Why Did Some Termite Species Come To Depend On Fungus For Wood-Digestion?
In the United States termites are mostly concerned with infesting houses and consuming cellulose from wood, but in other countries termites are also farmers. More specifically, several exotic termite species are fungus farmers. Termites have been farming fungi for millions of years. In fact, just recently researchers unearthed a twenty five million year old fungus farm located within the Mountains of Tanzania. According to the researchers who discovered the ancient fungus farm, the fungi were ordered in complex rows, and termites used to feed the fungi tiny pellets of plant matter in order to facilitate their growth. This particular fossilized fungus farm is the oldest example of farming on the earth. So why are fungi so important to termites? And why did termites acquire the need to farm fungi?
Many scientists are amazed that termites are able to digest woody forms of plant matter. Very few animal species consume wood since wood is obviously hard and not very nutritious. You may be surprised to learn that there are several species of termite that exist today that never learned to digest wood on their own. These termites require fungi in order to break-down and convert woody plant matter into digestible eating-material. Fungus-farming termites will gather woody plant matter in order to feed their fungus crops. Termites will chew the hard plant matter until it forms a small pellet. Termites then feed these small pellets to the fungi. The fungi will eventually sprout mushrooms that the termites will eat. When termites consume these mushrooms, they are also consuming converted cellulose that came from the plant matter pellets.
Since termites have been cultivating fungi for millions of years, certain termite and fungus species have developed symbiotic relationships. As termites and fungi have evolved together, both have adapted to benefit one another. Today, Africa is home to the greatest degree of diversity among fungus-farming termite species. Therefore, fungus-farming termites probably originated somewhere on the continent. Genome sequencing of both termites and their fungus symbionts has also supported the “african origin” theory. DNA studies have revealed that two fungus-termite species migrated to Asia on two separate occasions.
Today scientists are still not certain as to how termites and fungi evolved to become symbionts. One theory states that ancient termites consumed fungi that grew out of the termite feces that had lined nest walls. Obviously, termite feces is largely composed of wood and other forms of plant matter. The fungi that grew out of the termite feces broke this wood and plant matter down, making it digestable for termites. Termites may have treated the emerging fungi as an extra food source. This behavior was repeated until, at some point, termites and fungi formed a symbiotic relationship. This theory seems reasonable given the fact that non-farming termites seem innately attracted to fungi as a food source.
Have you ever heard of any other type of insect that shares a symbiotic relationship with fungi?
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