In the Knersvlakte, a closer look at the stony ground reveals that the quartzfields are actually carpeted with living stones: small succulent plants, belonging to the genus Argyroderma. Part of the South African Succulent Karoo, the Knersvlakte is a semi-desert region known for having by far the highest diversity of succulent plants on Earth.
While tall trees are easily noticeable, most plant species are actually small. Boucher and colleagues proposed the idea that small plants split into different offspring species (a process known as ‘speciation’) faster than large plants, thereby explaining why most species of plants on Earth are small.
According to Boucher and colleagues, faster rates of speciation in small plants largely come down to how they perceive the environment around them. To a small plant, two patches of soil a few metres apart might seem like totally different environments, and moving to the next valley might seem like crossing a whole continent.
The species on the cover, Argyroderma fissum, is part of a large group called the Ruschioids (Aizoaceae family), which diversified at one of the fastest rates known in plants worldwide. The genus Argyroderma, to which the species belongs, is even more impressive: it is made up of 11 different species, all of which are endemic to quartz patches of the Knersvlakte, a tiny region a mere 100×80 km across.
Read the Viewpoint by Boucher and colleagues:
Boucher, F. C., Verboom, G. A., Musker, S. and Ellis, A. G. (2017) Plant size: a key determinant of diversification? New Phytologist 216: 24–31. doi: 10.1111/nph.14697