An endemic species is one whose habitat is restricted to a particular area. The term could refer to an animal, a plant, a fungus, or even a microorganism. The definition differs from “indigenous,” or “native,” species in that the latter, although it occurs naturally in an area, is also found in other areas. Endemic species are often endangered, and particular examples may become a focus point for campaigns to protect biodiversity in a given environment. Some have become national, or regional, emblems.
The term can sometimes be used relatively. A species may be said to be endemic to one tiny area or to a large land mass, such as Australia. When it comes to birds, which are less land-bound than mammals or other animals, biologists might use slightly different terms to talk about what habitats a bird is “endemic” to. Bird experts talk about Endemic Bird Areas or EBAs that represent the total habitat for a bird species. An EBA may include temporary habitats or regions for a bird, as migration patterns broaden the spaces that bird types live in.
How Endemic Species Arise
There are two ways in which a species may come to be endemic to a particular area. An initially widely distributed population may disappear from many of its habitats, due to changes which have occurred. These could be climate changes, an influx of predators, or human activities. Eventually, the organism may be confined to just one area: this type is known as a paleoendemic species. A good example is the giant sequoia tree, which used to be found over large parts of North America, but is now confined to a small part of California.
Alternatively, various factors could cause two populations of a given species to become isolated from one another. For example, as a result of plate tectonics, a continent may split apart, forming two new continents, each with its own population of a given organism. Over long periods of time, these two populations evolve differently, because they cannot interbreed with one another, and eventually they are sufficiently different from one another to be classified as separate species. These are known as neoendemic species. In some cases, where a population has been isolated for a very long time, the members may look very different from anything elsewhere on the planet; for example, Australia has a number of unique animals, such as kangaroos and koala bears.
Determining whether a species is paleoendemic or neoendemic may not always be easy. Occasionally, when an organism has declined in relatively recent times, it is known from historical records that it was once more widely distributed. In other cases, this can be determined from fossil records, but this depends on such evidence being available — it requires exposed rocks of the right age and type to preserve identifiable fossil remains. An organism may be classed as neoendemic if there is no evidence of it having ever existed outside its current range. Such species may sometimes have specific adaptations for some unique aspect of their habitat.
Endemic Species and Evolution
Many classic examples of neoendemic species can be found on the Galapagos Islands, 600 miles (966 kilometers) off the coast of Ecuador in South America. One example is the marine iguana, a lizard that has evolved to adapt to a coastal environment, and is the only type of lizard that can swim. When Charles Darwin visited the islands in 1835, he made a study of the different types of finch that he found. He noticed that they had different types of beaks, each ideally adapted to a particular type of food, such as nuts or fruit. He concluded that they had all originated from one type that had reached the islands from the mainland a long time ago, and had since then diversified over many generations; it was these observations that led to his theory of evolution.
Biogeography
The study of endemic species is part of a wider subject called biogeography. This encompasses all the factors affecting the distribution of organisms on the planet; for example climates and microclimates, soil types, ecology, and human activities. Biogeographical zones can be defined for endemic organisms, and understanding these can help biologists to decipher the past of a type of animal or plant, and predict its future.
Threats and Protection
Since they are often confined to very small areas, and sometimes to unusual and sensitive habitats within these localities, many endemic species are endangered. Among the threats they face are land use by humans for agriculture or building, and invasive species introduced either intentionally or accidentally. Biogeographical studies can be a way for biologists to defend a dwindling organism against encroachment on its habitat from human communities or commercial activity. A life form whose sole habitat is under attack can be classified as an endangered species. If the total population is below a certain number, it might be classified as critically endangered.
Biologists and biogeographers looking at species' habitats may be part of an effort to protect a certain environment against local development plans. In some cases, a major public campaign may be launched, aimed at protecting such a habitat from development, but this is more likely for animals that are considered beautiful or cute. In the case of an obscure beetle or fungus, a biologist or research group may be the only force involved in attempts to save an endangered endemic species.