What triggers adaptive radiation?

Adaptive radiation is triggered by environmental changes such as the emergence of new habitats or significant shifts in climate. These changes create new ecological niches, allowing species to evolve and diversify rapidly. When a population encounters a novel environment, it may adapt to utilize different resources or occupy different ecological roles, leading to the formation of new species that are better suited to the various conditions present in that environment.

For instance, when a species evolves to exploit a newly available habitat (like an island after landmass separation), it can lead to a variety of forms adapted to various niches in that ecosystem, demonstrating the concept of adaptive radiation. This process highlights the dynamic relationship between species and their environments, emphasizing how external factors can influence evolutionary pathways.

In contrast, stable environmental conditions typically do not stimulate significant evolutionary change as species are already well-adapted to their environment and there is limited selection pressure to drive diversification. Increased genetic similarity among populations might suggest a lack of differentiation rather than an increase in species diversity, and inhibition of speciation processes would certainly lead to less divergence rather than more.