Distinguishing feral and managed honey bees (Apis mellifera) using stable carbon isotope ratios

Efforts to protect the honey bee (Apis mellifera) against Varroa mite and other diseases as well as develop more efficient pesticides are hindered by the inability to effectively distinguish feral from managed honey bees. Feral honey bees have experienced intense natural selection for resistance to colony pests and parasites and may provide a strong source of resistance genes. Genetic testing is typically unreliable given often-extensive interbreeding between feral and managed colonies.  Here we report on a diagnostic test based on stable carbon isotope ratios that provides a more reliable method for identification of feral versus managed honey bees.  Carbon isotopes have long been used to determine honey adulteration with added sugars, and our method works on the same principle, based on the fact that managed colonies are nearly always fed some supplemental sugar.  We set up four types of experimental colony types: feral, managed with no supplemental feed, managed with supplemental feed, and managed with ¹³C labeled glucose added to supplemental feed.  Carbon isotopic ratios in the tissues of individuals were analyzed using IRMS. Although we continue to gather and analyze data, preliminary analyses suggest that colonies receiving supplemental feed have higher ratios of ¹³C to ¹²C, and therefore carbon isotopic signatures can be used to distinguish feral from managed honey bees.  We will also report on ongoing labeled-glucose experiments to distinguish the turnover time of supplemental-feeding induced isotopic signatures in honey bee colonies.