Endemism is the state of a species being found only in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsewhere. [1] For example, the Cape sugarbird is found exclusively in southwestern South Africa and is therefore said to be endemic to that particular part of the world. [2] An endemic species can also be referred to as an endemism or, in scientific literature, as an endemite.[ citation needed ] Similarly many species found in the Western ghats of India are examples of endemism.
Endemism is an important concept in conservation biology for measuring biodiversity in a particular place and evaluating the risk of extinction for species. Endemism is also of interest in evolutionary biology, because it provides clues about how changes in the environment cause species to undergo range shifts (potentially expanding their range into a larger area, or becoming extirpated from an area they once lived), go extinct, or diversify into more species. [3]
The extreme opposite of an endemic species is one with a cosmopolitan distribution, having a global or widespread range. [1]
A rare alternative term for a species that is endemic is "precinctive", which applies to species (and other taxonomic levels) that are restricted to a defined geographical area. [4] Other terms that sometimes are used interchangeably, but less often, include autochthonal, autochthonic, and indigenous; however, these terms do not reflect the status of a species that specifically belongs only to a determined place.
The word endemic is from Neo-Latin endēmicus, from Greek ἔνδημος, éndēmos, "native". Endēmos is formed of en meaning "in", and dēmos meaning "the people". [5] The word entered the English language as a loan word from French endémique, and originally seems to have been used in the sense of diseases that occur at a constant amount in a country, as opposed to epidemic diseases, which are exploding in cases. The word was used in biology in 1872 to mean a species restricted to a specific location by Charles Darwin. [6]
The more uncommon term 'precinctive' has been used by some entomologists as the equivalent of 'endemic'. [4] [6] [7] Precinctive was coined in 1900 by David Sharp when describing the Hawaiian insects, as he was uncomfortable with the fact that the word 'endemic' is often associated with diseases. [8] 'Precinctive' was first used in botany by Vaughan MacCaughey in Hawaii in 1917. [9]
A species is considered to be endemic to the area where it is found naturally, to the exclusion of other areas; presence in captivity or botanical gardens does not disqualify a species from being endemic.[ citation needed ] In theory, the term "endemic" could be applied on any scale; for example, the cougar is endemic to the Americas, [1] and all known life is endemic to Earth. However, endemism is normally used only when a species has a relatively small or restricted range. This usage of "endemic" contrasts with "cosmopolitan." Endemics are not necessarily rare; some might be common where they occur. Likewise, not all rare species are endemics; some may have a large range but be rare throughout this range. [10]
The evolutionary history of a species can lead to endemism in multiple ways. Allopatric speciation, or geographic speciation, is when two populations of a species become geographically separated from each other and as a result develop into different species. [1] In isolated areas where there is little possibility for organisms to disperse to new places, or to receive new gene flow from outside, the rate of endemism is particularly high. For example, many endemic species are found on remote islands, such as Hawaii, the Galápagos Islands and Socotra. [11] Populations on an island are isolated, with little opportunity to interbreed with outside populations, which eventually causes reproductive isolation and separation into different species. Darwin's finches in the Galápagos archipelago are examples of species endemic to islands. [12] Similarly, isolated mountainous regions like the Ethiopian Highlands, [13] or large bodies of water far from other lakes, like Lake Baikal, can also have high rates of endemism. [14]
Endemism can also be created in areas which act as refuges for species during times of climate change like ice ages. These changes may have caused species to become repeatedly restricted to regions with unusually stable climate conditions, leading to high concentrations of endemic species in areas resistant to climate fluctuations. [15] Endemic species that used to exist in a much larger area, but died out in most of their range, are called paleoendemic, in contrast to neoendemic species, which are new species that have not dispersed beyond their range. The ginkgo tree, Ginkgo biloba , is one example of a paleoendemic species. [16]
In many cases biological factors, such as low rates of dispersal or returning to the spawning area (philopatry), can cause a particular group of organisms to have high speciation rates and thus many endemic species. For example, cichlids in the East African Rift Lakes have diversified into many more endemic species than the other fish families in the same lakes, possibly due to such factors. [14] Plants that become endemic on isolated islands are often those which have a high rate of dispersal and are able to reach such islands by being dispersed by birds. [17] While birds are less likely to be endemic to a region based on their ability to disperse via flight, there are over 2,500 species which are considered endemic, meaning that the species is restricted to an area less than five million hectares (twelve million acres). [18]
Microorganisms were traditionally not believed to form endemics. The hypothesis 'everything is everywhere', first stated in Dutch by Lourens G.M. Baas Becking in 1934, describes the theory that the distribution of organisms smaller than 2 mm is cosmopolitan where habitats occur that support their growth. [19]
Endemism can reflect a wide variety of evolutionary histories, so researchers often use more specialized terms that categorize endemic species based upon how they came to be endemic to an area. [3] Different categorizations of endemism also capture the uniqueness and irreplaceability of biodiversity hotspots differently and impact how those hotspots are defined, affecting how resources for conservation are allocated. [20]
