Spiteful soldiers and sex ratio conflict among parasitoid wasps

Apr 03, 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: New alfalfa variety resists ravenous local pest

add to favorites email to friend print save as pdf

Related Stories

Mosquitoes can't spot a spermless mate

Aug 08, 2011

A female mosquito cannot tell if the male that she has mated with is fertile or 'spermless' and unable to fertilise her eggs, according to a new study from scientists at Imperial College London.

Recommended for you

New alfalfa variety resists ravenous local pest

21 minutes ago

(Phys.org) —Cornell plant breeders have released a new alfalfa variety with some resistance against the alfalfa snout beetle, which has ravaged alfalfa fields in nine northern New York counties and across ...

In the 'slime jungle' height matters

32 minutes ago

(Phys.org) —In communities of microbes, akin to 'slime jungles', cells evolve not just to grow faster than their rivals but also to push themselves to the surface of colonies where they gain the best access ...

Former Iron Curtain still barrier for deer

3 hours ago

The Iron Curtain was traced by an electrified barbed-wire fence that isolated the communist world from the West. It was an impenetrable Cold War barrier—and for some inhabitants of the Czech Republic it ...

Humpback protections downgrade clears way for pipeline

13 hours ago

Environmentalist activists on Tuesday decried Canada's downgrading of humpback whale protections, suggesting the decision was fast-tracked to clear a major hurdle to constructing a pipeline to the Pacific ...

User comments : 0

More news stories

In the 'slime jungle' height matters

(Phys.org) —In communities of microbes, akin to 'slime jungles', cells evolve not just to grow faster than their rivals but also to push themselves to the surface of colonies where they gain the best access ...

New alfalfa variety resists ravenous local pest

(Phys.org) —Cornell plant breeders have released a new alfalfa variety with some resistance against the alfalfa snout beetle, which has ravaged alfalfa fields in nine northern New York counties and across ...

Former Iron Curtain still barrier for deer

The Iron Curtain was traced by an electrified barbed-wire fence that isolated the communist world from the West. It was an impenetrable Cold War barrier—and for some inhabitants of the Czech Republic it ...

Rainbow trout genome sequenced

Using fish bred at Washington State University, an international team of researchers has mapped the genetic profile of the rainbow trout, a versatile salmonid whose relatively recent genetic history opens ...

Robot scouts rooms people can't enter

(Phys.org) —Firefighters, police officers and military personnel are often required to enter rooms with little information about what dangers might lie behind the door. A group of engineering students at ...