Britannica Sources used in this answer

How do cacti and African euphorbias illustrate convergent evolution?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

A diagram showing the tentative evolutionary relationships among hominid species over the past four million years, with skull images and labeled species names connected by solid and dotted lines to indicate proposed evolutionary pathways. — phylogeny Tentative phylogenetic scheme for the evolution of the human lineage. Solid bars indicate the time ranges during which species are thought to have existed, based on fossil evidence. Dotted lines signify evolutionary relationships between hominin species that have been proposed on the basis of the fossil evidence.

Cacti and African euphorbias provide a classic example of convergent evolution, a process where unrelated or distantly related species independently evolve similar traits to adapt to comparable environmental pressures.123

While many cacti (family Cactaceae) and succulent euphorbias (family Euphorbiaceae) appear remarkably similar—often featuring thick, fleshy, water-storing stems and spines—they belong to entirely distinct plant families. Their shared physical characteristics, such as being succulent and adapted to arid desert conditions, are analogous rather than homologous; these traits evolved independently as efficient solutions for survival in water-scarce environments.453

Despite these superficial resemblances, the two groups remain biologically distinct. For instance, unlike cacti, many succulent euphorbias contain a milky, often poisonous latex sap. Furthermore, their reproductive structures differ significantly: euphorbias produce unique, cup-shaped clusters of reduced flowers called cyathia, which function as a single flower, whereas cacti possess their own specialized floral anatomy. Their convergence highlights how similar ecological demands can drive unrelated lineages toward similar evolutionary outcomes.5623