The first subcategories were first introduced by Claude P. E. Favager and Juliette Contandriopoulis in 1961: schizoendemics, apoendemics and patroendemics. [10] [21] Using this work, Ledyard Stebbins and Jack Major then introduced the concepts of neoendemics and paleoendemics in 1965 to describe the endemics of California. [22] Endemic taxa can also be classified into autochthonous, allochthonous, taxonomic relicts and biogeographic relicts. [1]
Paleoendemism refers to species that were formerly widespread but are now restricted to a smaller area. Neoendemism refers to species that have recently arisen, such as through divergence and reproductive isolation [14] or through hybridization [ citation needed ] and polyploidy in plants, [23] and have not dispersed beyond a limited range. [14]
Paleoendemism is more or less synonymous with the concept of a 'relict species': a population or taxon of organisms that were more widespread or more diverse in the past. A 'relictual population' is a population that currently occurs in a restricted area, but whose original range was far wider during a previous geologic epoch. Similarly, a 'relictual taxon' is a taxon (e.g. species or other lineage) that is the sole surviving representative of a formerly diverse group. [24]
The concept of phylogenetic endemism has also been used to measure the relative uniqueness of the species endemic to an area. In measurements that incorporate phylogenetic endemism, branches of the evolutionary tree are weighted by how narrowly they are distributed. This captures not only the total number of taxa endemic to the area (taxonomic endemism), but also how distant those species are from their living relatives. [3] [20]
Schizoendemics, apoendemics and patroendemics can all be classified as types of neoendemics. Schizoendemics arise from a wider distributed taxon that has become reproductively isolated without becoming (potentially) genetically isolated – a schizoendemic has the same chromosome count as the parent taxon it evolved from. An apoendemic is a polyploid of the parent taxon (or taxa in the case of allopolyploids), whereas a patroendemic has a lower, diploid chromosome count than the related, more widely distributed polyploid taxon. [17] [23] Mikio Ono coined the term 'aneuendemics' in 1991 for species that have more or fewer chromosomes than their relatives due to aneuploidy. [17]
Pseudoendemics are taxa that have possibly recently evolved from a mutation. Holoendemics is a concept introduced by Richardson in 1978 to describe taxa that have remained endemic to a restricted distribution for a very long time. [10]
In a 2000 paper, Myers and de Grave further attempted to redefine the concept. In their view, everything is endemic, even cosmopolitan species are endemic to Earth, and earlier definitions restricting endemics to specific locations are wrong. Thus the subdivisions neoendemics and paleoendemics are without merit regarding the study of distributions, because these concepts consider that an endemic has a distribution limited to one place. Instead, they propose four different categories: holoendemics, euryendemics, stenoendemics and rhoendemics. In their scheme cryptoendemics and euendemics are further subdivisions of rhoendemics. In their view, a holoendemic is a cosmopolitan species. Stenoendemics, also known as local endemics, [10] have a reduced distribution and are synonymous with the word 'endemics' in the traditional sense, whereas euryendemics have a larger distribution -both these have distributions that are more or less continuous. A rhoendemic has a disjunct distribution. Where this disjunct distribution is caused by vicariance, in a euendemic the vicariance was geologic in nature, such as the movement of tectonic plates, but in a cryptoendemic the disjunct distribution was due to the extinction of the intervening populations. There is yet another possible situation that can cause a disjunct distribution, where a species is able to colonize new territories by crossing over areas of unsuitable habitat, such as plants colonizing an island – this situation they dismiss as extremely rare and do not devise a name for. Traditionally, none of Myers and de Grave's categories would be considered endemics except stenoendemics. [19] [25]
Some environments are particularly conducive to the development of endemic species, either because they allow the persistence of relict taxa that were extirpated elsewhere, or because they provide mechanisms for isolation and opportunities to fill new niches. [15]
Serpentine soils act as 'edaphic islands' of low fertility and these soils lead to high rates of endemism. [26] [27] These soils are found in the Balkan Peninsula, Turkey, Alps, Cuba, New Caledonia, South Africa, Zimbabwe, the North American Appalachians, and scattered distribution in California, Oregon, and Washington and elsewhere. [28] For example, Mayer and Soltis considered the widespread subspecies Streptanthus glandulosus subsp. glandulosus which grows on normal soils, to be a paleoendemic, whereas closely related endemic forms of S. glandulosus occurring on serpentine soil patches are neoendemics which recently evolved from subsp. glandulosus. [27]
Obligate cave-dwelling species, known as troglobites, are often endemic to small areas, even to single individual caves, because cave habitats are by nature restricted, isolated, and fragmented. [29] [30] A high level of adaptation to a cave environment limits an organism's ability to disperse, since caves are often not connected to each other. One hypothesis for how closely related troglobite species could become isolated from one another in different caves is that their common ancestor may have been less restricted to cave habitats. When climate conditions became unfavorable, the ancestral species was extirpated from the surface, but some populations survived in caves, and diverged into different species due to lack of gene flow between them. [31]
Isolated islands commonly develop a number of endemics. [17] [32] Many species and other higher taxonomic groups exist in very small terrestrial or aquatic islands, which restrict their distribution. The Devil's Hole pupfish, Cyprinodon diabolis, has its whole native population restricted to a spring that is 20 x 3 meters, in Nevada's Mojave Desert. [33] This 'aquatic island' is connected to an underground basin; however, the population present in the pool remains isolated.
