Ecological dominance is the degree to which a species is more numerous than its competitors in an ecological community, or makes up more of the biomass. Most ecological communities are defined by their dominant species.
Examples
In heathland the dominant species are characteristically one or more species of heather or related plants.
On Earth, arguably, a large amount of its land ecosystems are dominated by human beings, making human beings the ecologically dominant species over much of the planet.