Nectar resources for butterfly restoration
Several rare butterflies, including the federally listed Karner Blue, and Ohio state listed Frosted Elfin and Persius Dusky Wing, are native to oak savannas of Ohio’s Oak Openings. As an important biodiversity hotspot near migratory bird routes, this area is also likely to be important to migrating butterflies such as Monarchs. Restoration efforts have increased availability of some host plants for butterfly larvae, while land managers are increasing milkweed plantings to assist declining populations. However, minimal research has been done on the quality of native nectar resources. In a pilot survey in savanna and prairie openings across three field sites, we sampled flowers of 30 forbs previously reported or likely to be visited by these butterflies. We collected nectar from flowers from which pollinators had been excluded for 24 – 72 hours. Samples were analyzed for nectar volumes using microcapillary pipettes, while sugar concentrations and presence of amino acids were analyzed using a refractometer and ninhydrin tests, respectively.
We found substantial interspecific variation in nectar volume, concentration, and composition. Liatris spicata, Monarda punctata and Asclepias syriaca, often visited by both Karners and Monarchs, had more concentrated nectar per flower than Lantana, an ornamental commonly used to attract butterflies in gardens. Coreopsis lanceolata, currently infrequent in the region, had the highest amino acid concentration than all other species tested. Although studies of effects of nectar quantity and quality on butterfly fitness are needed to more fully evaluate the conservation value of these species, these results suggest oak savanna and prairie restoration plans consider increasing planting of selected species that are more likely to provide enriched nectar resources for adults.