Hybrid (biology) in the context of Quercus

A species (pl. species) is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. It can be defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, morphology, behaviour, or ecological niche. In addition, palaeontologists use the concept of the chronospecies since fossil reproduction cannot be examined. The most recent rigorous estimate for the total number of species of eukaryotes is between 8 and 8.7 million. About 14% of these had been described by 2011. All species (except viruses) are given a two-part name, a "binomen". The first part of a binomen is the name of a genus to which the species belongs. The second part is called the specific name or the specific epithet (in botanical nomenclature, also sometimes in zoological nomenclature). For example, Boa constrictor is one of the species of the genus Boa, with constrictor being the specific name.

While the definitions given above may seem adequate at first glance, when looked at more closely they represent problematic species concepts. For example, the boundaries between closely related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, and in a ring species. Also, among organisms that reproduce only asexually, the concept of a reproductive species breaks down, and each clonal lineage is potentially a microspecies. Although none of these are entirely satisfactory definitions, and while the concept of species may not be a perfect model of life, it is still a useful tool to scientists and conservationists for studying life on Earth, regardless of the theoretical difficulties. If species were fixed and distinct from one another, there would be no problem, but evolutionary processes cause species to change. This obliges taxonomists to decide, for example, when enough change has occurred to declare that a fossil lineage should be divided into multiple chronospecies, or when populations have diverged to have enough distinct character states to be described as cladistic species.

In biology, a ring species is a connected series of neighbouring populations, each of which interbreeds with closely sited related populations, but for which there exist at least two end populations in the series which are too distantly related to interbreed, though there is a potential gene flow between linked neighbouring populations. Such non-breeding, though genetically connected, end populations may co-exist in the same region (sympatry) thus closing a ring. The German term Rassenkreis, meaning "circle of races", is also used.

Ring species represent speciation and have been cited as evidence of evolution. They illustrate what happens over time as populations genetically diverge, specifically because they represent, in living populations, what normally happens over time between long-deceased ancestor populations and living populations, in which the intermediates have become extinct. The evolutionary biologist Richard Dawkins remarks that ring species "are only showing us in the spatial dimension something that must always happen in the time dimension".

A rose is either a woody perennial flowering plant of the genus Rosa (/ˈroʊzə/), in the family Rosaceae (/roʊˈzeɪsiːˌiː/), or the flower it bears. There are over three hundred species and tens of thousands of cultivars. They form a group of plants that can be erect shrubs, climbing, or trailing, with stems that are often armed with sharp prickles. Their flowers vary in size and shape and are usually large and showy, in colours ranging from white through pinks, reds, oranges and yellows. Most species are native to Asia, with smaller numbers native to Europe, North America, and Northwest Africa. Species, cultivars and hybrids are all widely grown for their beauty and often are fragrant. Roses have acquired cultural significance in many societies. Rose plants range in size from compact, miniature roses to climbers that can reach seven meters in height. Different species hybridize easily, and this has been used in the development of the wide range of garden roses.

Camellia (pronounced /kə.ˈmɛ.li.ə/ or /kə.ˈmiː.li.ə/) is a genus of flowering plants in the family Theaceae. They are found in tropical and subtropical areas in eastern and southern Asia, from the Himalayas east to Japan and Indonesia. There are more than 220 described species; almost all are found in southern China and Indochina. Camellias are popular ornamental, tea, and woody-oil plants cultivated worldwide for centuries. Over 26,000 cultivars, with more than 51,000 cultivar names, including synonyms, have been registered or published.

The leaves of C. sinensis are processed to create tea, and so are of particular economic importance in East Asia, Southeast Asia, and the Indian subcontinent, with the processed leaves widely sold and consumed globally. The ornamental C. japonica, C. sasanqua and their hybrids are the source of hundreds of garden cultivars. C. oleifera produces tea seed oil, used in cooking and cosmetics.

