1. Endemic species
Endemism is the ecological state of a species being unique to a defined geographic location, such as an island, nation, country or other defined zone, or habitat type; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. they are only found in certain locations, they require special conservation efforts
Animal examples: Lemurs of Madagascar, tortoises of the Galapagos, polar bears, koalas, kangaroos.
Plant examples: Redwood forest in US
2. Indicator species
An indicator species is any biological species that defines a trait or characteristic of the environment. For example, a species may delineate an ecoregion or indicate an environmental condition such as a disease outbreak, pollution, species competition or climate change.
Examples; Lichens for air pollution (larger lichen population, sulfur dioxide in the air), fresh water shrimps and stonefly larvae for air quality.
3. Keystone species
A keystone species is a plant or animal that plays a unique and crucial role in the way an ecosystem functions. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether.
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.
Example, prairie dogs, mountain lions, hummingbirds, sea otter
4. Recognition species
The concept that a species is characterized by a unique fertilization system (the specific mate recognition system), which restricts gene-flow with other species. This changes the emphasis in the biological species concept from negative (not interbreeding with other species) to positive (breeding specifically with members of the same species).
Mainly based on fertilization system and behavior
Example Within a single habitat in the USA, as many as 30 or 40 different species of