See also
- Cladogenesis
- Anagenesis, also known as "phyletic change", where no branching event occurred (or is known to have occurred)
A paraspecies (a paraphyletic species) is a species, living or fossil, that gave rise to one or more daughter species without itself becoming extinct. [1] Geographically widespread species that have given rise to one or more daughter species as peripheral isolates without themselves becoming extinct (i.e. through peripatric speciation) are examples of paraspecies. [2]
Paraspecies are expected from evolutionary theory (Crisp and Chandler, 1996), and are empirical realities in many terrestrial and aquatic taxa. [3] [4] [5] [6] [7] [8] [9] [10] [11] [12]
The polar bear is a large bear native to the Arctic and nearby areas. It is closely related to the brown bear, and the two species can interbreed. The polar bear is the largest extant species of bear and land carnivore, with adult males weighing 300–800 kg (660–1,760 lb). The species is sexually dimorphic, as adult females are much smaller. The polar bear is white- or yellowish-furred with black skin and a thick layer of fat. It is more slender than the brown bear, with a narrower skull, longer neck and lower shoulder hump. Its teeth are sharper and more adapted to cutting meat. The paws are large and allow the bear to walk on ice and paddle in the water.
Paraphyly is a taxonomic term describing a grouping that consists of the grouping's last common ancestor and some but not all of its descendant lineages. The grouping is said to be paraphyletic with respect to the excluded subgroups. In contrast, a monophyletic grouping includes a common ancestor and all of its descendants.
The tuatara is a species of reptile endemic to New Zealand. Despite its close resemblance to lizards, it is part of a distinct lineage, the order Rhynchocephalia. The name tuatara is derived from the Māori language and means "peaks on the back".
Cichlids are fish from the family Cichlidae in the order Cichliformes. Traditionally Cichlids were classed in a suborder, the Labroidei, along with the wrasses (Labridae), in the order Perciformes, but molecular studies have contradicted this grouping. On the basis of fossil evidence, it first appeared in Argentina during the Early Eocene epoch, about 48.6 million years ago; however, molecular clock estimates have placed the family's origin as far back as 67 million years ago, during the late Cretaceous period. The closest living relative of cichlids is probably the convict blenny, and both families are classified in the 5th edition of Fishes of the World as the two families in the Cichliformes, part of the subseries Ovalentaria. This family is large, diverse, and widely dispersed. At least 1,650 species have been scientifically described, making it one of the largest vertebrate families. New species are discovered annually, and many species remain undescribed. The actual number of species is therefore unknown, with estimates varying between 2,000 and 3,000.
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 Lepidosauria is a subclass or superorder of reptiles, containing the orders Squamata and Rhynchocephalia. Squamata includes lizards and snakes. Squamata contains over 9,000 species, making it by far the most species-rich and diverse order of non-avian reptiles in the present day. Rhynchocephalia was a formerly widespread and diverse group of reptiles in the Mesozoic Era. However, it is represented by only one living species: the tuatara, a superficially lizard-like reptile native to New Zealand.
The genus Catharus is an evolutionary clade of forest-dwelling passerine birds in the family Turdidae (thrushes), commonly known as nightingale-thrushes. The extant species are widely distributed across the Americas and are descended from a common ancestor that lived 4–6 million years ago. Most of the species are shy of humans, seldom leaving the cover of dense forest vegetation, where their activities are hidden from view. Thus, many fundamental aspects of their biology and life histories are poorly known.
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 living fossil is an extant taxon that phenotypically resembles related species known only from the fossil record. To be considered a living fossil, the fossil species must be old relative to the time of origin of the extant clade. Living fossils commonly are of species-poor lineages, but they need not be. While the body plan of a living fossil remains superficially similar, it is never the same species as the remote relatives it resembles, because genetic drift would inevitably change its chromosomal structure.
In evolutionary biology, sympatric speciation is the evolution of a new species from a surviving ancestral species while both continue to inhabit the same geographic region. In evolutionary biology and biogeography, sympatric and sympatry are terms referring to organisms whose ranges overlap so that they occur together at least in some places. If these organisms are closely related, such a distribution may be the result of sympatric speciation. Etymologically, sympatry is derived from Greek συν (sun-) 'together' and πατρίς (patrís) 'fatherland'. The term was coined by Edward Bagnall Poulton in 1904, who explains the derivation.
