Convergent Evolution in Cacti and Succulents

Let’s begin with one observation that strikes anyone who travels widely. If you go to two distant areas that have similar climate and terrain, you find different types of life. Take deserts. Many desert plants are succulents: they show an adaptive combination of traits that include large fleshy stems to store water, spines to deter predators, and small or missing leaves to reduce water loss. But different deserts have different types of succulents. In North and South America, the succulents...