The nectar alkaloid, gelsemine, does not affect offspring performance of a native solitary bee, Osmia lignaria (Megachilidae)

Abstract.  1. The ecology and evolution of foliar-feeding insects are thought to be closely tied to plant secondary compounds. Although secondary compounds are also abundant in floral nectar, their role in mediating pollinator preference and performance remains relatively unexplored.
2. This study tested the effects of an alkaloid, gelsemine, found in the nectar of Carolina jessamine ( Gelsemium sempervirens L., Loganiaceae), on the performance of a native solitary bee ( Osmia lignaria lignaria Say, Megachilidae). Nectar gelsemine reduces visits from pollinators, including O. lignaria lignaria , and gelsemine is toxic to vertebrates and possibly non-native honey bees ( Apis mellifera L., Apidae). To test the hypothesis that the deterrent effects of nectar gelsemine reflect negative consequences for pollinator performance, O. lignaria lignaria offspring provisions were supplemented with nectar containing different gelsemine concentrations. Effects on larval development time, prepupa cocoon mass, adult emergence, and adult mass were measured.
3. Nectar gelsemine had no effect on any measure of offspring performance. Thus, although gelsemine deters foraging by adult bees, this behaviour did not optimize offspring performance under the experimental conditions of this study. In contrast, sugar added to nectar treatments increased offspring mass.
4. While adult pollinators may avoid nectar with secondary compounds, this could hinder offspring performance by reducing sugar in provisions if nectar is limiting in the environment. Preference-performance trade-offs, which are studied extensively with foliar herbivores, have seldom been tested for pollinating plant consumers. Future studies of nectar secondary compounds and insect pollinator preference and performance may help to integrate studies of foliage-consuming insect herbivores with nectar-consuming insect pollinators.