Selective breeding (also called artificial selection) is the process by which humans use animal breeding and plant breeding to selectively develop particular phenotypic traits (characteristics) by choosing which typically animal or plant males and females will sexually reproduce and have offspring together. Domesticated animals are known as breeds, normally bred by a professional breeder, while domesticated plants are known as varieties, cultigens, cultivars, or breeds. Two purebred animals of different breeds produce a crossbreed, and crossbred plants are called hybrids. Flowers, vegetables and fruit-trees may be bred by amateurs and commercial or non-commercial professionals: major crops are usually the provenance of the professionals.

In animal breeding artificial selection is often combined with techniques such as inbreeding, linebreeding, and outcrossing. In plant breeding, similar methods are used. Charles Darwin discussed how selective breeding had been successful in producing change over time in his 1859 book, On the Origin of Species. Its first chapter discusses selective breeding and domestication of such animals as pigeons, cats, cattle, and dogs. Darwin used artificial selection as an analogy to propose and explain the theory of natural selection but distinguished the latter from the former as a separate process that is non-directed.

In molecular biology, complementarity describes a relationship between two structures each following the lock-and-key principle. In nature complementarity is the base principle of DNA replication and transcription as it is a property shared between two DNA or RNA sequences, such that when they are aligned antiparallel to each other, the nucleotide bases at each position in the sequences will be complementary, much like looking in the mirror and seeing the reverse of things. This complementary base pairing allows cells to copy information from one generation to another and even find and repair damage to the information stored in the sequences.

The degree of complementarity between two nucleic acid strands may vary, from complete complementarity (each nucleotide is across from its opposite) to no complementarity (each nucleotide is not across from its opposite) and determines the stability of the sequences to be together. Furthermore, various DNA repair functions as well as regulatory functions are based on base pair complementarity. In biotechnology, the principle of base pair complementarity allows the generation of DNA hybrids between RNA and DNA, and opens the door to modern tools such as cDNA libraries.While most complementarity is seen between two separate strings of DNA or RNA, it is also possible for a sequence to have internal complementarity resulting in the sequence binding to itself in a folded configuration.

Triticale (/trɪtɪˈkeɪliː/; × Triticosecale) is a hybrid of wheat (Triticum) and rye (Secale) first bred in laboratories during the late 19th century in Scotland and Germany. Commercially available triticale is almost always a second-generation hybrid, i.e., a cross between two kinds of primary (first-cross) triticales. As a rule, triticale combines the yield potential and grain quality of wheat with the disease and environmental tolerance (including soil conditions) of rye. Only in 1970 did the first commercial variety become available. Depending on the cultivar, triticale can more or less resemble either of its parents. It is grown mostly for forage or fodder, although some triticale-based foods can be purchased at health food stores and can be found in some breakfast cereals.

When crossing wheat and rye, wheat is used as the female parent and rye as the male parent (pollen donor). The resulting hybrid is sterile and must be treated with colchicine to induce polyploidy and thus the ability to reproduce itself.

Pollination is the transfer of pollen from an anther of a plant to the stigma of a plant, later enabling fertilisation and the production of seeds. Pollinating agents can be animals such as insects, for example bees, beetles or butterflies; birds, and bats; water; wind; and even plants themselves. Pollinating animals travel from plant to plant carrying pollen on their bodies in a vital interaction that allows the transfer of genetic material critical to the reproductive system of most flowering plants. Self-pollination occurs within a closed flower. Pollination often occurs within a species. When pollination occurs between species, it can produce hybrid offspring in nature and in plant breeding work.

In angiosperms, after the pollen grain (gametophyte) has landed on the stigma, it germinates and develops a pollen tube which grows down the style until it reaches an ovary. Its two gametes travel down the tube to where the gametophyte(s) containing the female gametes are held within the carpel. After entering an ovule through the micropyle, one male nucleus fuses with the polar bodies to produce the endosperm tissues, while the other fuses with the egg cell to produce the embryo. Hence the term: "double fertilisation". This process would result in the production of a seed, made of both nutritious tissues and embryo.

