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While talking about the evolution and conservation of dingoes in Australia, someone asked an interesting question:
Can I define the dingo as an endemic species?
That question, despite apparently simple, deals with some terminological conflicts and I must confess that I was not able to say yes or no at the moment.
As everybody knows, the dingoes (Canis lupus, but for some people Canis dingo1) were introduced in Australia by human beings, between 4,000 and 12,000 YBP. That being said, it's acceptable to define the dingo as an invasive, exotic species. Using Campbell's2 definition:
Invasive species: a species, often introduced by humans, that takes hold outside its native range.
However, some researchers argue that the dingoes, being isolated in Australia for a relatively long time, have a unique genetic profile. As this is controversial, let's suppose, just for the sake of the argument, that they do have a unique, distinctive genetic profile (and that they became a distinct species).
That being the case, the dingoes may be defined as endemic. Quoting Campbell again:
Endemic: referring to a species that is confined to a specific, relatively small geographic area.
I have taught biology for many years and I must confess that, for me, endemic and exotic were always opposite, mutually exclusive terms. However, in this case (and many others), it makes sense to say that the dingoes are exotic and endemic.
Maybe one can say that, from the moment the population became a distinct species on, it stopped to be exotic and started to be endemic, which would keep the two terms mutually exclusive.
So, my question is: can a given species (or population) be defined as exotic and endemic simultaneously?
PS: I'm not asking for opinions, which would make this question off topic for SE Biology. I'm asking for rules and guidelines in the use of the terms, preferably with references.
I think this partially depends on the timeframe. Endemism is usually divided into paleoendemism and neoendemism (see e.g. Kier er al in PNAS for use of both terms). Here, neoendemism is referring to the result of recent adaptive radiations that have led to new endemic species. This is then in contrast to paleoendemism, which refers to previously widespread species that are now confined to isolated areas.
Neoendemism is clearly related to your question, but whether dingos should be labelled as neoendemic depends on if it can be seen as a unique subspecies. If it is, it might be more suitable to view it as neoendemic and not exotic (nothing prohibits neoendemic species to be ecologically "problematic" to the previous fauna though).
In the literature (from what I've seen), neoendemism is usually used to describe historical events though (the result from adaptive radiations etc), so timeframe is obviously important (see e.g. Mishler er al, 2014). Even so, all taxa that has led to neoendemic species (through adaptations to local conditions) was by definition exotic at one point in time (e.g. when the most recent common ancestor of the Galapagos finches colonized the Galapagos islands). The same goes for the relatively recent adaptive radiation of Drosophila on Hawaii.
To me, neoendemic and invasive are not mutually exclusive terms, while the division between neoendemic and exotic may depend on time since colonization and whether the population now forms an independent taxon (e.g. subspecies) instead of a subpopulation still connected to its host population. I cannot find a reference or definition to support this interpretation right now though.
Endemism is the condition of being endemic, or 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 instance, entire families of different species of birds are endemic to the island of Madagascar. The term endemism can applied to many things, including diseases and natural phenomenon. Endemism in these cases refers to the “normal” or standard level of some measured observation within a specific geographic region or area.
Endemism is not to be confused with indigenous, a term which refers to the origins of a species. Indigenous refers to where a group originated. A species can be both endemic and indigenous to an area. However, some species thrive and exceed the bounds of their original indigenous location. This means that the species is no longer endemic, but is still indigenous to the original area. Once a species has reached a wide-spread, global distribution it is said to be cosmopolitan. Animals like whales, once indigenous to a specific mainland in the form of their 4-legged ancestors, are now cosmopolitan in distribution.
Types of Biodiversity
Scientists generally accept that the term biodiversity describes the number and kinds of species and their abundance in a given location or on the planet. Species can be difficult to define, but most biologists still feel comfortable with the concept and are able to identify and count eukaryotic species in most contexts. Biologists have also identified alternate measures of biodiversity, some of which are important for planning how to preserve biodiversity.
