November 26th, 2016 by James Ayre
While farming has long been a known phenomenon amongst various ant species, there’s much that remains unknown. With that in mind, new research has revealed some interesting things about the symbiotic partnership and farming that goes on between the ant species Philidris nagasau and at least 6 types of plant within the genus Squamellaria on the Fiji archipelago, that are worth discussing here.
Amongst which, the symbiotic partnership between Philidris Nagasau and the various epiphyte plants in question has become so specialized that the basic life processes of the two are highly dependent — and, arguably, that the various species wouldn’t be able to survive without their symbiotic partner(s).
Also interesting, is that the farming partnership seems to have begun around 3 million years ago — going by the findings of an analysis based around the investigation of “the degrees of difference between homologous DNA sequences in both plants and ants as independent molecular clocks. Based on calibrated rates of mutation, one can work out approximately when the species involved in the interactions originated, and thus the earliest point at which the symbioses could have formed.”
These symbioses would have presumably begun after Squamellaria began adapting an epiphytic form — with the ants presumably making the approach more viable through their “aid” (mutualistic fertilization, and the planting of the Squamellaria in viable locations, amongst other things).
As some background — the plant genus Squamellaria is composed of epiphytic species that grow on tree trunks. Their seeds are collected by the ant farmers, who then plant them in viable fissures in the bark of host trees. They then germinate in these trees, and are actively managed and utilized.
“The plants colonize three or four tree species, which are also attractive for the ants, either because they produce readily accessible nectar, or because their bark is particularly soft, so that the ants can easily widen the cracks that form,” stated LMU botany professor Susanne Renner.
The press release provides more: “Squamellaria are adapted to this niche, as the hypocotyl of the germinating seedlings elongates into a unique ‘foot’, enabling the seedling to rapidly grow out of the bark crack and into the light. The seedlings then immediately form a tiny tuber with a preformed hole — the so-called domatium — into which ants enter to defecate and thereby fertilize the seedling. As the seedlings grow, the domatium becomes larger, forming a network of galleries connected to the outside, which the ants colonize to form large colonies, continuing to use some chambers for fecal matter, others just for their larvae. As epiphytes, Squamellaria species cannot draw on soil as a source of inorganic nutrients, and the ants promote their growth by supplying them with ‘fertilizer’. As the ants plant more seedlings, all of which they eventually colonize, they are creating a kind of village on the supporting tree, with many well protected nests.”
In this situation, the various plants don’t all host queens.
“One often finds dozens of colonies, connected by ant highways, on a single tree. All of these individuals are the progeny of a single queen, whose nest is located in the center of the system,” PhD student Guillaume Chomicki noted.
Certainly a different approach to agriculture, achieved very slowly over time, than the one of wide-scale deforestation, soil erosion and depletion, and desertification, being utilized now, and quite often in recent millennia.
The new research is detailed in a paper published in the journal Nature Plants.
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