In ecology class, students are taught the effects of keystone species, the dominant species in the ecosystem. They are the top dogs, the big fish. The keystone species have a disproportionate effect on their environment and can determine the types and numbers of species in their ecosystem, not just their prey. A recent study published in the journal Frontiers in Ecology and the Environment shows that this keystone species effect is similar for both terrestrial and ocean-based predators.