Answer: Convergent evolution
Explanation:
The convergent evolution is a process by which the unrelated or not closely related organisms independently evolve with same traits as a result of being exposed to the same kind of environment or having the same ecological niches. These organisms are linked due to common ancestry.
The given situation is the example of convergent evolution, this is because of the fact that both species (Cacti and cactus-like euphorbs) are native plants of different countries. These species are not closely related but they are sharing common ancestral characteristic with Christmas poinsettia.