Genetic diversity is one of those alternate concepts. Genetic diversity , or genetic variation defines the raw material for evolution and adaptation in a species. A species’ future potential for adaptation depends on the genetic diversity held in the genomes of the individuals in populations that make up the species. The same is true for higher taxonomic categories. A genus with very different types of species will have more genetic diversity than a genus with species that are genetically similar and have similar ecologies. If there were a choice between one of these genera of species being preserved, the one with the greatest potential for subsequent evolution is the most genetically diverse one.
Many genes code for proteins, which in turn carry out the metabolic processes that keep organisms alive and reproducing. Genetic diversity can be measured as chemical diversity in that different species produce a variety of chemicals in their cells, both the proteins as well as the products and byproducts of metabolism. This chemical diversity has potential benefit for humans as a source of pharmaceuticals, so it provides one way to measure diversity that is important to human health and welfare.
Humans have generated diversity in domestic animals, plants, and fungi, among many other organisms. This diversity is also suffering losses because of migration, market forces, and increasing globalism in agriculture, especially in densely populated regions such as China, India, and Japan. The human population directly depends on this diversity as a stable food source, and its decline is troubling biologists and agricultural scientists.
It is also useful to define ecosystem diversity , meaning the number of different ecosystems on the planet or within a given geographic area (Figure 2). Whole ecosystems can disappear even if some of the species might survive by adapting to other ecosystems. The loss of an ecosystem means the loss of interactions between species, the loss of unique features of coadaptation, and the loss of biological productivity that an ecosystem is able to create. An example of a largely extinct ecosystem in North America is the prairie ecosystem. Prairies once spanned central North America from the boreal forest in northern Canada down into Mexico. They are now all but gone, replaced by crop fields, pasture lands, and suburban sprawl. Many of the species survive elsewhere, but the hugely productive ecosystem that was responsible for creating the most productive agricultural soils in the United States is now gone. As a consequence, native soils are disappearing or must be maintained and enhanced at great expense.
Figure 2. The variety of ecosystems on Earth—from (a) coral reef to (b) prairie—enables a great diversity of species to exist. (credit a: modification of work by Jim Maragos, USFWS credit b: modification of work by Jim Minnerath, USFWS)
Effect on Endemic Species
Lakes and islands are particularly vulnerable to extinction threats from introduced species. In Lake Victoria, the intentional introduction of the Nile perch was largely responsible for the extinction of about 200 species of cichlids (see Patterns of Biodiversity). The accidental introduction of the brown tree snake via aircraft (figure (PageIndex)) from the Solomon Islands to Guam in 1950 has led to the extinction of three species of birds and three to five species of reptiles endemic to the island. Several other species are still threatened. The brown tree snake is adept at exploiting human transportation as a means to migrate one was even found on an aircraft arriving in Corpus Christi, Texas. Constant vigilance on the part of airport, military, and commercial aircraft personnel is required to prevent the snake from moving from Guam to other islands in the Pacific, especially Hawaii. Islands do not make up a large area of land on the globe, but they do contain a disproportionate number of endemic species because of their isolation from mainland ancestors.
Figure (PageIndex): The brown tree snake, Boiga irregularis, is an exotic species that has caused numerous extinctions on the island of Guam since its accidental introduction in 1950. (credit: NPS)
Exotic Species: An exotic species refers to a plant, animal or microorganism species, which is introduced into an area outside of its native range.
Invasive Species: An invasive species refers to an exotic species whose introduction causes environmental and economic harm to the ecosystem.
Exotic Species: Exotic species are not harmful to ecosystems.
Invasive Species: Invasive species are harmful to ecosystems.
Exotic Species: Exotic species may require a lot of resources for the growth.
Invasive Species: Invasive species have a fast growth, rapid reproduction ability, and a high dispersal ability.
Natural Competitors or Enemies
Exotic Species: Exotic species may consist of natural competitors or enemies.
Invasive Species: Invasive species lack natural competitors or enemies.
Effect on Native Organisms
Exotic Species: Exotic species does not have an effect on native species.
Invasive Species: Invasive species may completely replace native species.
Exotic Species: Venus flytrap, purple beautyberry, voodoo lily, sensitive plant, cows, pigs, chicken, pigeons, mute swans, cats, and dogs are some examples of exotic plants.
