Workers hold key to power in nature's oldest societies

Nov 02, 2010
Three workers are with a queen (center) while a fourth worker looks on (center back). Credit: Richard Gill, University of Leicester

(PhysOrg.com) -- A new study analysing how complex, highly-evolved societies are organised in nature has found that it is workers that play a pivotal role in creating well-ordered societies where conflict is minimized.

For when it comes to determining who reproduces in ants, University of Leicester have found the humble worker is queenmaker – it is they who choose their queen.

This information is key to understanding the evolution of complex interdependent societies - over 100 millions years old - that have evolved mechanisms ensuring stable cohabitation and resolution.

What the Leicester team discovered surprised them: While Spanish worker ants were ruthless in determining who became their queen –and hence acquired the right to reproduce- the same species of ants in France, Germany and the UK are known to be more ‘apathetic’.

While Spanish workers bullied or even killed rival queens in order to choose their queen, UK workers are not aggressive at all and were loyal subjects to any number of queens.

The research by Dr Robert Hammond and Dr Richard Gill of the University of Leicester Department of Biology is published today in Proceedings of the Royal B.

The finding could have important applications. Dr Hammond said: “Some ants are pests, and in particular invasive ants - that have colonized new countries and continents - are very destructive causing many millions of pounds of damage. In a number of important cases ants have invaded because of a shift in their social organisation. So understanding the reason for differences in social organisation in a non invasive species is likely to help understand these problem species.”

The four-year study reveals that Spanish ant societies are composed of single family units where only one queen rules the roost –but UK ant societies are a more complex mixture of family units where lots of queens are having offspring

Spanish worker ants are truly revolutionary, the research found,while UK worker ants are more ‘apathetic’.

Dr Gill said: “Many animals – including humans - live in social groups and, as we all know, the interests of group members are often in conflict and ‘arguments’ often break out. Ants have some of the most integrated and complex societies found in nature and it is of great interest to understand if there are conflicts within their societies and how they are resolved. Because ants have been living in complex societies for many millions of years, and cooperation is highly important to their success, mechanisms that resolve such arguments should have evolved.”

“We sought to find out how the argument over who heads ant colonies is settled. This argument about who reproduces is not just confined to the ants we study, but is a general issue in socially living animals. In meerkats, only a few females reproduce, likewise in naked mole rats only a single ‘queen’ mole rat reproduces, yet in lions all females reproduce in a social group. The aim of this work is to help explain why we see such variation in who reproduces in socially living animals.”

The Leicester researchers studied the ‘twig ant’ - Leptothorax acervorum - that have more than one queen per nest (this is actually quite common in ants). However, in the Spanish population only one queen reproduces – even though other queens in the nest are capable.

“We found evidence that workers do indeed hold the power – and, like revolting peasants – the masses are ferocious with workers beating up – even killing - all but one queen who they preferentially groom and who ends up reproducing” Dr Hammond said.

But this ‘worker power’ is not found in all populations of twig ants. In fact in twig ant colonies from the UK, France and Germany and many other places – workers are not aggressive to queens at all and multiple queens end up reproducing. The colony in these cases is an assemblage of multiple families, rather than a single family as found in Spain.

Dr Hammond said: “Worker ants are known to be important players in various arguments that happen within the colony, but this is the first time worker ants have been shown to be so influential over which queens reproduce. Also, the contrast in worker power between the aggressive Spanish twig ant workers and the apathetic twig ant workers found in the UK and elsewhere is intriguing.

“The role of workers has been overlooked in the argument over who determines which queens reproduce. Also, a particular species is often thought to have fixed social organisation. This work shows that species can vary in fundamental aspects of how their societies are organised.”

While this study has established that in Spanish colonies of this ant it is worker behaviour that determines which queens reproduce researchers have yet to determine the ultimate reason why workers behave like this, and also why worker behaviour varies.

“We need to establish to what extent it is nature (genes) and nurture (environment) that is responsible for the difference in behaviour between Spanish and UK .”

Explore further: A step into the unmown creates a 'win-win' for wildlife and humans

Related Stories

Plotting and treachery in ant royal families

Feb 25, 2010

A team from the University of Copenhagen, led by postdoc Luke Holman of the Center for Social Evolution, describes in Proceedings of the Royal Society B, published on the 24 February 2010, that ant queens are much more d ...

Wood ant queen has no egg-laying monopoly

Jun 28, 2007

The reproductive monopoly of the ant queen is not as strong as is often thought. Dr. Heikki Helanterä and Prof. Lotta Sundström, biologists working at the University of Helsinki, Finland, investigated worker ovary development ...

How cheating ants give themselves away

Jan 08, 2009

In ant society, workers normally give up reproducing themselves to care for their queen's offspring, who are their brothers and sisters. When workers try to cheat and have their own kids in the queen's presence, their peers ...

Why do some queen bees eat their worker bee's eggs?

Dec 04, 2006

Worker bees, wasps, and ants are often considered neuter. But in many species they are females with ovaries, who although unable to mate, can lay unfertilized eggs which turn into males if reared. For some ...

The ant queen's chemical crown

Jun 30, 2010

The defining feature of social insects is that societies contain queens, which specialise in laying eggs, as well as workers, which are mostly infertile but take care of the offspring and the nest. However, when the queen ...

Recommended for you

Research helps steer mites from bees

3 hours ago

A Simon Fraser University chemistry professor has found a way to sway mites from their damaging effects on bees that care and feed the all-important queen bee.

Bird brains more precise than humans'

4 hours ago

(Phys.org) —Birds have been found to display superior judgement of their body width compared to humans, in research to help design autonomous aircraft navigation systems.

User comments : 0