Cannibalism helps fire ants invade new territory



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Fire ant stings can be deadly to people who have an allergic reaction to their venom.
Forest and Kim Starr/Flickr, CC BY-SA

Pauline Lenancker, James Cook University and Lori Lach, James Cook University

Tropical fire ants (Solenopsis geminata), originally from central and South America, are a highly aggressive, invasive ecological pest. Our new research has shed light on how they successfully establish new colonies.

An allergic reaction to painful tropical fire ant bites.
Pauline Lenancker, Author provided

While we don’t know exactly how widespread tropical fire ants are in Australia, they are well established around Darwin and Katherine, as well as on Christmas Island and Ashmore Reef. Disturbing one of their nests will result in many workers inflicting painful stings on the intruder, and can trigger an allergic reaction in some people.

When invasive ants move to a new region, the pioneers may be one or a few colonies. Because these pioneers are isolated, they often inbreed, which causes genetic problems in their offspring. But our new research, published in Scientific Reports, reveals how tropical fire ants use cannibalism to survive and spread, despite their low genetic diversity.




Read more:
Eradicating fire ants is still possible, but we have to choose now


Sons and daughters

Founding new colonies is how fire ants spread. Queens fly off to start their own colonies just after they have mated. It is a perilous journey – they need to avoid predators and find a good spot to start laying eggs. If queens do not quickly rear daughters that can forage, called workers, they will starve to death.

Queens can lay two different types of eggs: fertilised eggs, which will develop into workers, and unfertilised eggs, which will develop into males. Therefore, female workers have two copies of each gene (diploid), while males have a single copy of each gene (haploid). However, when an ant queen and her mate are closely related, a flaw in the sex determination system of ants causes half of the fertilised eggs to develop into diploid males instead of workers.

The role of males is only to mate with queens – they do not forage, and they die after they have mated. Queens founding a colony have no interest in producing males, because males will not feed them. What’s more, diploid males are often sterile, and their larvae are larger than worker larvae. Therefore, queens can waste precious resources feeding fat useless sons instead of workers.

We wanted to find out how common diploid males are in field colonies, and how queens could successfully start colonies despite them. Understanding how tropical fire ants spread, we hope, can help us stop them expanding their range.

Abandoned and eaten

Our field sampling of tropical fire ant colonies around Darwin revealed eight out of ten colonies produced diploid males.

We collected 1,187 queens that had just mated, and assigned them to start colonies on their own or with other queens.

We observed that in 34% of colonies producing diploid males, diploid male larvae were placed in the colony trash pile by the queens instead of being kept with the worker larvae. It is usual for ants to keep dead individuals away from the rest of the colony, but when we looked at some of these abandoned larvae under a microscope, we realised they were still alive.




Read more:
Curious Kids: do ants have blood?


Queens not only abandoned their sterile sons, they ate them. Three-quarters of the 109 sterile male larvae disappeared from the colonies within 12 days of when we first observed them. Because the queens were the only adult ants present in the colony, this means the queens were eating their diploid males or feeding them to their worker larvae.

This cannibalistic behaviour allowed the queens to redirect nutrients towards themselves or productive members of their colony. Diploid male larvae require more food than worker larvae to develop, so we expected queens from diploid male producing colonies to lose more weight than queens from colonies that only produced workers, but we found that was not the case. Queens with diploid males lost less weight or as much weight as queens from regular colonies, probably because they ate their sterile sons.

We also found queens who worked together in groups to start a colony reared more workers. Therefore, queens in groups would likely have a better chance of survival even if they produced sterile males. But in 6% of colonies, queens did not tolerate having housemates and dismembered other queens.

A queen dismembered by a tetchy rival.
Pauline Lenancker, Author provided

For tropical fire ants, cannibalising sterile sons and cooperative brood rearing among queens are two behavioural mechanisms for avoiding inbreeding costs. A third possible mechanism for the queens is to “sleep around”.

Promiscuity would increase the chance of mating with a genetically different male, and reduce the likelihood of producing diploid sons.

Queens only mate right before starting their colony and store the sperm in an organ called the spermatheca. We genetically analysed sperm from the spermatheca of 40 queens, but found no evidence queens had mated with more than one male.

