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In defence of the humble ant, champion of biodiversity

You’d be hard pressed to find many people who hold ants in high regard. That might be due to their destructive behaviour towards lawns, their ability to infest your house in no time at all, or a willingness…

Ants might be a pain … but they play a vital role in maintaining the variety of plant life we see around us. mraandrews

You’d be hard pressed to find many people who hold ants in high regard. That might be due to their destructive behaviour towards lawns, their ability to infest your house in no time at all, or a willingness to provide you with a nasty formic-acid-filled bite if you inadvertently step on their nest.

But before we write off ants completely, we should give some consideration to the invaluable work they do for biodiversity.

Several studies in recent years – including this one, this one and, most importantly, this one from 2009 – show ants play a key role in seed dispersal for around 11,000 flowering plant species worldwide.

The ants don’t do this hard work purely out of the goodness of their hearts – they do it for a reward. That reward is a nutrient-rich appendage attached to the seed, known as an elaiosome (see image below), which the ants feed to their larvae.

The benefits to the plant come when the elaiosome has been removed and the seed is discarded among the fertile waste around the ant nest, which provides perfect growing conditions.

Mutualistic relationships between ants and their flowering plant counterparts appear to have evolved independently more than 100 times, with the elaiosome being an excellent example of convergent evolution – that is, different species evolving similar traits or characteristics independently of each other.

Bloodroot seeds with elaiosomes (the gelatinous, white-speckled part) still attached. cotinis

The 2009 study mentioned above – by biologist Szabolcs Lengyel and colleagues – shed light on the significance of this mutualistic relationship in terms of the diversification of flowering plant species (it is estimated there are roughly 300,000 flowering plant species on Earth today).

Seed dispersal is vital to the connectivity of plant populations – the greater the distance a seed can be dispersed, the greater the level of connectedness between populations. But ants only transport seeds over very short distances – up to 200m but usually only over 1-2m.

Therefore, any plant relying on ants to disperse its seed will be limited in its ability to spread out over large distances. This limited dispersal distance will lead to geographically isolated populations – the perfect conditions for diversification and speciation.

Indeed, the 2009 study found that flowering plant groups that were ant-dispersed contained more than twice the number of species than closely related species that did not rely on ants for seed dispersal. By dispersing seeds only over short distances, ants have directly assisted in increasing the global diversity of plants.

So, ants have a significant impact when it comes to the diversification of flowering plants. And, with ants outnumbering humans by roughly 1.4 million to one, we shouldn’t be too hasty in writing them off as a pest.

Without ants, the world would lack a lot of the floral beauty we see around us today.

Join the conversation

9 Comments sorted by

  1. Tim Scanlon

    Debunker

    My wife did her honours thesis on weed seed dispersal by ants. They are fantastic little critters, even if they are annoying at times.

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  2. Neville Mattick

    Grazier: ALP Member at A 4th Generation Grazing Station

    Amazing discussion piece!

    I love Ants, my Farm does, it is covered in them fence to fence - make that tens of square kilometres, not a suburban block (same applies though by scale).

    Meat Ants are probably my favourite, there is a huge nest just outside my office and twenty in the Ha around that, they are as tough as anything is.

    The do invaluable work for us - love your Ant.

    Incredible to read the significance of them for Biodiversity.

    In fact I have found in Box Gum Grassy Woodland…

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  3. Trish Donovan

    logged in via Twitter

    Hi,

    I have learnt to love the ant. These foragers are nature's cleaners, I let them get on with their work. But, I do have murderous thoughts towards flies (not dragonflies) even though they have their uses.

    Trish.

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  4. Phil Dolan

    Viticulturist

    Seed dispersal. Very important. I remember doing an assignment on the number of ways it happens. It struck me that when insects or animals are in the equation, it's the plant that is calling the shots. Plants developed a strategy and the agents just followed. So are plants more clever than insects or animals? No. I don't think there was a plant committee that worked it out, but it is fascinating.

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  5. Dianna Arthur
    Dianna Arthur is a Friend of The Conversation.

    Environmentalist

    I always feel guilty when, erm, 'discouraging' an ant raid in my kitchen as ants are just being ants.

    Have suffered revenge by bull-ant: recommendation when brush cutting; tuck jeans into boots if near bull-ant nest, one little beast crawled up my leg and bit my inner thigh. My shrieks and hasty undressing in the garden brought a couple of neighbours running thinking I was having some kind of fit. Took weeks before bite healed, however have good relationship with neighbours.

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    1. Alison Jobling

      logged in via Facebook

      In reply to Dianna Arthur

      Dianna, if you want to 'discourage' ants from your kitchen without killing them, I'd suggest sprinkling talcum powder across their incoming path. The talc means that they can't smell the trail, so are unable to keep coming into the kitchen. It may take a couple of tries on various trails, but I've found it works wonderfully, and saves my conscience at the same time.

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    2. Tim Scanlon

      Debunker

      In reply to Alison Jobling

      I can second that one. Talc or any other fine and fragrant powder does the job.

      Dianna, I always found that the bullants were very fast climbers, so the jean tuck only worked if you were passing through quickly. When we were fencing we'd often use a distraction of some sort, usually some food.

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  6. Kevin Gilman

    logged in via Twitter

    My collection of dwarf cyclamen naturalised in grass is spreading far faster than the cyclamen's own intriguing "drilling rig" seed implanting mechanism could account for. I conclude ants must be responsible. So I say go ahead guys, but please go steady with the aphid farming, that's not so helpful!

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  7. Jon Murray

    logged in via email @iinet.net.au

    I like ants. Won't hear a word against them.

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