Nectar in oak savannas: implications for butterfly conservation.

Area of Science:

• Ecology
• Conservation Biology
• Entomology

Background:

• Oak savanna restoration often focuses on the Karner blue butterfly (Plebejus melissa samuelis), a federally endangered species.
• Existing research correlates butterfly populations with nectar plant abundance, but nectar quality is less understood.

Purpose of the Study:

• To compare floral nectar resources across oak savanna sites based on Karner blue butterfly occupancy.
• To assess the influence of nectar volume, sugar concentration, and seasonal availability on habitat restoration effectiveness.

Main Methods:

• Quantified floral abundance, nectar volume, and sugar concentration for 22 plant species across 15 sites.
• Calculated mean nectar availability per stem and estimated seasonal nectar sugar contribution.
• Measured environmental variables and compared nectar resources between occupied and unoccupied sites.

Main Results:

• Species identity significantly predicted nectar volume and sugar concentration (3.06%–61.26% Brix).
• Rubus flagellaris and Ceanothus americanus were key spring and summer nectar sugar sources, respectively.
• Sites with Karner blue butterfly occupancy had 11 times more spring nectar sugar than unoccupied sites.

Conclusions:

• Nectar characteristics, beyond mere abundance, are crucial for Karner blue butterfly habitat.
• Understanding seasonal nectar distribution and quality can enhance oak savanna restoration and pollinator conservation.
• This research provides critical data for effective management of imperiled habitats.