Keystone species is a species, which has a significant and disproportionately large influence on the community structure and characteristics. It has often considerably low abundance and biomass, as compared to dominant species. Removal or decrease in number of keystone species, causes serious disruption in structure and function of community. In intertidal region, starfish feeds on mussels. Removal of starfish leads to dominance of mussel population, that excludes algae and browsing species.