Invasive Species: Kudzu, English ivy, feral cats, feral horses, lionfish, Asian carp, Japanese beetle, and cane toads are some examples of invasive species.
Exotic and invasive species are two types of non-native species, which are introduced to ecosystems by natural processes or humans. Most exotic species are domestic, and they do not harm ecosystems. But, invasive species are harmful to the ecosystems. The main difference between exotic and invasive species is their effect on the ecosystem.
1. “Introduction of Exotic Species.” NatureWorks, Available here.
2. Carol, Max. “What is an invasive species?” TreeHugger, 12 Sept. 2017, Available here.
1. “Mimosa pudica 003” By H. Zell – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Mexilhão-zebra” By Amy Benson – U.S. Geological Survey (CC0) via Commons Wikimedia
3. “Kudzu” by NatureServe (CC BY 2.0) via Flickr
About the Author: Lakna
Lakna, a graduate in Molecular Biology & Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things
Difference Between Exotic and Invasive species
Exotic and invasive species have not been well understood even by some of the science graduates due to the lack of scientific acumen. Unless the definitions of these terms are not sorted out correctly, the actual meaning would not be easy to understand, especially when there are two species with one being an exotic and the other being an invasive. The main reason for this confusion is that both invasive and exotic species are involved in living outside the natural distribution range. This article aims to emphasize the important difference between invasive and exotic species.
Exotic species could be defined as any organism that happens to live outside its natural distribution range as a consequence of anthropogenic activity, or activities through deliberate or accidental introduction to a new habitat. The primary understanding about an exotic species is that, it is a non-native or non-indigenous in its new location. They are also known as alien species, as some authors refer. An exotic species could be a plant, an animal, or a bacterium. Since it is related with the distribution range of a particular species, an exotic species to one place would not be exotic to another. In fact, a native species of one particular habitat could become an exotic species in another. However, there are many ways of occurring exotic species in a particular area, ecosystem, or habitat deliberate introduction could take place as a mean for agricultural or livestock production and controlling pest or nuisance species. Alien species are capable of successfully competing for the natural resources with the native species mostly due the lack of natural predators in the new habitat, and they could become invasive if the reproduction could take place. There are situations in which the biodiversity and bio-productivity have increased after introducing of exotic species into natural habitats the introduction of some exotic plant species in New Zealand from North America has been beneficial for the vegetation and biodiversity of the particular habitat. However, in many places of the world, the exotic species have not been friendly with the environment and cause to become invasive.
Invasive species have been one of the major problems for the environment, ecology, and economy of many places. According to the definition, an exotic species becomes invasive when the population starts to increase through reproduction that happens because there are no natural enemies in the new habitat. It is a serial process of becoming invasive from exotic, involving few steps starting from the introduction, survival, reproduction, thriving, and invading. After an exotic species is being introduced into a new habitat deliberately or accidentally, the already existing occupied ecological niches might prey upon it. If the exotic species could survive, the ability to compete for resources and the possibility for production to take place would start to matter them. Usually, the introduced species are greatly capable of successfully compete over others, as there are no natural competitors and enemies. When they can start to breed, the population grows without breaks. Therefore, they start to thrive and become dominant with the invasion of the environment. That can cause many problems to the naturally evolved ecosystems, as the natural species face food spatial crises. The ecosystem loses the delicate balance of energy flow after that, and it can lead to detrimental effects. These consequences could cause the agriculture and other human related activities also to go down. Therefore, the exotic species should be seriously considered prior to introduction, as the consequences may be serious.
What is the difference between Exotic and Invasive species?
• Both are non-native species occurring in a particular area, but exotic species may or may not raise concerns, while invasive species always raise serious concerns on many aspects.
• Exotic species could be either wild or captive, while they would become invasive in wild.
• Exotic species may or may not have natural competitors and enemies, whereas invasive species do not have any danger of such barriers.
