A guest post by Matt Christmas
You’d be hard pressed to find many people who hold ants in high regard. Whether that’s due to their destructive behaviour towards lawns, their ability to infest your house in no time at all, or the willingness of some ants to provide you with a nasty formic acid-filled bite after inadvertently stepping on their nests, ants do not inspire much human affection.
However, before we completely write ants off, we should give some consideration to the invaluable work they do for biodiversity. Ants play a key role in seed dispersal for around 11, 000 flowering plant species worldwide. They do not do this purely out of the goodness of their own hearts, however, and do require a reward in return for their hard work – a nutrient-rich appendage attached to the seed, known as an elaiosome, which they feed to their larvae.
The benefits to the plant come when the elaiosome has been removed and the seed is discarded amongst the fertile waste of the ant nest, which makes for perfect growing conditions. Mutualistic relationships between ants and their flowering plant counterparts appear to have evolved independently over 100 times, with the elaiosome being an excellent example of convergent evolution – different species evolving similar traits or characteristics independently of each other.
A recent study has shed light on the significance of this mutualistic relationship in terms of the diversification of flowering plants species (it is estimated there are around 300, 000 flowering plant species on Earth today). Seed dispersal distance 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. However, ants only transport seeds over very short distances (up to 200 m but usually only between 1-2 m). 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, it was found that flowering plant groups that were dispersed by ants 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 lot of impact when it comes to the diversification of flowering plants. And, with ants outnumbering us by around 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.