Endemic Species

What is the Definition of Endemic Species?

For starters, let's look at the definition of an endemic species.

Species can be endemic to a continent, region, or even a specific island. Species that are not endemic are called generalists; such live in many different geographic areas.

Endemic species tend to be isolated in some way such that the species are unable to spread to other areas. They may also be adapted to the unique conditions of their habitat, making it difficult for them to survive in other environmental conditions. For this reason, endemism tends to occur in isolated landmasses.

For example, most of the naturally occurring species in the Hawaiian Islands, the Australian continent, and the southern tip of Africa are endemic because of the geographic isolation of these areas. On the contrary, the number of endemic species in less isolated regions such as Europe and North America tends to be low.

How is the Concept of Endemic Species Different from other Related Concepts (endangered, native, and exotic)?

To deepen our understanding of the concept of endemic species, it is helpful to distinguish it from similar or related concepts. Here we will differentiate endemic from endangered, native, and exotic.

Difference Between Endemic and Endangered species

Now, let's look at the definition of an endangered species, and how it differs from an endemic species.

Alongside “critically endangered” and “vulnerable”, it falls within the “threatened” category according to the assessment process of the International Union for Conservation of Nature and Natural Resources (IUCN). The IUCN is an organization that maintains a Red List of extinct and endangered species. The IUCN Red List is considered the most comprehensive data bank on the conservation status of various plant, animal, and fungi species.

While there are endemic species that can be assessed as endangered by the IUCN, not all endemic species are endangered. Likewise, not all endangered species are endemic species. We will discuss examples of endemic species and their conservation status later on in the article.

Difference between Endemic and Native species

But, what are native species? How do they differ from endemic species? Let's find out!

A species that is native to an area means that no human intervention was involved in its distribution in that area. For example, the koala is native to Australia; it was not introduced by humans; rather, fossil evidence shows that the koala as a species evolved in Australia around 25 million years ago from an ancestor that it shares with the wombat.

Endemic species are a subcategory of native species: all endemic species are native to their specific geographic range. But–unless their geographic range is limited to a specific area–not all native species are endemic species.

Difference between Endemic and Exotic species

Last but not least, let's look at the difference between endemic and exotic species.

For example, the English Ivy (Hedera helix) is quite common in the US where it is usually sold as an ornamental plant; however, it is actually native to Europe, Western Asia, and Northern Africa, and it is exotic to the US.

Why Are Endemic Species Vulnerable To Extinction?

Due to their limited geographic range, the probability of becoming endangered or extinct is much higher for endemic species.

Because threats to species–especially those posed by humans (for example, hunting and habitat destruction)--tend to be localized, species that inhabit larger geographic areas have a higher chance of survival even if some populations are threatened in certain areas. On the contrary, endemic species that face a local threat do not have reserve populations elsewhere, making them more vulnerable to extinction.

Relatively small geographic areas with a lot of endemic species that are endangered are called biodiversity hotspots. To illustrate, about 30% of all species of birds are found in hotspots that constitute only around 2% of the total land area of the world. This means, when a biodiversity hotspot is threatened, there is a risk of losing a massive amount of species diversity. As such, biodiversity hotspots are considered priority areas for conservation.

In addition to geographic isolation, endemic species can also be more vulnerable to extinction due to genetic factors. A small population is prone to losing genetic variation due to inbreeding and genetic drift, pulling the population into an extinction vortex, where the population shrinks until no more individuals survive.

Inbreeding is when closely-related individuals reproduce. Offspring produced through inbreeding have little genetic variation, making them more prone to diseases and defects. They are also more likely to suffer from genetic conditions caused by inheriting two recessive alleles.

Genetic drift is when chance events cause changes in allele frequencies. Unlike natural selection, where individuals with traits that help them survive in their environment can have more offspring because of those traits, genetic drift causes allele frequencies to change at random.

If conditions are stable, the population may survive. However, if conditions change–due to the emergence of infectious diseases, for instance–the population may be unable to cope. This is because with less genetic variation it is less likely that there are individuals with the traits needed to survive under the new conditions.

What Are Examples Of Endemic Species And Their Conservation Status?

In this section, we will discuss some examples of endemic species, their characteristics, and their conservation status according to the assessments made by the IUCN.

Emperor penguin (Aptenodytes forsteri)

The Emperor penguin is a penguin species that is endemic to Antarctica. It is highly dependent on Antarctic land-fast sea ice (sea ice that is attached to the coastline, shore, or ocean bottom) which it uses as a breeding ground, as well as pack ice (floating mass of ice) which it uses as foraging ground.

The IUCN lists the Emperor Penguin as “near threatened” because it is anticipated that its population will rapidly decline due to the gradual loss of Antarctic sea ice over the next decades.

Tasmanian Devil (Sarcophilus harrisii)

The Tasmanian Devil is endemic to Tasmania, Australia. The IUCN lists the Tasmanian Devil as “endangered”. While it is threatened by road hazards, dog kills, and persecution (killed by individuals who regarded the Tasmanian Devils as pests that harm or kill livestock), the primary threat to its survival is the Devil Facial Tumor Disease (DFTD).

DFTD is thought to be an infectious and widespread disease, which allows it to spread fast and affect a large portion of local populations.

California redwood (Sequoia sempervirens)

The California redwood is endemic to the Pacific coast region from southwestern Oregon to northern California. While the population is still large, the IUCN lists the California Redwood as “endangered” not necessarily due to concerns regarding the survival in the wild of the species, but more so due to the decline of old-growth redwood forests.