A foundational species in ecology refers to a species that has a strong role in maintaining the structure of an ecosystem. These species can have significant effects on the environment and other organisms in their habitat. For instance, keystone species are often cited as foundational due to their critical role in regulating populations and supporting biodiversity. Their presence or absence can lead to profound changes in community dynamics. The health and stability of an ecosystem heavily rely on these foundational species, which foster various ecological interactions and processes.