Originally published as Genetics Published Articles Ahead of Print on September 19, 2005.

Genetics, Vol. 172, 243-251, January 2006, Copyright © 2006
doi:10.1534/genetics.105.046490

The Genetic Architecture of Sucrose Responsiveness in the Honeybee (Apis mellifera L.)

Olav Rueppell*,1, Sathees B. C. Chandra{dagger}, Tanya Pankiw{ddagger}, M. Kim Fondrk§, Martin Beye**, Greg Hunt{dagger}{dagger} and Robert E. Page§§

* Department of Biology, University of North Carolina, Greensboro, North Carolina 27402, {dagger} Department of Biological, Chemical and Physical Sciences, Roosevelt University, Chicago, Illinois 60605, {ddagger} Department of Entomology, Texas A&M University, College Station, Texas 77843, § Department of Entomology, University of California, Davis, California 95616, ** Institute for Zoology, Biozentrum, Martin Luther University, Halle-Wittenberg 06120 Halle, Germany, {dagger}{dagger} Department of Entomology, Purdue University, West Lafayette, Indiana 47907 and §§ School of Life Sciences, Arizona State University, Tempe, Arizona 85287-4501

1 Corresponding author: Department of Biology, UNCG, 1000 Spring Garden St., Greensboro, NC 27402.
E-mail: olav_rueppell{at}uncg.edu

One of the best examples of a natural behavioral syndrome is the pollen-hoarding syndrome in honeybees that ties together multiple behavioral phenotypes, ranging from foraging behavior to behavioral ontogeny and learning performance. A central behavioral factor is the bees' responsiveness to sucrose, measured as their proboscis extension reflex. This study examines the genetics of this trait in diploid worker and haploid male honeybees (drones) to learn more about the genetic architecture of the overall behavioral syndrome, using original strains selected for pollen-hoarding behavior. We show that a significant proportion of the phenotypic variability is determined by genotype in males and workers. Second, our data present overwhelming evidence for pleiotropic effects of previously identified quantitative trait loci for foraging behavior (pln-QTL) and epistatic interactions among them. Furthermore, we report on three genomic QTL scans (two reciprocal worker backcrosses and one drone hybrid population) derived from our selection strains. We present at least one significant and two putative new QTL directly affecting the sucrose response of honeybees. Thus, this study demonstrates the modular genetic architecture of behavioral syndromes in general, and elucidates the genetic architecture of the pollen-hoarding behavioral syndrome in particular. Understanding this behavioral syndrome is important for understanding the division of labor in social insects and social evolution itself.