In fact, natural selection might lead one to expect a ‘winner takes all’ competition. Each small space in an ecosystem would end up harbouring just one, amazingly well-adapted species.

However, many ecosystems are not like this. There are 300 different kinds of trees in a typical hectare of tropical forest. Even a habitat such as chalk grassland can support over 50 species per square metre. They do not seem to have adapted to different conditions but, according to Darwin, even plants are competing to survive. So how do these similar species co-exist?

The answer is that environmental differences can be subtle. Small variations in sunlight, in water, in the soil, or in how deep roots grow, can mean that similar plants experience different conditions. Also, the better the plants are suited to one precisely defined environment, the less likely they are to compete effectively with plants adapted to a slightly different one.

The renewed attention to variations in micro-environments features in the work of Professor Jonathan Silvertown of the UK-based Open University. He first showed how variations in water use help separate species in English country meadows. This established the importance of ‘hydrological niches’ – which differ based on how much effort it takes a plant to take up moisture from the soil, or to avoid getting waterlogged. He is now investigating some of the many thousands of species found in the Cape region of South Africa to record how his findings apply in other countries.