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Fig. 4 | BMC Ecology and Evolution

Fig. 4

From: Revisiting Theron’s hypothesis on the origin of fairy circles after four decades: Euphorbias are not the cause

Fig. 4

Examples of significant size differences between dead Euphorbia damarana and fairy circles. In the Giribes, none of the largest found dead E. damarana reached nearly the size of the large mega circles, which had a mean diameter of 16 m (a). Likewise, none of the smallest found dead E. damarana at Brandberg reached the size of small FCs with diameters between 2 and 3 m (a). In the box plots, the mean and median are indicated by the red and black horizontal lines, respectively. Euphorbia damarana plants only die when they have large sizes, hence small vital shrubs are irrelevant for the causal relationship as proposed by the Euphorbia hypothesis. The examples from the plot Gir- 2 in (b) and (c) show dead shrubs with an extent of 9.8 m and 7.9 m, respectively, while vital green shrubs growing next to them can be much smaller with diameters of only 1–2 m. Drone image from 2020 of a large mega circle in plot Gir-1, stretching over 16 m in extent, while the dead E. damarana next to it measures only 5.5 m (d). The sizes of the FC and shrub are stable, as the Google satellite image from 2009 shows (e). Drone image of a very small FC (arrow) in plot Bra-1 with a diameter of only 2.6 m, while the dead E. damarana in the lower right of the image has a typical diameter of 7.1 m (f). The small FC was already there in 2010, as the Google satellite image shows (g). Such small FCs cannot be caused by the typically large dead Euphorbias

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