Let's hear it for ants!
Thats right, ants. Without ants I would venture to stay that a lot of life as we know it would be radically different. One of the many ways in which ants fill important niche roles is as seed dispersers.
Known as myrmecochory, many species of plants rely on ants to move their seeds from place to place. They encourage the ants to do this by attaching appendages to their seeds called elaiosomes. Elaiosomes are little fleshy structures that are packed full of lipids and proteins. Foraging ants take these seeds back to their colonies where the elaiosome is eaten and the seed is then discarded. Ants have special chambers in their colonies for trash. They are basically little underground compost heaps.
When the seeds are thrown away, they suddenly find themselves in a very stable, nutrient rich area where they can safely germinate. It makes so much sense. The ants get a little meal and the plant has provided its offspring with one of the safest storage and planting environments. Next time you are hiking in the woods and see a population of plants that evolved this method, there is a good chance that an ant colony is near by.
There is also some evidence to suggest that the seeds gain a cleaning benefit from the ants as well. Living in close quarters and in such high numbers as ants do, disease is a particularly prevalent issue. Because of that, ants have evolved specialized glands that secrete a liquid with antimicrobial properties. It is possible that ants may inadvertently clean seeds that enter their nest with this fluid. Since diseases, especially certain types of fungi, are one of the leading causes of seedling mortality, it is very possible that this is yet another added benefit of having ants as your seed dispersal agent. More research is necessary to see if this is truly what is going on.
The sheer number of plants species that utilize ants in this way is staggering. Here in North America, the majority of myrmecochorous plants are spring ephemerals. There is a lot less food available to ants in the spring, making these seeds very appealing. Once summer hits, scavenging ants are less likely to pay attention to seeds in lieu of more nutritious food available. Here are just a few examples you may be familiar with:
Photo Credit: Cotinis