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.
Rhynchocephalia is an order of lizard-like reptiles that includes only one living species, the tuatara of New Zealand. Despite its current lack of diversity, during the Mesozoic rhynchocephalians were a speciose group with high morphological and ecological diversity. The oldest record of the group is dated to the Middle Triassic around 238 to 240 million years ago, and they had achieved global distribution by the Early Jurassic. Most rhynchocephalians belong to the group Sphenodontia ('wedge-teeth'). Their closest living relatives are lizards and snakes in the order Squamata, with the two orders being grouped together in the superorder Lepidosauria.
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. 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. An endemic species can also be referred to as an endemism or, in scientific literature, as an endemite. Similarly many species found in the Western ghats of India are examples of endemism.
Sphenodontidae is a family within the reptile group Rhynchocephalia, comprising taxa most closely related to the living tuatara. Historically the taxa included within Sphenodontidae have varied greatly between analyses, and the group has lacked a formal definition. Cynosphenodon from the Jurassic of Mexico has consistently been recovered as a close relative of the tuatara in most analyses, with the clade containing the two and other very close relatives of the tuatara often called Sphenodontinae. The herbivorous Eilenodontinae, otherwise considered part of Opisthodontia, is considered to be part of this family in many recent studies as the sister group to Sphenodontinae. The earliest Sphenodontines are known from the Early Jurassic of North America, with other remains known from the Late Jurassic of Europe, the Late Cretaceous and possibly Paleocene of South America and the Miocene-recent of New Zealand. Sphenodontines are characterised by a complete lower temporal bar caused by the fusion of a forward directed process (extension) of the quadrate/quadratojugal and the jugal, which was an adaptation for reducing stress in the skull during hard biting. Other synapomorphies of Sphenodontinae include the presence of nasal foramina, a posterodorsal process of the coronoid of the lower jaw, the present of caniniform successional teeth at the front of the jaws, the presence of flanges on the posterior parts of teeth at back of the lower jaw, and an expanded radial condyle on the humerus. Like modern tuatara, members of Sphenodontinae were likely generalists with a carnivorous/insectivorous diet.
Evidence of common descent of living organisms has been discovered by scientists researching in a variety of disciplines over many decades, demonstrating that all life on Earth comes from a single ancestor. This forms an important part of the evidence on which evolutionary theory rests, demonstrates that evolution does occur, and illustrates the processes that created Earth's biodiversity. It supports the modern evolutionary synthesis—the current scientific theory that explains how and why life changes over time. Evolutionary biologists document evidence of common descent, all the way back to the last universal common ancestor, by developing testable predictions, testing hypotheses, and constructing theories that illustrate and describe its causes.
Hybrid speciation is a form of speciation where hybridization between two different species leads to a new species, reproductively isolated from the parent species. Previously, reproductive isolation between two species and their parents was thought to be particularly difficult to achieve, and thus hybrid species were thought to be very rare. With DNA analysis becoming more accessible in the 1990s, hybrid speciation has been shown to be a somewhat common phenomenon, particularly in plants. In botanical nomenclature, a hybrid species is also called a nothospecies. Hybrid species are by their nature polyphyletic.
The Chaco sparrow, formerly known as the stripe-capped sparrow, is a species of bird in the family Passerellidae. It is found in Argentina and Paraguay.
Pronophilina is a Neotropical subtribe of butterflies of the subfamily Satyrinae. They are a species-rich group with highest diversity in the tropical and subtropical mountains, especially the Andes. Before 1970, they were poorly studied, but recent interest has resulted in high rates of species description from previously unexplored mountain ranges. However, there is still a lack of knowledge on their biology and ecology. Their relationship to other groups of Satyrine butterflies and their complex patterns of speciation within and among mountain ranges have led to several biogeographic discussions.
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.
Emberizoidea is a superfamily of passerines that are referred to as the New World nine-primaried oscines that includes majority of endemics which are exclusive to the New World. Nearly 892 species belong to this group as it includes buntings, American sparrows, the New World blackbirds, the parulid warblers, the cardinals, and the tanagers.