Genetic admixture occurs when previously isolated populations of organisms interbreed, resulting in a population with genetic ancestry from both sources. It can occur between species, such as with hybrids, or within species, such as when geographically distant individuals migrate to new regions. It results in a population with genetic backgrounds, or a gene pool, that is a mix of the source populations. Genetic admixture is recognized as an important contributor to rapid evolutionary responses, both at the level of gene flow between populations and between species.

An oak is a hardwood tree or shrub in the genus Quercus of the beech family. They have spirally arranged leaves, often with lobed edges, and a nut called an acorn, borne within a cup. The genus is widely distributed in the Northern Hemisphere, with some 500 species, both deciduous and evergreen. Fossil oaks date back to the Middle Eocene. Molecular phylogeny shows that the genus is divided into Old World and New World clades, but many oak species hybridise freely, making the genus's history difficult to resolve.

Ecologically, oaks are keystone species in habitats from Mediterranean semi-desert to subtropical rainforest. They live in association with many kinds of fungi including truffles. Oaks support more than 950 species of caterpillar, many kinds of gall wasp which form distinctive galls (roundish woody lumps such as the oak apple), and a large number of pests and diseases. Oak leaves and acorns contain enough tannin to be toxic to cattle, but pigs are able to digest them safely. Oak timber is strong and hard, and has found many uses in construction and furniture-making. The bark was traditionally used for tanning leather. Wine barrels are made of oak; these are used for aging alcoholic beverages such as sherry and whisky, giving them a range of flavours, colours, and aromas. The spongy bark of the cork oak is used to make traditional wine bottle corks. Almost a third of oak species are threatened with extinction due to climate change, invasive pests, and habitat loss.

The mule is a domestic equine hybrid between a donkey and a horse. It is the offspring of a male donkey (a jack) and a female horse (a mare). The horse and the donkey are different species, with different numbers of chromosomes; of the two possible first-generation hybrids between them, the mule is easier to obtain and more common than the hinny, which is the offspring of a male horse (a stallion) and a female donkey (a jenny).

Mules vary widely in size, and may be of any color seen in horses or donkeys. They are more patient, hardier and longer-lived than horses, and are perceived as less obstinate and more intelligent than donkeys.

Mentha, also known as mint (from Greek μίνθα míntha, Linear B mi-ta), is a genus of flowering plants in the mint family, Lamiaceae. It is estimated that 13 to 24 species exist, but the exact distinction between species is unclear. Hybridization occurs naturally where some species' ranges overlap. Many hybrids and cultivars are known.

The genus has a subcosmopolitan distribution, growing best in wet environments and moist soils.

Basil (Ocimum basilicum), also called great basil, is a culinary herb of the family Lamiaceae (mints). It is a tender plant, and is used in cuisines worldwide. In Western cuisine, the generic term "basil" refers to the variety also known as Genovese basil or sweet basil. Basil is native to tropical regions from Central Africa to Southeast Asia. In temperate climates basil is treated as an annual plant, but it can be grown as a short-lived perennial or biennial in warmer horticultural zones with tropical or Mediterranean climates.

There are many varieties of basil including sweet basil, Thai basil (O. basilicum var. thyrsiflora), and Mrs. Burns' Lemon (O. basilicum var. citriodora). O. basilicum can cross-pollinate with other species of the Ocimum genus, producing hybrids such as lemon basil (O. × citriodorum) and African blue basil (O. × kilimandscharicum).

Rubus is a large and diverse genus of flowering plants in the rose family, Rosaceae, subfamily Rosoideae, most commonly known as brambles. Fruits of various species are known as raspberries, blackberries, dewberries, and bristleberries. It is a diverse genus, with the estimated number of Rubus species varying from 250 to over 1000, found across all continents except Antarctica.

