Which ecological process is shown by the diagram?

Insolation refers to the amount of solar radiation reaching a given area. It plays a significant role in climate and hence affects the types of organisms that can inhabit an area. However, insolation itself is not an ecological process but a climatic condition influencing the environment.

Dispersal is the movement of organisms from their birth site to their breeding site ('natal dispersal'), as well as the movement from one breeding site to another ('breeding dispersal'). While it can influence the dynamics of how species are distributed within an ecosystem, it does not explain the transition of species within a community over time as shown in the diagram.

Advection is a physical process where heat or matter is transported horizontally in the atmosphere or the ocean due to the movement of currents. Advection can influence the distribution of organisms, but it does not represent the sequential change in species structure over time, as depicted in the diagram.