The species according to their role are divided as:
• Dominant species
These are species with substantially higher abundance or biomass than other species in a community. They exert a powerful control over the occurrence and distribution of other species. For example: Tidal swamps in the tropics are usually dominated by species of mangrove (Rhizophoraceae).
• Keystone species
These are species that is not necessarily abundant in a community yet exerts strong control on community structure by the nature of its ecological role or niche. A small number of keystone species can have a huge impact on the environment.
A keystone species’ disappearance would start a domino effect. Other species in the habitat would also disappear and become extinct. The keystone species’ disappearance could affect other species that rely on it for survival. For example, the population of deer or rabbits would explode without the presence of a predator. The ecosystem cannot support an unlimited number of animals, and the deer soon compete with each other for food and water resources. Their population usually declines without a predator such as a mountain lion.
• Foundation Species
Foundation species play a major role in creating or maintaining a habitat that supports other species. Corals are one example of a foundation species in many islands in the South Pacific Ocean.
Corals produce the reef structures on which countless other organisms, including human beings, live. Umbrella Species An umbrella species is a large animal or other organism on which many other species depend.
• Umbrella species
Umbrella species are very similar to keystone species, but umbrella species are usually migratory and need a large habitat.
Protection of umbrella species is thought to automatically protect a host of other species. Tigers are an example of an umbrella species. Efforts to save wild tigers in forests in the Indian state of Rajasthan also accomplish the goal of saving other species there, such as leopards, boars, hares, antelopes, and monkeys.
• Critical Link Species
They are species that play an important role in supporting network species as pollinators, dispersal agents, absorption or circulation of nutrients, etc. Mycorrhizal fungi help the vascular plants in obtaining inorganic nutrients from soil and organic residues.
• Flagship species
Flagship species are species that have the ability to capture the imagination of the public and induce people to support conservation action and/or to donate funds.
These are popular, charismatic species that serve as symbols and rallying points to stimulate conservation awareness and action.
Examples of flagship species include the Bengal tiger, the giant panda, Asian elephant (Elephas maximus), etc.
Flagship species can represent an environmental feature (e.g. a species or ecosystem), cause (e.g. climate change or ocean acidification), organization (e.g. NGO or government department) or geographic region (e.g. state or protected area).
• Indicator species
An indicator species is an organism whose presence, absence or abundance reflects a specific environmental condition.
Indicator species can signal a change in the biological condition of a particular ecosystem, and thus may be used as a proxy to diagnose the health of an ecosystem. For example, plants or lichens sensitive to heavy metals or acids in precipitation may be indicators of air pollution.
Indicator species can also reflect a unique set of environmental qualities or characteristics found in a specific place, such as a unique microclimate.
• Edge species
The species which are found abundantly in ecotone boundary are known as edge species.