Tropical fire ants are currently established on Ashmore Reef, a protected Australian Marine Park which is an important breeding site for seabirds and turtles. The invasive ant threatens this sanctuary by attacking seabird and turtle hatchlings. Accidental spreading of tropical fire ants to suitable habitats in the Northern Territory, Queensland and Western Australia would threaten invaluable ecosystems as well as our health and lifestyles.




Read more:
How we wiped out the invasive African big-headed ant from Lord Howe Island


The current eradication program for the closely related red imported fire ant (Solenopsis invicta) in Queensland has been granted A$411 million over ten years, and failure to eradicate red imported fire ants could cost Australia A$1.65 billion per year in damaged crops, livestock harmed and people treated. The more we learn about invasive ant biology, the closer we are to new methods of preventing their spread.The Conversation

Pauline Lenancker, PhD student in biology and ecology, James Cook University and Lori Lach, Associate Professor, James Cook University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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Article: How to Buy the Right Bushwalking Boot


Bushwalkers/hikers/trekkers (call it what you will) know that the right boot for an individual walker is absolutely essential out in the wild (or as we might call it Australia, out in the bush or out in the sticks). Many a bushwalk has been ruined or seriously curtailed by having the wrong boot. For me, when I’m doing some serious walking and covering large swathes of territory, blisters become a major problem.

The link below is to an article that provides some tips on what to look for when buying a bushwalking boot.

For more visit:
http://www.australiangeographic.com.au/outdoor/guide-to-buying-the-perfect-hiking-boot.htm.

Peru: Uncontacted Amazon Tribe Under Threat


The Peruvian government is planning to abolish a reserve that protects the territory of an as yet uncontacted Amazon tribe in Peru. Thankfully the tribes territory extends into Brazil and this section of their territory appears safe for the time being.

For more visit:
http://news.mongabay.com/2011/0601-survival_murunahua.html

 

NSW Road Trip 2010: A Few Thoughts From the Road


It is now day 5 of the road trip and I have already covered almost 3000km. As you can appreciate covering that amount of territory in 5 days doesn’t leave a lot of time to Blog, especially when I have been trying to keep the website updated as well.

See the NSW Road Trip 2010 website at:

http://www.kevinswilderness.com/NSW/nswRoadTrip2010.html

What I thought I might do in this Blog is just pass on a few thoughts that have come to me while I have been driving around this great state of Australia – New South Wales. Let’s call this post, ‘A Few Thoughts From the Road.’

I have often thought that the governments of this country are wasting a great opportunity in promoting tourism in Australia. With such great distances to travel in Australia, wouldn’t it be great if the governments came up with an action plan to improve the rest areas throughout the country. Certainly some of them have been upgraded to a wonderful state – but then there is a lack of maintenance.

Many of the rest areas I have stopped at in the last few days have no facilities at all. Often they are nothing more than an overloaded garbage bin on the side of a road, with limited space in which to park.

To cut a long story short, I think Australia’s tourism industry would get a great shot in the arm if rest areas were improved across the country. It would also be good if hey could be located somewhere with a good view, an attraction, a small park for families, etc.

To go a step further (and this is perhaps pie in the sky), wouldn’t it also be great for the many Australians that drive throughout the country on camping/caravan holidays, if a percentage of these rest areas had some limited facilities for tents and caravans as well?

Perhaps a lot more people would travel around the country if such improved rest areas were created. There would also need to be some plan to keep the maintenance of these areas up to scratch also.

Another thing that militates against the travelling tourism that is fairly popular in Australia (it could be far greater), is the condition of many of the caravan parks across the country. To be sure, there are some excellent parks – but there are also a large number of parks that charge top dollar for run down facilities and grubby grounds. These poor operators need to lift their games to provide good facilities for their customers or they won’t get the return business that caravan parks depend upon. They need to spend a bit of money in order to make money.

I won’t return to a caravan park in which I had a bad experience – whether it be top dollar for run down facilities, poor service, poor attitudes of operators, etc. Some of these places just have no idea how to run a successful caravan park.

More thoughts to come – these will do for today.