Most of these plants have woody stems with prickles like roses; spines, bristles, and gland-tipped hairs are also common in the genus. The Rubus fruit, sometimes called a bramble fruit, is an aggregate of drupelets. The term cane fruit or cane berry applies to any Rubus species or hybrid which is commonly grown with supports such as wires or canes, including raspberries, blackberries, and hybrids such as loganberry, boysenberry, marionberry and tayberry. The stems of such plants are also referred to as canes.

The polar bear (Ursus maritimus) 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 by body mass, 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.

Polar bears are both terrestrial and pagophilic (ice-living) and are considered marine mammals because of their dependence on marine ecosystems. They prefer the annual sea ice but live on land when the ice melts in the summer. They are mostly carnivorous and specialized for preying on seals, particularly ringed seals. Such prey is typically taken by ambush; the bear may stalk its prey on the ice or in the water, but also will stay at a breathing hole or ice edge to wait for prey to swim by. The bear primarily feeds on the seal's energy-rich blubber. Other prey include walruses, beluga whales and some terrestrial animals. Polar bears are usually solitary but can be found in groups when on land. During the breeding season, male bears guard females and defend them from rivals. Mothers give birth to cubs in maternity dens during the winter. Young stay with their mother for up to two and a half years.

The guinea pig or domestic guinea pig (Cavia porcellus), also known as the cavy or domestic cavy (/ˈkeɪvi/ KAY-vee), is a species of rodent belonging to the genus Cavia, family Caviidae. Breeders tend to use the name "cavy" for the animal, but "guinea pig" is more commonly used in scientific and laboratory contexts. Despite their name, guinea pigs are not native to Guinea, nor are they closely related to pigs. Instead, they originated in the Andes region of South America, where wild guinea pigs can still be found today. Studies based on biochemistry and DNA hybridization suggest they are domesticated animals that do not exist naturally in the wild, but are descendants of a closely related cavy species such as C. tschudii. Originally, they were domesticated as livestock (source of meat) in the Andean region and are still consumed in some parts of the world.

In Western society, the guinea pig has enjoyed widespread popularity as a pet since its introduction to Europe and North America by European traders in the 16th century. Their docile nature, friendly responsiveness to handling and feeding, and the relative ease of caring for them have continued to make guinea pigs a popular choice of household pets. Consequently, organizations devoted to the competitive breeding of guinea pigs have been formed worldwide. Through artificial selection, many specialized breeds with varying coat colors and textures have been selected by breeders.

The hooded crow (Corvus cornix), also colloquially called just hoodie, is a Eurasian bird species in the genus Corvus. Widely distributed, it is found across Northern, Eastern, and Southeastern Europe, as well as parts of the Middle East. It is an ashy grey bird with black head, throat, wings, tail, and thigh feathers, as well as a black bill, eyes, and feet. Like other corvids, it is an omnivorous and opportunistic forager and feeder.

The hooded crow is so similar in morphology and habits to the carrion crow (Corvus corone) that for many years they were considered by most authorities to be geographical subcategories of one species. Extensive but geographically restricted hybridisation observed where their ranges met added weight to this view. However, since 2002, the hooded crow has been elevated to full species status after closer observation; the hybridisation was less than expected and hybrids had decreased vigour. Within the species, four subspecies are accepted.

The grapefruit (Citrus × paradisi) is a subtropical citrus tree known for its relatively large, sour to semi-sweet, somewhat bitter fruit. The flesh of the fruit is segmented and varies in color from pale yellow to dark red.

Grapefruits originated in Barbados in the 18th century. They are a citrus hybrid that was created through an accidental cross between the sweet orange (C. × sinensis) and the pomelo (C. maxima), both of which were introduced to the Caribbean from Asia in the 17th century. It has also been called the 'forbidden fruit'. In the past it was called the pomelo, but that term is now mostly used as the common name for Citrus maxima.