ORIGINAL PAPER Intracolonial genetic diversity in honeybee (Apis mellifera) colonies increases pollen foraging efficiency Bruce J. Eckholm & Kirk E. Anderson & Milagra Weiss & Gloria DeGrandi-Hoffman Received: 14 October 2010 / Revised: 14 October 2010 / Accepted: 2 November 2010 / Published online: 18 November 2010 # Springer-Verlag 2010 Abstract Multiple mating by honeybee queens results in colonies of genotypically diverse workers. Recent studies have demonstrated that increased genetic diversity within a honeybee colony increases the variation in the frequency of tasks performed by workers. We show that genotypically diverse colonies, each composed of 20 subfamilies, collect more pollen than do genotypically similar colonies, each composed of a single subfamily. However, genotypically similar colonies collect greater varieties of pollen than do genotypically diverse colonies. Further, the composition of collected pollen types is less similar among genotypically similar colonies than among genotypically diverse colonies. The response threshold model predicts that genotypic subsets of workers vary in their response to task stimuli. Consistent with this model, our findings suggest that genotypically diverse colonies likely send out fewer numbers of foragers that independently search for pollen sources (scouts) in response to protein demand by the colony, resulting in a lower variety of collected pollen types. The cooperative foraging strategy of honeybees involves a limited number of scouts monitoring the environment that then guide the majority of foragers to high quality food sources. The genetic composition of the colony appears to play an important role in the efficiency of this behavior. Keywords Intracolonial genetic diversity . Polyandry . Genetic influence on pollen foraging Introduction Honeybee (Apis mellifera) queens mate with multiple males, a reproductive strategy known as polyandry. Evolutionary reasons for the behavior are not entirely understood given the potential risks of multiple mating, which include exposure to predation and disease (Sherman et al. 1988), as well as energetic costs. Further, the reduction in nestmate relatedness with increasing mating frequency (Palmer and Oldroyd 2000) seems counter to eusociality, as it negates the advantage of kin selection, a well accepted explanation for eusocial evolution (Hamilton 1964). Interestingly, a recent hypothesis based on a comprehensive phylogenetic analysis suggests that polyandry is likely a derived trait that evolved either after or concurrently with eusociality (Hughes et al. 2008). While uncommon, polyan- dry occurs repeatedly among the eusocial Hymenoptera (Boomsma and Ratnieks 1996; Strassmann 2001), suggest- ing the net effect of this mating strategy is adaptive. In particular, all species of the genus Apis exhibit extremely high levels of polyandry (Oldroyd et al. 1998; Strassmann 2001). Among the many hypotheses put forward to explain the adaptive significance of polyandry (e.g., Ridley 1988; Keller and Hudson 1994; Cole and Wiernasz 1999; Jennions and Petrie 2000; Crozier and Fjerdingstad 2001; Strassmann 2001; Tarpy and Page 2002; Kraus et al. 2004; Schlüns et al. Communicated by R. Moritz Electronic supplementary material The online version of this article (doi:10.1007/s00265-010-1108-8) contains supplementary material, which is available to authorized users. B. J. Eckholm (*) : M. Weiss Department of Entomology, University of Arizona, Tucson, AZ 85721, USA e-mail: beckholm@ag.arizona.edu K. E. Anderson : G. DeGrandi-Hoffman Carl Hayden Bee Research Center, USDA-ARS, 2000 East Allen Road, Tucson, AZ 85719, USA Behav Ecol Sociobiol (2011) 65:1037–1044 DOI 10.1007/s00265-010-1108-8