A new thought about termites (Rhinotermitidae) on two continents
(writing in progress)
Here is some new lateral thinking at the family level, and at the level of ecological engineering, on the topic of Rhinotermitidae.
Both Coptotermes (which is best-known in Australia but extends even to Africa) and Psammotermes (which occurs in Africa and Asia, in arid areas) belong to the Rhinotermitidae, a family most familiar to most naturalists in its North American form (Reticulitermes).
The North American genus is really the only important timber pest in the USA, and even reaches Canada (southern Ontario). It has thrived at surprisingly high latitudes for a termite, partly because of central heating.
However, Reticulitermes is a non-event in the sense of ecological engineering: it does not even possess a nest, living simply as a diffuse collection of individuals that breed anywhere within their tunnel system in wood. There is a colony, but it has no centralisation.
Now, Coptotermes is responsible for that wonder of Nature, the hollow tree that continues to thrive with its heartwood eaten out up into the branches (epitomised by certain tropical Australian eucalypts).
This has all sorts of implications for nutrient recycling, fire-proneness, etc. A symbol of the effects of Coptotermes is the didjeridu.
For its part, Psammotermes (assuming that it really is responsible for the grass circles) has its own ‘hollowing out’ pattern.
Whereas Coptotermes produces hollowness easily visualised as a tube (a hollow trunk of branch), Psammotermes seems to produce hollowness easily visualised as a ring/circle.
In both cases, the termites have eaten away plant matter in a central space, producing emptiness and thus managing their microenvironment.
Both Coptotermes and Psammotermes are dominant termites in their respective ecosystems: eucalypt woodlands and semi-desert dunes (on different continents despite the fact that the two genera overlap at a gross scale in geographical range).
The effects of Coptotermes at a landscape scale: a hollow-treed woodland, a woodland of hollow trees.
Inasmuch as this promotes the health of these eucalypts, and inasmuch as these eucalypts have deep roots that retrieve nutrients from groundwater (as well as milking the atmosphere for aerosols), there is a powerful effect on the ecosystem, abetted by the termites. It is hard to say how much difference the hollowing makes to the trees.
However, I assume that the trees actually benefit from this hollowing, as opposed to merely tolerating it – at least at the level of populations/species (I’m not necessarily invoking a benefit within the life of an individual tree, so I’m likely to lose most narrow-minded neodarwinists in this rationale).
Please note that the main engineering effects of Coptotermes have to do with space and time in the vertical dimension. Coptotermes engineers how resources flow, by creating tubes/conduits/passageways for air and indirectly facilitating the flow of other resources including water and nutrients, partly via fire.
The effects of Psammotermes at a landscape scale are hard to know at this stage. However, if it is true that Psammotermes digs down to the groundwater even at the edge of the Namib, perhaps something analogous to Coptotermes? Based on the power of retrieval of water from deep in the ground, I speculate that Psammotermes can operate powerfully at the surface, engineering aspects of the semi-desert vegetation.
The most obvious manifestation of this may be the grass circles so conspicuous from the air in parts of the pro-Namib? Could it be that, in their own way, these represent cross-sections of a system of ‘tubes’ whereby Psammotermes forges a deep connection in vertical space?
I speculate that by virtue of access to groundwater, Psammotermes has the metabolic power to engineer the water supply also near the surface: cutting back Stipagrostis to preserve patches of bare ground in which the subsoil water is conserved instead of transpired?
(writing in progress)
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