Adaptive Traits in Diverging Lizard Populations

In a recent study on speciation in a population of lizards found in a tropical rainforest, researchers discovered that a subset of the population had adapted to live on the trees while another subset remained on the ground. The arboreal lizards developed elongated limbs and specialized toe pads, enabling them to navigate the complex three-dimensional habitat. In contrast, the terrestrial lizards exhibited adaptations such as broader bodies for stability on the ground. This divergence provides a clear example of adaptive radiation and niche differentiation.

Given this scenario, which of the following concepts best explains the emergence of these divergent traits in the lizard populations?