Chapter 16 Quiz (Combined)
C. regulating the chemistry of the planet's atmosphere.
D. pollinating the crops humans depend on for food.
A. ecological diversity and species diversity
B. number of endemic species and degree of threat
C. species richness and ecosystem integrity
D. size and distance from nearest alternative hotspot
A. a significant reservoir of biological diversity.
B. an area encompassing the tropical rainforests of South America and southeast Asia.
C. a highly threatened area.
D. All of the above are correct.
A. is an inexact, value-laden science.
B. is a multidisciplinary science.
C. often requires making decisions in the absence of complete information.
D. requires eternal vigilance.
A. increases as you move away from the equator in both terrestrial and marine ecosystems.
B. is not predictable relative to how close an ecosystem is to the equator.
C. decreases as you move away from the equator in marine ecosystems, but increases as you move away from the equator in terrestrial ecosystems.
D. decreases as you move away from the equator in terrestrial ecosystems, but increases as you move away from the equator in marine ecosystems.
Saving lonely species is important for environment
The lemur, Javan rhino and Santa Cruz kangaroo rat are all lonesome animals. As endemic species, they live in habitats restricted to a particular area due to climate change, urban development or other occurrences.
Endemic species are often endangered, and a University of Tennessee, Knoxville, study finds that saving them is more important to biodiversity than previously thought.
Joe Bailey, associate professor in the Department of Ecology and Evolutionary Biology, and his colleagues from the University of Tasmania in Australia looked at endemic eucalyptus found in Tasmania. They discovered that these rare species have developed unique characteristics to survive, and that these characteristics may also impact the survival of its neighbors in the ecosystem.
The findings are published in the academic journal PLOS One.
Using experimental forestry trials where plants were taken from the wild and replanted in a single location, the researchers investigated whether the evolution of endemic species was an important process that altered species interactions. The study is one of the first to compare the functions of endemic and nonendemics in an experimental setting.
The team discovered that these eucalypts have evolved traits that allow them to persist in harsh conditions where many other species can't. These traits include thick leaves that stay on the tree a long time. Much as we conserve money when times are tight, this growth strategy allows these plants to minimize the resources they invest in leaves. The leaves also lack nutrition and are hard to digest, making them unappealing to most herbivores. Variation in such characteristics can impact the entire ecosystem.
"Because endemic species' genes and traits are different relative to nonendemic species, the web of interactions those genes support is also different," said Bailey. "Therefore, the losses of those genes from ecosystems will likely ripple through and hurt the species interactions they create."
For example, the change in the eucalyptus leaves can negatively impact the specialist herbivores that adapted to the plants by negatively affecting their ability to find food and thus survive.
The study results contribute to a growing body of research that shows genes in plants can have direct and indirect effects on other species in the ecosystem. This has important implications for the conservation of biodiversity, as the loss of endemics as a group might also represent the loss of novel ecological interactions. These results are particularly important in the context of climate change.
"In the midst of a biodiversity crisis where species extinction rates are a hundred to a thousand times greater than the natural rate of extinction, understanding the biology of rare and endemic species is a priority rather than a pursuit of novelty," said Bailey, who added that endemic species act also as a repository for rare genes.
Preventing the extinction of such species should be a priority of the scientific community and the general public who enjoy nature, noted Bailey.
Indigenous species are categorized as being a type of native species. Rather than being confined to a specific area, indigenous species tend to be more widely dispersed and adaptable. Because of the unique evolutionary processes they have undergone indigenous plants and animals are considered to be strong enough to adjust to diverse surroundings and can spring back to life in areas in which they had previously disappeared. This re-population can be achieved either through natural means or by way of human intervention.
Organisms can be indigenous to a variety of places at the same time and therefore not limited by area or the time period in which they exist. If, for example, a particular species can be found in a variety of regions throughout the world it is classified as being indigenous to those specific areas rather than being deemed as endemic.
An example of an indigenous animal species is the beaver. This large rodent is native to regions of North America, Europe, and Asia. Although in parts of North America beavers have suffered from over hunting and as a result have nearly disappeared from the local landscape in more recent years the species has begun to naturally return to states it was once more plentiful such as New York and Illinois. Humans have also been responsible for artificially relocating beavers to non-native lands by introducing the species to South American countries such as Argentina and Chile.
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