What is the functional significance of a keystone species?
A keystone species in an ecosystem plays a major role in the function of that ecosystem, and there are lots of examples that have been known. I would mention one that we’ve studied in Minnesota. I mean it may or may not seem like a keystone species, but deer turn out to be a keystone species. Deer eat a variety of plants, but they preferentially eat legumes, and by eating legumes they keep this kind of plant in low abundance, and that actually keeps the soil from becoming very fertile. When deer are in low densities, legumes become abundant, the soil becomes more fertile, and we’ve seen almost the doubling of soil fertility in a 20-year period in response to keeping deer out of areas compared to ones where they were present. So what are the identity factors for such a species? The most common interpretation of how to measure if something is identified as a keystone species would be to do an experiment in which you would add it or remove it from an ecosystem, and if you add or remove a
