What is Endemism?
Endemism is the condition of being endemic or of being restricted in geographical distribution to an area or region. The area or region can vary in size and is defined or identified in different ways. Endemism is an ecological classification in that it describes the range or distribution of a species or group of species.
For example, entire families of different species of birds are endemic to the island of Madagascar. The term endemism can be applied to many things, including diseases and natural phenomena. Endemism in these cases refers to the “normal” or standard level of measured observation within a particular geographic region or area.
Endemism is not to be confused with indigenism, a term that refers to the origin of a species. Indigenous refers to the origin of a group. A species can be both endemic and native to an area. However, some species thrive and exceed the limits of their original indigenous habitat.
This means that the species is no longer endemic, but is still native to the original area. Once a species has achieved widespread, worldwide distribution, it is referred to as cosmopolitan. Animals like whales, which were once native to a certain mainland in the form of their four-legged ancestors, are now cosmopolitan.
What is Endemic Species?
An endemic species is a species that is geographically restricted to a specific area. Endemism in one species can result from the extinction of a species in other regions. This is called paleo-demism.
Alternatively, new species are always endemic to the region where they first appear. This is called neo-demism. Both forms of endemism are discussed in more detail below in “Types of Endemism”.
Endemic species, regardless of how they were restricted to a particular area, face the same threats to their existence. The smaller the region, the greater the threat to the survival of the species.
Any action that reduces or in any way divides the size of the land can significantly affect the normal patterns of endemic species. While endemism and endangerment or threat are different things, endemic in a small area is often a red flag that a species may be threatened or endangered.
This is not always the case, as many species that are found around the world are also considered threatened or endangered. Many sharks have joined the list in recent years. While they are dispersed in many ocean waters, harvesting shark fins for soup has decimated their populations worldwide.
Endemism sometimes protects species from global exploitation simply because the species only exists in a small area. This can even make it easier to protect the species, as the land can be placed under conservation measures to limit construction and human impact on the land.
What is Endemic Disease?
Scientists studying epidemiology or disease outbreaks have a similar definition of endemism. An endemic disease is a disease that occurs in constant amounts in a specific location. For example, endemic relapsing fever is a disease that occurs in Europe and North America.
The disease is not seen in any observable amount in other parts of the world. Other diseases that are new to an area or that are rapidly increasing in prevalence are known as epidemic diseases.
There are many endemic diseases, and their endemism has roots in the species and vectors that promote these diseases. In the case of recurrent fever, a vector carries the bacterium of the Borrelia species.
There are several vectors that can carry these bacteria, mainly ticks, and lice. The types of ticks and lice that carry these bacteria are endemic to the northern hemisphere. Borrelia bacteria are also responsible for Lyme disease, a disease endemic to the northern hemisphere. A map of Lyme disease is shown below and corresponds to the endemism seen in tick and lice species.
While Lyme disease and recurrent fever are endemic to these areas, they are not endemic to say Australia. If there were few cases of Lyme disease in Australia, the disease would be considered epidemic as the normal extent of Lyme disease in Australia is zero.
What are the Types of Endemism?
There are two basic ways for a species to show endemism in a given region. Basically, the difference between the two is whether the species is newly emerging or historical and declining. Paleo-demism describes the later. In this form of endemism, a once widespread species has been reduced to a much smaller range. This is the case with many large predators today.
Before humans, large predators were common around the world. As human society became more organized, large predators were driven out of society and out of their historical realms. Those that did not become extinct are now confined to limited areas.
Conservation efforts for these animals are focused on protecting the current range and extending it to the historical range. However, this is difficult as humans are often opposed to the reintroduction of large predators. Without protection from hunters, the species are easily pushed back into their endemic range.
On the other hand, new species branch out from the evolution tree every day. These species are both endemic and native to the place where they first appeared. They’re limited to one geographic location just because they started there. This is known as neo-demism. There are many species on islands that show this form of endemism.
Islands offer interesting and isolated grounds for new species to develop. While the species are now endemic to the island, their ancestors probably weren’t. Take the Galapagos finches as an example.
The Galapagos Archipelago contains many islands. Thousands of years ago a single species of finch came to the islands. It initially spread across the island as a species. However, evolution has now separated the birds so much that they represent different species. The differences in vegetation on the islands divided the ancestors into many smaller species that show endemism to the island where they are found.
What is the Examples of Endemic species?
There are several ways that a species can become endemic to a given area. A widely dispersed population can disappear from multiple habitats due to changes in their natural habitat. The changes could be an influx of predators, human activity, climate change, or a combination of these factors.
All other organisms of a species that were widespread around the world begin to die out until the species is restricted to only one region.
For example, Endemic species such as the turtles of the Galapagos Islands and the lemurs of Madagascar can be found on small islands. Large islands also offer the same isolation, but on a larger scale.
Antarctica, Hawaii, and Australia are huge land masses where we can find many endemic species. For example, kangaroos are endemic to Australia and polar bears are endemic to the Arctic.
In endemic plants, species sometimes become endemic due to habitat destruction. The Redwood Forest on the west coast of the United States has become endemic as it is now almost entirely restricted to California. While there was a time when redwoods covered much of the United States, logging destroyed them and is now confined to a small nature reserve.
On the other hand, diseases can also be endemic. An endemic disease can be geographically isolated or it can be assigned to a specific group. Malaria is an example of an endemic disease as it is mostly limited to small pockets of infection in Africa.