A keystone species reduces the likelihood of competitive exclusion which will in turn increase the number of species that could coexist in communities. Without the keystone species, competitive exclusion will increase and cause the dominance of certain species.
Is it possible for another species to take the role of keystone species by adapting or modifying its diet such that it will primarily consume the resulting dominant species?
Most definitions imply that if a species can be readily replaced, it should not be called 'keystone', but the truth is that this is rarely tested. For example, for most "keystone" seed dispersers, we do not know whether there are other dispersers are waiting to step in if the primary disperser is lost, although there is in some indication that there are.
Dear Patty,
This all lays in biocenotic interactions and in invasion processes that happen in every community and which intencity can grow with decreasing of amount of dominant species. Should note that is not obligatory that disappearance of dominant species will automatically rise or compensate it by existing sub-dominant. It is possible that type of community will be changed completely as such event is reliable with catastrophic natural phenomena as flood or fire...
I recomment to have a look on perfect book : Conceptual Ecology and Invasion Biology: Reciprocal Approaches to Nature (2006 - not in open access). If you need PDF, please, contact me over messanger.
Andrey
Excluding 'keystone species' can have extremely unexpected and irreversible effects that still seem to be poorly recognised. Many years ago I was asked "What's happened to the fish in Lake Manchar (Pakistan)? They suddenly disappeared in 1962." The reason was believed to be overfishing - in fact it was much more fundamental than that.
Cumulative human interventions in the flood discharge patterns in the Indus River Basin had changed the timing of over-bank spillages so that recruitment of the fry of the dominant but distant-spawning Major Carps into the Lake was eliminated. This disrupted the entire energetics of the ecosystem, and the energy flow between all species - even resident spawners in the Lake - was destroyed.
What followed was a classic example of an ecosytem bifurcation response, with the entire ecosystem energetics collapsing irreversibly to a much lower state. So simply eliminating one 'keystone' species (or in this case, a group of related and mutually interdependent species) did NOT allow another to take over. Instead a new and less complex and productive ecosystem emerged.
For a description of this event, see my old paper (attached) which I have placed on Researchgate in case anyone is interested.
That makes sense: if an entire guild of species is lost, the likelihood of species redundancy would be greatly reduced. Hypothesis: when a guild is composed of a single species, its loss would be more impactful.
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