Cross-species correlation between queen mating numbers and worker ovary sizes suggests kin conflict may influence ovary size evolution in honeybees
During social evolution, the ovary size of reproductively specialized honey bee queens has dramatically increased while their workers have evolved much smaller ovaries. However, worker division of labor and reproductive competition under queenless conditions are influenced by worker ovary size. Little comparative information on ovary size exists in the different honey bee species. Here, we report ovariole numbers of freshly dissected workers from six Apis species from two locations in Southeast Asia. The average number of worker ovarioles differs significantly among species. It is strongly correlated with the average mating number of queens, irrespective of body size. Apis dorsata, in particular, is characterized by numerous matings and very large worker ovaries. The relation between queen mating number and ovary size across the six species suggests that individual selection via reproductive competition plays a role in worker ovary size evolution. This indicates that genetic diversity, generated by multiple mating, may bear a fitness cost at the colony level.
KeywordsSocial evolution Levels of selection Worker reproduction Caste divergence Reproductive conflict Ovarioles
We thank Prachaval Sukumalanand, Deborah Smith, Gudrun and Nikolaus Königer, Evelyn Hunggims, Michael Burgett, and all members of the social insect group at UNCG for their kind practical support. We also thank Gudrun and Nikolaus Königer and four anonymous reviewers for their comments on a previous version of the manuscript. This work was supported financially by the National Institute of Food and Agriculture, US Department of Agriculture, under Agreement No. 2010-65104-20533, the National Institute of Aging (#PO1 AG22500), the National Science Foundation (#0615502), and the National Research University Project of Thailand's Office of the Higher Education Commission.
- Chaud-Netto J, Bueno OC (1979) Number of ovarioles in workers of Apis mellifera adansonii and Apis mellifera ligustica: a comparative study. J Apicult Res 18:260–263Google Scholar
- Daly HV, Balling SS (1978) Identification of Africanized honeybees in the Western hemisphere by discriminant analysis. J Kans Entomol Soc 51:857–869Google Scholar
- Oldroyd BP, Wongsiri S (2006) Asian honey bees: biology, conservation and human interactions. Harvard University Press, CambridgeGoogle Scholar
- Oster GF, Wilson EO (1978) Caste and ecology in the social insects. Princeton University Press, PrincetonGoogle Scholar
- Snodgrass RE (1956) Anatomy of the honey bee. Comstock, IthacaGoogle Scholar
- Velthuis HHW, Clement JL, Morse RA, Laigo FM (1971) The ovaries of Apis dorsata from the Philippines. J Apic Res 10:63–66Google Scholar