What Effect Do Keystone Species Have On The Community

Certain species have a remarkably large impact in their communities. From the basic structure, balance, and the natural flow of the system, these species help determine the ecological functioning and are known as Keystone species. The impact they have on their communities is greater than would be expected based on their relative abundance and total biomass (Power et al., 1996, p.609). There are more than only one type of keystone species and they all influence their communities differently (Mills et al., 1993, P.220). The removal or extinction of a keystone species can alter the complete function of an ecosystem and can lead to the loss of other species. Throughout different ecological communities, simple to more complex systems, the Keystone

The rate which communities and ecosystems flow are controlled by the most abundant species, dominant species, who typically provide the major energy flow (Power et al., 1996, p.609). Dominant species may exert powerful control over the presence of other species which is caused by their competitive exclusion methods and at times predation (Krebs, 2006, p.414). But not all species have a competitive nature and predator tendencies which often leads to numerical superiority. Another concept was then developed to help describe species with lower abundance but a larger effect on their environment, the keystone species. The original criteria for a keystone species was to have a crucial presence in the maintenance, organization, and diversity of their community and to be exceptional compared to the rest of the community (Mills et al., 1993, p.219). This definition is quite broad leading to the importance of being able to identify keystone species to help maintain the integrity, and diversity of ecological communities. Libralato’s (2006)

A keystone predator can be defined as one of several other predators in a community that control the overall patterns of prey community structure (Menge et al., 1994, p.250). In short, the keystone predator is the dominant predator in a community. The intertidal sea star Pisaster ochraceus is perhaps the most famous keystone predator species. The sea star was experimentally removed from the zone where it lived and as a result, the population of mussel increased. This lead to a complete dominance of the mussels and reducing the overall diversity of barnacles and algae because the mussels crowded out other species (Mills et al. 1993, p.220) This sharp reduction in diversity and collapse of community structure commonly occurs when a keystone species is removed. It can be seen from the above example that predators can provide biotic resistance to invasions by consuming invasive species (Needles et al., 2015, p.1282). On the other hand, the opposite can occur and facilitate invasions if they decrease the native population that competes with other invaders. In Mills (1993) study, he stated that with the effective removal of a keystone predator from a system, an increase in one or several predators and decrease of several prey species will occur (p.220). It is, however, important to note the limitations of this prediction, many other factors can alter the results and must be taken into consideration when