Experimental evolution with an insect model reveals that male homosexual behaviour occurs due to inaccurate mate choice

Sales, Kris, Trent, Thomas, Gardner, Jessie, Lumley, Alyson J., Vasudeva, Ramakrishnan ORCID: https://orcid.org/0000-0002-3831-0384, Michalczyk, Łukasz, Martin, Oliver Y. and Gage, Matthew J. G. (2018) Experimental evolution with an insect model reveals that male homosexual behaviour occurs due to inaccurate mate choice. Animal Behaviour, 139. 51–59. ISSN 0003-3472

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Abstract

The existence of widespread male same-sex sexual behaviour (SSB) is puzzling: why does evolution allow costly homosexual activity to exist, when reproductive fitness is primarily achieved through heterosexual matings? Here, we used experimental evolution to understand why SSB occurs in the flour beetle Tribolium castaneum. By varying the adult operational sex ratio across 82–106 generations, we created divergent evolutionary regimes that selected for or against SSB depending upon its function. Male-biased (90:10 M:F) regimes generated strong selection on males from intrasexual competition, and demanded improved ability to locate and identify female mates. By contrast, Female-biased regimes (10:90 M:F) generated weak male–male competition, and relaxed selection on mate-searching abilities in males. If male SSB functions through sexually selected male–male competition, it should be more evident within Male-biased regimes, where reproductive competition is nine times greater, than in the Female-biased regimes. By contrast, if SSB exists due to inaccurate mate choice, it should be reduced in Male-biased regimes, where males experience stronger selection for improved mate finding and discrimination abilities than in the Female-biased regime, where most potential mating targets are female. Following these divergent evolutionary regimes, we measured male engagement in SSB through choice experiments simultaneously presenting female and male mating targets. Males from both regimes showed similar overall levels of mating activity. However, there were significant differences in levels of SSB between the two regimes: males that evolved through male-biased operational sex ratios located, mounted and mated more frequently with the female targets. By contrast, males from female-biased selection histories mated less frequently with females, exhibiting almost random choice between male and female targets in their first mating attempt. Following experimental evolution, we therefore conclude that SSB does not function through sexually selected male–male competition, but instead occurs because males fail to perfectly discriminate females as mates.

Item Type:	Article
Uncontrolled Keywords:	experimental evolution,homosexual,mating,sexual selection,tribolium castaneum
Faculty \ School:	Faculty of Science > School of Biological Sciences Faculty of Science > School of Environmental Sciences
UEA Research Groups:	Faculty of Science > Research Centres > Centre for Ecology, Evolution and Conservation Faculty of Science > Research Groups > Organisms and the Environment
Depositing User:	Pure Connector
Date Deposited:	06 Apr 2018 08:30
Last Modified:	12 May 2023 12:30
URI:	https://ueaeprints.uea.ac.uk/id/eprint/66686
DOI:	10.1016/j.anbehav.2018.03.004

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