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An invasion of cheats

So-called ‘nuptial’ gifts – often consisting of food – are typically given to females by males as part of courtship and copulation rituals in many species.

By manipulating the gifts that female insects receive during copulation, University of St Andrews researchers have now shown that female preferences can be exploited by males who are “cheating” on their reproductive investment by presenting easily obtainable, but inedible token gifts.

Gift-giving during courtship and copulation occurs across the animal kingdom, including humans. Nuptial gifts can range from valuable nutritious food items to inedible tokens such as leaves or silk balloons. Gift-giving is of clear benefit to females when gifts are nutritious (and therefore valuable), but why females of some species require an inedible and worthless gift remains unexplained.

In experiments reported in Current Biology this week, Dr Natasha LeBas and colleague Dr Leon Hockham removed the valuable (edible) nuptial gift that male empidid dance flies normally provide their female partner, and replaced the gift with either a large edible gift or an inedible cotton ball token that resembles tokens given by other empidid fly species. The researchers found that, while pairs copulated longest following presentation of a large edible gift, the females receiving the worthless cotton ball token were sufficiently tricked to allow males to copulate for as long as when the males provided a small nutritious gift. Males who substitute highly visible, but easily obtainable and worthless gifts, may therefore be able to invade a population of genuine gift-giving males.

Dr LeBas said, “The research demonstrates that females may be susceptible to the invasion of so- called male cheating behaviour and suggests that the evolution of worthless gift-giving could arise though males’ sensory exploitation of female preferences for nutritious gifts”.

ENDS

NOTE TO EDITORS

Image illustrating the above available from Claire Grainger – contact details below. It should be credited to both the authors and the journal – LeBas and Hockham/Current Biology 2005.

Dr LeBas is currently working in Australia and is available on telephone ++ 61 8 9381 5340 or ++ 61 8 9380 2003. Dr Hockham is not available.

Issued by Beattie Media On behalf of the University of St Andrews For more information, please contact Claire Grainger, Press Officer – 01334 462530, 07730 415 015 or cg24@st-andrews.ac.uk; Ref: press releases/LEBAS nuptialgifts View the latest University news at http://www.st-andrews.ac.uk

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