In biology, a taxon with a disjunct distribution is one that has two or more groups that are related but considerably separated from each other geographically. The causes are varied and might demonstrate either the expansion or contraction of a species' range. [1]
Also called range fragmentation, disjunct distributions may be caused by changes in the environment, such as mountain building and continental drift or rising sea levels; it may also be due to an organism expanding its range into new areas, by such means as rafting, or other animals transporting an organism to a new location (plant seeds consumed by birds and animals can be moved to new locations during bird or animal migrations, and those seeds can be deposited in new locations in fecal matter). Other conditions that can produce disjunct distributions include: flooding, or changes in wind, stream, and current flows, plus others such as anthropogenic introduction of alien introduced species either accidentally or deliberately (agriculture and horticulture).
Disjunct distributions can occur when suitable habitat is fragmented, which produces fragmented populations, and when that fragmentation becomes so divergent that species movement between one suitable habitat to the next is disrupted, isolated population can be produced. Extinctions can cause disjunct distribution, especially in areas where only scattered areas are habitable by a species; [2] for instance, island chains or specific elevations along a mountain range or areas along a coast or between bodies of water like streams, lakes and ponds. [3]
There are many patterns of disjunct distributions at many scales: Irano-Turanian disjunction, Europe - East Asia, Europe-South Africa (e.g. genus Erica ), Mediterranean-Hoggart disjunction (genus Olea ), etc.
This kind of disjunct distribution of a species, such that it occurs in Iberia and in Ireland, without any intermediate localities, is usually called "Lusitanian" (named after the Roman Province Lusitania, corresponding roughly to modern-day Portugal).
Examples of animal species with a Lusitanian distribution are: the Kerry slug Geomalacus maculosus and the Pyrenean glass snail Semilimax pyrenaicus . Plant species with this kind of distribution include several heather species (Calluna spp.) and the strawberry tree (Arbutus unedo).
The theory behind the name "Lusitanian" is now discredited; it posited that there was an ice-free land mass that served as a refugium off of the south-west of Ireland during the Quaternary (last) glaciation. In this refugium, relic fauna and flora from a previous ice-free period survived until the present warmer interstadial period. Although the theory is no longer accepted, the term Lusitanian is still used as a descriptive term for faunal elements such as the Kerry slug.
Recently a better explanation of the occurrence of the Kerry slug and similar faunal elements in southwestern Ireland has been developed. This new theory is supported by two recent discoveries: the genetic similarity of much of Ireland's fauna to that of northern Spain, and the genetic similarity of much of Ireland's human population to that of northern Spain.
Mascheretti et al. (2003) [4] examined the genotypes of Eurasian pygmy shrew, a small mammal, across its range in Europe. The Irish population showed close genetic affinity to a population from Andorra but not to that of Britain or other places in Europe. The genetic structure of the population further showed that the entire Irish population of the Eurasian pygmy shrew had originated from a single founder event. The authors concluded that it had been introduced in the early (Paleolithic) or middle (Mesolithic) Stone Age, by boat, probably from south-west Europe. This coincides with work on human populations, which found [5] [6] a strong genetic similarity in make-up between populations in western Ireland and in northern Spain. This would be explained by a human migration from Spain to Ireland in the late Paleolithic or early Mesolithic.
It seems increasingly likely that much of Ireland's Lusitanian fauna is in reality an artefact of this era of human expansion in the early part of the Postglacial era. In other words, it seems likely that these species were introduced accidentally with trade items or goods brought by boat from Iberia.
Biogeography is the study of the distribution of species and ecosystems in geographic space and through geological time. Organisms and biological communities often vary in a regular fashion along geographic gradients of latitude, elevation, isolation and habitat area. Phytogeography is the branch of biogeography that studies the distribution of plants. Zoogeography is the branch that studies distribution of animals. Mycogeography is the branch that studies distribution of fungi, such as mushrooms.
The mountain pygmy possum ; also simply known as the burramys, is a small, mouse-sized nocturnal marsupial of Australia found in dense alpine rock screes and boulder fields, mainly southern Victoria and around Mount Kosciuszko in Kosciuszko National Park in New South Wales at elevations from 1,300 to 2,230 metres. At almost 14 cm (5.5 in), its prehensile tail is longer than its 11 cm (4.3 in) combined head and body length. Its diet consists of insects, fleshy fruits, nuts, nectar and seeds. Its body is covered in a thick coat of fine grey fur except for its stomach, which is cream coloured; its tail is hairless. On the underside of the female's body is a pouch containing four teats. This possum is the only extant species in the genus Burramys. It is also the only Australian mammal restricted to alpine habitat.
Habitat fragmentation describes the emergence of discontinuities (fragmentation) in an organism's preferred environment (habitat), causing population fragmentation and ecosystem decay. Causes of habitat fragmentation include geological processes that slowly alter the layout of the physical environment, and human activity such as land conversion, which can alter the environment much faster and causes the extinction of many species. More specifically, habitat fragmentation is a process by which large and contiguous habitats get divided into smaller, isolated patches of habitats.