Other areas very similar to the Galapagos Islands of the Pacific Ocean exist and foster high rates of endemism. The Socotra Archipelago of Yemen, located in the Indian Ocean, has seen a new endemic species of parasitic leech, Myxobdella socotrensis, appear. [34] This species is restricted to freshwater springs, where it may attach to and feed upon native crabs.
Mountains can be seen as 'sky islands': refugia of endemics because species that live in the cool climates of mountain peaks are geographically isolated. For example, in the Alpes-Maritimes department of France, Saxifraga florulenta is an endemic plant that may have evolved in the Late Miocene and could have once been widespread across the Mediterranean Basin. [35]
Volcanoes also tend to harbor a number of endemic species. Plants on volcanoes tend to fill a specialized ecological niche, with a very restrictive range, due to the unique environmental characteristics. The Kula Volcano, one of the fourteen volcanoes in Turkey, is home to 13 endemic species of plants. [36]
Endemics might more easily become endangered or extinct because they are already restricted in distribution. [37] This puts endemic plants and animals at greater risk than widespread species during the rapid climate change of this century. [38] [39] Some scientists claim that the presence of endemic species in an area is a good method to find geographical regions that can be considered priorities for conservation. [1] [40] Endemism can thus be studied as a proxy for measuring biodiversity of a region. [41]
The concept of finding endemic species that occur in the same region to designate 'endemism hotspots' was first proposed by Paul Müller in a 1973 book. According to him, this is only possible where 1.) the taxonomy of the species in question is not in dispute; 2.) the species distribution is accurately known; and 3.) the species have relatively small distributional ranges. [42] [43]
In a 2000 article, Myers et al. used the standard of having more than 0.5% of the world's plant species being endemic to the region to designate 25 geographical areas of the world as biodiversity hotspots. [40]
In response to the above, the World Wildlife Fund has split the world into a few hundred geographical 'ecoregions'. These have been designed to include as many species as possible that only occur in a single ecoregion, and these species are thus 'endemics' to these ecoregions. [14] Since plenty of these ecoregions have a high prevalence of endemics existing within them, many National Parks have been formed around or within them to further promote conservation. The Caparaó National Park was formed in the Atlantic Forest, a biodiversity hotspot located in Brazil, in order to help protect valuable and vulnerable species. [44]
Other scientists have argued that endemism is not an appropriate measure of biodiversity, because the levels of threat or biodiversity are not actually correlated to areas of high endemism. When using bird species as an example, it was found that only 2.5% of biodiversity hotspots correlate with endemism and the threatened nature of a geographic region. [1] [45] A similar pattern had been found regarding mammals, Lasioglossum bees, Plusiinae moths, and swallowtail butterflies in North America: these different groups of taxa did not correlate geographically with each other regarding endemism and species richness. Especially using mammals as flagship species proved to be a poor system of identifying and protecting areas of high invertebrate biodiversity. [46] In response to this, other scientists again defended the concept by using WWF ecoregions and reptiles, finding that most reptile endemics occur in WWF ecoregions with high biodiversity. [41]
Other conservation efforts for endemics include keeping captive and semi-captive populations in zoological parks and botanical gardens. These methods are ex situ ("off-site") conservation methods. The use of such methods may not only offer refuge and protection for individuals of declining or vulnerable populations, but it may also allow biologists valuable opportunities to research them as well.
