Why are Afro-Alpine plants on separate East African mountains similar?

The similarity of Afro-Alpine plants across the isolated peaks of East Africa is primarily due to historical climate shifts. Following the Pleistocene epoch, as temperatures increased, cold-loving plants were forced to retreat from lower elevations to the cooler, higher altitudes of the mountains. These mountain summits effectively acted as "islands" of cool climate, preserving these species while they became geographically separated from one another.12

While these populations are now isolated, they share a common ancestral history from when these cold-adapted plants occupied larger, more connected areas during cooler periods. Over time, these plants have undergone further evolution, leading to the development of related but distinct species on different peaks. Additionally, some of the striking physical similarities observed—such as the emergence of giant stem rosette plants—are examples of convergent evolution, where different species independently developed similar traits to survive the harsh, freezing conditions of high-altitude environments.123