, but the latter may vary within the same plant and even the same flower, depending on intrinsic and extrinsic factors (Schaeffer et al. 2016, Palmer‐Young et al. 2019). In this study, we investigated whether the nectar of Buglossoides purpurocaerulae (L.) I.M.Johnst. (Boraginaceae, Lithospermae) changed through functionally different floral stages and after insect visits.B. purpurocaerulea is a self‐incompatible plant relying on pollinators for its sexual reproduction. Flowers show incomplete proterogyny and no hercogamy, thus self‐pollination could potentially occur. The studied population is situated close to Bologna, in the protected area SIC‐ZPS IT4050001. Nectar samples were collected from different floral stages and from both bagged and unbagged flowers. HPLC analyses were performed to investigate amino acid and sugar composition.We found that nectar volume and sugar abundance are affected by floral phenology as well as by insect visitation. When visits are prevented, the older flowers contain more nectar but lower sugar concentration. These results suggest nectar sugar reabsorption in unvisited flowers. At the female stage, nectar shows a lower sugar content but as concentrated as in the other phenological stages. In contrast, the amino acid profile does not change during the flower lifespan, being relatively rich already in the bud. In particular, the high concentration of β‐alanine, which is likely to affect pollinator preference because of its involvement in functional flight muscles, possibly explains why the female stage is already attractive to insects (Bogo et al. 2019