The Palearctic or Palaearctic is the largest of the eight biogeographic realms of the Earth. It stretches across all of Eurasia north of the foothills of the Himalayas, and North Africa.
The Western Ghats, also known as the Sahyadri, is a mountain range that stretches 1,600 km (990 mi) along the western coast of the Indian peninsula. Covering an area of 160,000 km2 (62,000 sq mi), it traverses the states of Gujarat, Maharashtra, Goa, Karnataka, Kerala, and Tamil Nadu. The range forms an almost continuous chain of mountains along the western edge of the Deccan Plateau, from the Tapti River to Swamithoppe in Kanyakumari district at the southern tip of the Indian peninsula. The Western Ghats meet with the Eastern Ghats at Nilgiris before continuing south.
Allopatric speciation – also referred to as geographic speciation, vicariant speciation, or its earlier name the dumbbell model – is a mode of speciation that occurs when biological populations become geographically isolated from each other to an extent that prevents or interferes with gene flow.
A tepui, or tepuy, is a table-top mountain or mesa found in South America, especially in Venezuela and western Guyana. The word tepui means "house of the gods" in the native tongue of the Pemon, the indigenous people who inhabit the Gran Sabana.
A biodiversity hotspot is a biogeographic region with significant levels of biodiversity that is threatened by human habitation. Norman Myers wrote about the concept in two articles in The Environmentalist in 1988 and 1990, after which the concept was revised following thorough analysis by Myers and others into "Hotspots: Earth's Biologically Richest and Most Endangered Terrestrial Ecoregions" and a paper published in the journal Nature, both in 2000.
Peripatric speciation is a mode of speciation in which a new species is formed from an isolated peripheral population. Since peripatric speciation resembles allopatric speciation, in that populations are isolated and prevented from exchanging genes, it can often be difficult to distinguish between them., and peripatric speciation may be considered one type or model of allopatric speciation. The primary distinguishing characteristic of peripatric speciation is that one of the populations is much smaller than the other, as opposed to allopatric speciation, in which similarly-sized populations become separated. The terms peripatric and peripatry are often used in biogeography, referring to organisms whose ranges are closely adjacent but do not overlap, being separated where these organisms do not occur—for example on an oceanic island compared to the mainland. Such organisms are usually closely related ; their distribution being the result of peripatric speciation.
The biodiversity of New Caledonia is of exceptional biological and paleoecological interest. It is frequently referred to as a biodiversity hotspot. The country is a large South Pacific archipelago with a total land area of more than 18,000 square kilometres (6,900 sq mi). The terrain includes a variety of reefs, atolls, small islands, and a variety of topographical and edaphic regions on the largest island, all of which promote the development of unusually concentrated biodiversity. The region's climate is oceanic and tropical.
In biology, a refugium is a location which supports an isolated or relict population of a once more widespread species. This isolation (allopatry) can be due to climatic changes, geography, or human activities such as deforestation and overhunting.
The Sri Lanka montane rain forests is an ecoregion found above 1,000 m in the central highlands of Sri Lanka. Owing to their rich biodiversity, this region is considered to be a super-hotspot within endemic hotspots of global importance. These forests are cooler than lowland forests and therefore they have ideal conditions for growth of cloud forests. These forests classifications tropical sub montane forest, tropical sub-montane and tropical upper montane. Half of Sri Lanka's endemic flowering plants and 51 percent of the endemic vertebrates are restricted to these forests. More than 34 percent of Sri Lanka's endemic trees, shrubs, and herbs can only be found in this ecoregion. Twisted, stunted trees are a common sight in these forests, together with many varieties of orchids, mosses and ferns. The trees of montane rain forests grow to a height 10–15 meters, shorter than the lowland rain forest trees. These high altitude forests are the catchment area for most of Sri Lanka's major rivers.
A genetic isolate is a population of organisms that has little to no genetic mixing with other organisms of the same species due to geographic isolation or other factors that prevent reproduction. Genetic isolates form new species through an evolutionary process known as speciation. All modern species diversity is a product of genetic isolates and evolution.
