Genetic and Phenotypic Variation in Foraging Behavior of African and European Honey Bees

Arizona State University, Scottsdale AZ

Investigators

Abstract

Genetic and Phenotypic Variation in Foraging Behavior of African and European Honey Bees Principle Investigators: Jennifer H. Fewell and Jon F. Harrison, Arizona State University A fundamental question in integrative biology is how genetic variation relates to variation in an animal's survival and reproductive strategies. One way to answer this is to determine the genetic basis for behavioral differences between animal populations and then assess the ecological effects of those differences. This project examines foraging strategy differences between neotropical African-derived (Apis mellifera scutellata) and European (Apis mellifera ligustica) honey bees. It addresses to the questions of: (1) how genetic variation between African and European workers influences foraging strategy, and (2) how variation in worker foraging strategy affects differences in colony growth rates between the two subspecies. Population-level research suggests that African honey bees out-compete European bees primarily through faster rates of colony growth and reproduction (swarming). Because honey bees are social insects, these differences in colony strategy are generated by collective differences in the behavior of the colony's individual workers. Prior research by the investigators suggests that a major behavioral difference between African and European workers is in foraging. African workers show a higher tendency than European workers to collect pollen. Because pollen is the primary food source for developing brood, this difference can have profound effects on colony growth. The first objective of this research is to understand the mechanisms producing individual differences in pollen and nectar foraging. The investigators will test the hypothesis that differences in resource choice between African and European foragers are driven by differences in their sensitivity to stimuli affecting pollen collection. They will determine whether co-fostered African workers respond more readily to stimuli known to affect pollen foraging, and examine differences between African and European workers in genomic regions (quantitative trait loci or QTL's) known to be associated with pollen foraging behavior in European bees. Preliminary data also suggest that African and European workers differ in work effort during foraging, and that this variation may be mediated by differences in metabolic capacity. The second objective is to test the hypothesis that variation in metabolic rate between African and European honey bees is genetically based, and is linked to differences in resource preference and foraging effort. The researchers will compare metabolic rates, foraging load sizes and foraging rates of co-fostered African, European and hybrid workers to determine how these traits are inherited. Then, quantitative trait locus (QTL) mapping will be performed to locate genomic regions influencing variation in flight metabolic rates. These will be compared to known loci affecting body size and preference for pollen versus nectar collection. The third objective is to determine whether variation in individual foraging behavior affects colony-level growth rates. The investigators will: (a) measure pollen intake rates and colony growth rates in African and European hives, and (b) experimentally manipulate the genotypes of the foragers in a hive (African versus European), to measure the effect of forager genotype on brood production. This research integrates behavior, physiology and genetics to generate a more complete understanding of the proximate mechanisms generating complex behavioral traits such as foraging. It also examines the consequences of individual behavioral differences on the ecological success of these competing subspecies.