Journal of Insect Behavior

, Volume 26, Issue 3, pp 440–452

Alternate Reproductive Tactics in an African Dung Beetle, Circellium bacchus (Scarabeidae)

Article

DOI: 10.1007/s10905-012-9365-1

Cite this article as:
Reynolds, C. & Byrne, M.J. J Insect Behav (2013) 26: 440. doi:10.1007/s10905-012-9365-1

Abstract

Male-male competition is recognized as a potent force of sexual selection. When intra-sexual competition is strong then selection theory predicts that alternative male phenotypes will evolve. Circellium bacchus is a large, hornless, ball-rolling dung beetle with extensive variation in size and subject to intense male-male contest competition. We proposed that small male C. bacchus, which are unlikely to be successful in male contest competition, would adopt the alternative reproductive tactic of sneaking copulations. This alternative tactic is likely to influence not only behavior, but morphology with an expectation that sneaking males would invest more resources in testes development. Investigation of testis allometry revealed that smaller male C. bacchus beetles had relatively larger testes than their bigger conspecifics. Furthermore, as resources may be limited during larval development, differential investment in testes development should result in adult male beetles either competing for fertilizations or for access to mates. This is seen in C. bacchus as two alternate male phenotypes; smaller beetles with a relatively low body mass invest proportionately more in testes development compared to larger, heavier form in which testes size does not scale with condition. To our knowledge this study provides the first investigation of alternative phenotypes in the reproductive tactics of a ball-rolling dung beetle species.

Keywords

Alternative reproductive tacticsmale-male competitionsperm competitionoperational sex ratioCircellium bacchustestissneaks

Copyright information

© Springer Science+Business Media New York 2012

Authors and Affiliations

  1. 1.School of Animal, Plant and Environmental SciencesUniversity of the WitwatersrandWitsSouth Africa
  2. 2.Organization for Tropical Studies, South Africa ProgramSkukuzaSouth Africa
  3. 3.Percy FitzPatrick Institute of African Ornithology, DST/NRF Centre of ExcellenceUniversity of Cape TownCape TownSouth Africa