Lusitanian was an Indo-European Paleohispanic language. There has been support for either a connection with the ancient Italic languages or Celtic languages. It is known from only six sizeable inscriptions, dated from c. 1 CE, and numerous names of places (toponyms) and of gods (theonyms). The language was spoken in the territory inhabited by Lusitanian tribes, from the Douro to the Tagus rivers, territory that today falls in central Portugal and western Spain.
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 chalkhill blue is a butterfly in the family Lycaenidae. It is a small butterfly that can be found throughout the Palearctic realm, where it occurs primarily in grasslands rich in chalk. Males have a pale blue colour, while females are brown. Both have chequered fringes around their wings.
The greater white-toothed shrew is a small insectivorous mammal found in Europe and North Africa. It is the most common of the white-toothed shrews. This species is found along the Mediterranean, Netherlands, Belgium, Ireland, Germany and Portugal; in addition, the Osorio shrew of the Canary island of Gran Canaria, originally described as a separate species, was later discovered to be a population of introduced greater white-toothed shrew. Furthermore, a subspecies of the greater white-toothed shrew, Crocidura russula ibicensis, is found on the Mediterranean island of Ibiza. In April 2008, the greater white-toothed shrew was discovered in Ireland as well. Its preferred habitats are grassland and woodland. It is slightly larger than the lesser white-toothed shrew but otherwise very similar and can often be distinguished only by close inspection of its teeth which are unpigmented.
The island of Great Britain, along with the rest of the archipelago known as the British Isles, has a largely temperate climate. It contains a relatively small fraction of the world's wildlife. The biota was severely diminished in the last ice age, and shortly thereafter was separated from the continent by the English Channel's formation. Since then, humans have hunted the most dangerous forms to extinction, though domesticated forms such as the dog and the pig remain. The wild boar has subsequently been reintroduced as a meat animal.
The fauna of Europe is all the animals living in Europe and its surrounding seas and islands. Since there is no natural biogeographic boundary in the east and south between Europe and Asia, the term "fauna of Europe" is somewhat elusive. Europe is the western part of the Palearctic realm. Lying within the temperate region, the wildlife is not as rich as in the hottest regions, but is nevertheless diverse due to the variety of habitats and the faunal richness of Eurasia as a whole.
The Kerry slug or Kerry spotted slug is a species of terrestrial, pulmonate, gastropod mollusc. It is a medium-to-large sized, air-breathing land slug in the family of roundback slugs, Arionidae.
The fauna of Ireland comprises all the animal species inhabiting the island of Ireland and its surrounding waters.
The North African hedgehog or Algerian hedgehog, is a mammal species in the family Erinaceidae native to Algeria, Libya, Malta, Morocco, Spain, and Tunisia. Little is known about this hedgehog, even though the most common breed of domesticated hedgehogs is a result of crossing a four-toed hedgehog with a North African hedgehog. Because this species of hedgehog is native to Africa, it has been suggested that it was introduced by humans to the other countries where it is now found, including Spain and the Canary Islands. Of the four African hedgehog species, the North African hedgehog is the only one of these hedgehogs that occurs outside Africa. Because the North African hedgehog has such a wide habitat range and has a seemingly stable population, both in the wild and in the domesticated capacity, it does not appear to currently be at risk.
The forest shrew is a species of shrew in the mouse shrew family, Soricidae. It is found in Lesotho, South Africa, and Eswatini. Its natural habitats include temperate forests, dry savanna, Mediterranean-type shrubby vegetation, and temperate grassland. The term "forest shrews" in the plural is sometimes confusingly used to collectively refer to a different genus, Sylvisorex.
The ornate shrew is a species of mammal in the family Soricidae (shrews). It is endemic to western North America, ranging from Northern California in the United States to Baja California in Mexico. Eight subspecies are known, including the extinct tule shrew, known only from four specimens collected in 1905, and the Suisun ornate shrew, a species of conservation concern in California. Through skull morphology research and genetic testing on Ornate shrew populations, it has been shown that there are three main genetic subdivisions: The Southern, Central and Northern. These three genetic subdivisions of Ornate shrew arose from populations of Ornate shrews getting geographically isolated from other populations.
Pre-Celtic Europe is the period of the prehistory of Europe before the emergence and spread of the Celtic people.
Semilimax pyrenaicus is a species of air-breathing land snail, a terrestrial pulmonate gastropod mollusk in the family Vitrinidae. It is a large greyish-brown snail that cannot fully retract into its shell.
The fauna of England is similar to that of other areas British Isles and lies within the Palearctic realm. England's fauna is mainly made up of small animals and is notable for having few large mammals, but in similarity with other island nations; many bird species.
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.
A glacial refugium is a geographic region which made possible the survival of flora and fauna in times of ice ages and allowed for post-glacial re-colonization. Different types of glacial refugia can be distinguished, namely nunatak, peripheral and lowland refugia. Glacial refugia have been suggested as a major cause of the patterns of distributions of flora and fauna in both temperate and tropical latitudes. With respect to disjunct populations of modern-day species distributions, 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.