Largest on earth: Discovery of a new type of fairy circle in Angola supports a termite origin

1. Circular bare patches occur in high numbers among the vegetation of the Namib Desert margin. There is an ongoing scientific debate on the origin of these so-called fairy circles (FCs). One of the most frequently discussed hypotheses regards the bare patches to be the result of localised herbivory by sand termites of the genus Psammotermes (family Rhinotermitidae). 2. In all earlier publications, the fairy circles of the Namib Desert region within their entire range from Angola through Namibia to South Africa were, in principle, regarded to be of one type, albeit increasing in size towards the north. Here we present evidence that at -16.23 degrees latitude there is an abrupt discontinuity which separates the FCs on either side from each other. 3. South of this discontinuity all studied FCs share the properties of the previously described fairy circles in Namibia and South Africa, especially the presence of Psammotermes termites. 4. In contrast, north of -16.23 degrees S the FCs are much larger and are caused by a different and undescribed termite species, most closely related to the harvester termite genus Microhodotermes (family Hodotermitidae). The two sets of fairy circles differ in a specific set of morphological features, associated termites, and soil parameters. 5. The observed juxtaposition of the newly discovered large structures caused by a hodotermitid termite and the Psammotermes FCs caused by a rhinotermitid species is interpreted as an interesting example of convergent evolution resulting in similar ecological structures.

Automated summary

In the Namib Desert margin, circular bare patches known as fairy circles are a subject of ongoing scientific debate. Previous studies regarded fairy circles in the region as one type, albeit increasing in size towards the north, but recent evidence shows a distinct discontinuity at -16.23 degrees latitude. South of this line, fairy circles share characteristics of previously described circles from Namibia and South Africa, while north of the line, there are larger fairy circles caused by a different termite species closely related to the harvester termite genus Microhodotermes. This juxtaposition is seen as an example of convergent evolution resulting in similar ecological structures.