Effects of Honey Bee (Apis mellifera) Intracolonial Genetic Diversity on the Acquisition and Allocation of Protein

摘要

Honey bees (Apis mellifera) are the most economically important insect pollinator of agricultural crops in the United States. Honey bee colonies are required for pollination of approximately one-third of the nation’s fruit, vegetable, nut, and forage crops, with an estimated annual value in the billions of dollars. The economic value of a honey bee colony comes from its population size, as large colonies provide the necessary foraging force required for large-scale crop pollination services. A major component of colony strength is its genetic diversity, a consequence of the reproductive mating strategy of the queen known as polyandry. Despite some inherent risks of multiple mating, several studies have demonstrated significant advantages of intracolonial genetic diversity for honey bee colony productivity. Colony-level benefits include better disease resistance, more stable brood nest thermoregulation, and greater colony growth. Instrumental insemination of honey bee queens is a technique to precisely control queen mating, and thereby creates the opportunity to investigate the effects of intracolonial genetic diversity on colony performance. In this dissertation, I first consider the effects of intracolonial genetic diversity on pollen foraging using colonies headed by queens which were instrumentally inseminated with either one or twenty drones to generate colonies of very high or very low intracolonial genetic diversity, respectively. I found that colonies with high intracolonial genetic diversity amass significantly more pollen and rear more brood than colonies with low intracolonial genetic diversity. Of particular interest, colonies with low intracolonial genetic diversity collected a significantly greater variety of pollen types. I discuss these results in the context of scouting and recruiting, and suggest a more efficient foraging strategy exists among genetically diverse colonies. While intracolonial genetic diversity is positively correlated with collected pollen, its effect on the colony’s ability to process and distribute inbound protein resources is unknown. Again using colonies headed by queens instrumentally inseminated with either one or twenty drones, I studied the effects of intracolonial genetic diversity on pollen consumption and digestion by nurse bees, as well as protein allocation among nestmates by assessing total soluble protein concentration of late instar larvae, and total soluble hemolymph protein concentration in both nurses and pollen foragers. I found that nurse bees from colonies with high intracolonial genetic diversity consume and process more protein than nurses from colonies with low intracolonial genetic diversity, even when given equal access to protein resources. Further, both forager hemolymph protein concentrations and larval total protein concentrations were higher among the colonies with high intracolonial genetic diversity. My findings suggest that protein processing and distribution within a honey bee colony is affected by the social context of the hive. I discuss “worker policing”, and the role of nurse bees in modulating the foraging effort. Finally, I assess the standing genetic variability among several colonies sourced from different genetic and geographic locations. Using microsatellite DNA from workers sampled from each colony, I determined allelic richness, gene diversity, and effective mating frequency for each genetic line. I found differences in all three metrics between lines, and for one line in particular, there was no correlation with genetic variation and effective mating frequency, suggesting non-random mating. My results showed very different levels of intracolonial genetic diversity among naturally mated queens. Because of its impact on colony performance, the importance of maintaining genetic diversity in breeding populations is discussed.