Spiteful soldiers and sex ratio conflict among parasitoid wasps

April 3, 2007

The social insects provide some of the most fascinating examples of altruism in the natural world, with sterile workers sacrificing their own reproduction for the greater good of the colony. Research carried out in Canada and the United Kingdom reveals that, for a peculiar group of parasitic wasps, this sacrifice is more sinister.

For years the function of sterile 'soldier' larvae in polyembryonic parasitoid wasps has been controversial. Traditionally, these have been viewed as bringing a benefit to their broodmates as a whole, for example by protecting them from attack by other species of parasitoids. More recently, it has been suggested that soldiers are primarily involved in a battle of the sexes, which they wage against their own siblings.

Andy Gardner, Ian Hardy, Peter Taylor, and Stuart West, in a theoretical study of how natural selection shapes the behavior of these larvae, published in the April issue of the American Naturalist, have rejected the brood-benefit hypothesis and found in favor of the view that their behavior is altogether spiteful.

Andy Gardner, now at St John's College, Oxford University, explains, "We found that the bizarre genetics of these wasps means that brothers value their sisters more than sisters value their brothers, and so if sterile larvae function for the good of the group then it should be brothers who more willingly make the sacrifice. Alternatively, if the sterile larvae are used by each sex to wage war against the other sex, then it should be primarily females who are interested in killing their brothers. As it happens, most sterile larvae are female, suggesting a primary role in sex conflict."

This work also explains the often strongly skewed sex ratios in these wasps, where female outnumber males, due to sex differences in killing behavior. More generally, it reveals how Darwinism can be used to explore the function of puzzling animal behaviors.

Source: University of Chicago

Explore further: Mosquito sex protein could provide key to controlling disease

Related Stories

Mosquito sex protein could provide key to controlling disease

December 13, 2017

If you thought the sex lives of humans were complicated, consider the case of the female Aedes aegypti mosquito, bringer of Zika, dengue, and yellow fever: She mates but once, in seconds and on the wing, with one lucky male; ...

New strategies against mosquitoes and other pests

August 1, 2016

South America is fighting a battle against tiger mosquitoes that transmit yellow fever, dengue fever and the Zika virus. In Central Europe, wine and fruit growers fear another year of massive crop failures due to a type of ...

Genes don't always dictate that 'boys will be boys'

November 9, 2017

As an evolutionary biologist focusing on animal behaviour, I'm sometimes asked what relevance our research has for human behaviour. Years ago, I would duck the question because it was such a passionately polarising, political ...

Recommended for you

AI and 5G in focus at top mobile fair

February 24, 2018

Phone makers will seek to entice new buyers with better cameras and bigger screens at the world's biggest mobile fair starting Monday in Spain after a year of flat smartphone sales.

Google Assistant adds more languages in global push

February 23, 2018

Google said Friday its digital assistant software would be available in more than 30 languages by the end of the years as it steps up its artificial intelligence efforts against Amazon and others.

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.