Of Acacias and Ants


The bullthorn acacia and the ant Pseudomyrmex ferruginea provide us with a splendid example of co-evolution.  Co-evolution is essentially when a species adapts to the changes of another species, as this example will demonstrate.

Bullthorn Acacia

Basically, what happens is this.  The bullthorn acacia produces a unique protein source for the ants, and the ants live inside its thorns.  I said ‘unique’ because other acacias don’t have these protein structures, which by the way have no other known function — they’re just there to feed the ants.  So what’s the point of having protein structures for the benefit of other species?  That sounds a bit too generous, and it seems very inefficient energy-wise as well, in terms of evolution or survival of the fittest (just a quick note: fittest here doesn’t mean strongest; evolution by natural selection actually means the survival of the most adapted or adaptable species). 

But the bullthorn acacia is actually trading food and shelter for defence.  The ants in return protect the acacia (their food source and shelter), stinging everything that steps foot in their territory.  Moreover, they clean the grounds around the acacia killing other plants.  In short, the bullthorn acacia have mustered these ants to protect itself, at the cost of some energy, instead of evolving a defence mechanism of its own.

As should also be mentioned, other acacias have different defence mechanisms.  Many acacias produce poisonous chemicals to defend against herbivores.  The bullthorn acacia doesn’t need that, because they have the ants on their side.  The acacia protected by more ants is more likely survive.  This is co-evolution by natural selection.  It’s amazing, and whoa it makes me feel all warm and fuzzy!!!  But I still hate ants.  I was going to post a picture of the Pseudomyrmex ferruginea but I think I’ll link to it instead, because, god almighty, I hate ants.  And I guess I’ll have to steer clear of the bullthorn acacia from now on (not that I’ve ever been anywhere near one).

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