Tropical ecology is the study of the relationships between the biotic and abiotic components of the tropics, or the area of the Earth that lies between the Tropic of Cancer and the Tropic of Capricorn. The tropical climate experiences hot, humid weather and rainfall year-round. While many might associate the region solely with the rainforests, the tropics are home to a wide variety of ecosystems that boast a great wealth of biodiversity, from exotic animal species to seldom-found flora. Tropical ecology began with the work of early English naturalists and eventually saw the establishment of research stations throughout the tropics devoted to exploring and documenting these exotic landscapes. The burgeoning ecological study of the tropics has led to increased conservation education and programs devoted to the climate. Tropical ecology provides a wealth of natural resources to humans, this includes contributing to the carbon cycle, with the ability to store 50% of carbon emissions as well as turnover 40% of global oxygen. However, despite the natural services provided by tropical ecology, deforestation is a threat of tropical rainforests. Any plant of interest can be exploited for commercial reasons and extraction of these specific plant species can be at a rapid rate without time for healthy regeneration. Most of the global plant biodiversity is hosted in tropical areas, however studies in this area is mostly covered by scientist from Northern countries. Inclusion of scientist from countries where rainforest is present is heavily encouraged because it extends global knowledge and research which advances scientific contributions, benefiting tropical ecology.
The Maputaland-Pondoland-Albany Hotspot (MPA) is a biodiversity hotspot, a biogeographic region with significant levels of biodiversity, in Southern Africa. It is situated near the south-eastern coast of Africa, occupying an area between the Great Escarpment and the Indian Ocean. The area is named after Maputaland, Pondoland and Albany. It stretches from the Albany Centre of Plant Endemism in the Eastern Cape Province of South Africa, through the Pondoland Centre of Plant Endemism and KwaZulu-Natal Province, the eastern side of Eswatini and into southern Mozambique and Mpumalanga. The Maputaland Centre of Plant Endemism is contained in northern KwaZulu-Natal and southern Mozambique.
Paleoendemism along with neoendemism is a possible subcategory of endemism. Paleoendemism refers to species that were formerly widespread but are now restricted to a smaller area. Neoendemism refers to species that have recently arisen, such as through divergence and reproductive isolation or through hybridization and polyploidy in plants.
In biogeography and paleontology, a relict is a population or taxon of organisms that was more widespread or more diverse in the past. A relictual population is a population currently inhabiting a restricted area whose range was far wider during a previous geologic epoch. Similarly, a relictual taxon is a taxon which is the sole surviving representative of a formerly diverse group.
The Luzon rain forest is a tropical moist broadleaf forest ecoregion on the island of Luzon. Luzon is the largest island in the Philippines, and the Luzon rain forest is the most extensive rainforest ecoregion of the country. The ecoregion includes the lowlands of Luzon and neighboring islands below 1000 meters elevation. Very little of the original rainforest remains, and the status of this area is critical/endangered.
A glacial refugium is a geographic region which made possible the survival of flora and fauna during ice ages and allowed for post-glacial re-colonization. Different types of glacial refugia can be distinguished, namely nunatak, peripheral, and lowland. Glacial refugia have been suggested as a major cause of floral and faunal distribution patterns in both temperate and tropical latitudes. With respect to disjunct populations of modern-day species, especially in birds, doubt has been cast on the validity of such inferences, as much of the differentiation between populations observed today may have occurred before or after their restriction to refugia. In contrast, isolated geographic locales that host one or more critically endangered species are generally uncontested as bona fide glacial refugia.
Neoendemism is one of two sub-categories of endemism, the ecological state of a species being unique to a defined geographic location. Specifically, neoendemic species are those that have recently arisen, through divergence and reproductive isolation or through hybridization and polyploidy in plants. Paleoendemism, the other sub-category, refers to species that were formerly widespread but are now restricted to a smaller area.
The vegetation in Tasmania's alpine environments is predominately woody and shrub-like. One vegetation type is coniferous shrubbery, characterised by the gymnosperm species Microcachrys tetragona, Pherosphaera hookeriana, Podocarpus lawrencei, and Diselma archeri. Distribution of these species is relevant with abiotic factors including edaphic conditions and fire frequency, and increasingly, the threat of climate change towards species survival exists. Conservation and management of coniferous shrubbery are necessary considering that the paleoendemic species, Microcachrys,Pherosphaera and Diselma, have persisted in western Tasmanian environments for millions of years.
A glacial relict is a population of a species previously common during a glacial period that retreated into refugia during interglacial periods. They are typically cold-adapted species with a distribution restricted to regions and microhabitats that allow them to survive despite climatic changes.
The Biodiversity of South Africa is the variety of living organisms within the boundaries of South Africa and its exclusive economic zone. South Africa is a region of high biodiversity in the terrestrial and marine realms. The country is ranked sixth out of the world's seventeen megadiverse countries, and is rated among the top 10 for plant species diversity and third for marine endemism.
I use the word precinctive in the sense of 'confined to the area under discussion' ... 'precinctive forms' means those forms that are confined to the area specified.