Ants Farm Aphid Clones in Subterranean Rooms

Posted on July 5, 2012

Scientists have discovered that ants farm aphid clones in subterranean rooms. The researchers believe the farming method may help ants maximize honeydew yields. The yellow meadow ant, Lasius flavus, (pictured above) farms root aphids for sugar (honeydew) and nitrogen (protein). The scientists say these species of aphids have developed distinctive traits never found in free living species, such as the trophobiotic organ, which holds honey dew for the ants.

New research published here in BioMed Central's open access journal BMC Evolutionary Biology shows that over half of ant mounds contained only one of the three most common species of aphid, and two thirds of these has a single aphid clone. Even in mounds which contained more than one species of aphid, 95% of the aphid chambers contained individuals of a single clone. Researchers from the University of Copenhagen, University of Groningen and Rockefeller University used DNA microsatellite analysis to look at the genetic similarity of the three most common species of root aphids within L. flavus nests.

Aphid farming by ants is considered to be mutualistic. The ants cultivate and protect the aphids which in turn provide food for the ants. The scientists say that in farming mutualism, monocultures may reduce competition. They also say this may be the result of husbandry, caused by the ants selecting the very best aphids for their needs.

Results indicated that while there was considerable aphid diversity within the 7 kilometer test site at all sampling levels (ant mound, soil sample and chamber), monocultures occurred more frequently than expected. 52% of mounds and 99% of aphid chambers contained a single species and 60% of these contained a single clone. When multiple species or clones existed in the same mound they were kept separated.

Aniek Ivens, who led the research, says, "Although two years later most ant mounds seemed to contain the same clones, two mounds had gained new clones of their species. It is possible that either these aphids have been brought in or that they were previously at a very low level in the mound and missed during an earlier survey."

Ivens also says, "In a parallel with human farming methods this most likely gives colonies the possibility to actively manage the diversity and abundance of their livestock - allowing maximal honeydew yield from mature aphids that are kept under optimal conditions of phloem feeding and ant care. Ants also secure dietary protein by eating the excess of young aphids, and replacement of their honeydew-producing livestock when adult aphids become less productive."

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