Dispersal of eggs over short distances may happen under many circumstances, for example by overflow from pools. However, long-range dispersal is comparatively rare and usually happens only in shallow pools without much vegetation. When dispersal takes place over longer distances, the vectors commonly would be favourable wind or the feet of birds, both of which are episodic and unreliable vehicles. Such constraints on dispersal provide a plausible reason for the high proportion of endemic species throughout the region; in the Drakensberg alone there are four. It also could explain the morphological variability of some widespread species, for example Branchipodopsis wolfi in Botswana.