106-531: See text Commonly known as hellebores ( / ˈ h ɛ l ə b ɔːr z / ), the Eurasian genus Helleborus consists of approximately 20 species of herbaceous or evergreen perennial flowering plants in the family Ranunculaceae , within which it gave its name to the tribe of Helleboreae . Many hellebore species are poisonous. Despite common names such as winter rose , Christmas rose , and Lenten rose , hellebores are not closely related to
212-475: A synthetic population . In horticulture , the term stable hybrid is used to describe an annual plant that, if grown and bred in a small monoculture free of external pollen (e.g., an air-filtered greenhouse) produces offspring that are "true to type" with respect to phenotype; i.e., a true-breeding organism. Hybridization can occur in the hybrid zones where the geographical ranges of species, subspecies, or distinct genetic lineages overlap. For example,
318-463: A bactrian camel and a dromedary . There are many examples of felid hybrids , including the liger . The oldest-known animal hybrid bred by humans is the kunga equid hybrid produced as a draft animal and status symbol 4,500 years ago in Umm el-Marra , present-day Syria . The first known instance of hybrid speciation in marine mammals was discovered in 2014. The clymene dolphin ( Stenella clymene )
424-633: A hybrid is the offspring resulting from combining the qualities of two organisms of different varieties , subspecies , species or genera through sexual reproduction . Generally, it means that each cell has genetic material from two different organisms, whereas an individual where some cells are derived from a different organism is called a chimera . Hybrids are not always intermediates between their parents such as in blending inheritance (a now discredited theory in modern genetics by particulate inheritance ), but can show hybrid vigor , sometimes growing larger or taller than either parent. The concept of
530-564: A bear shot by a hunter in the Northwest Territories confirmed the existence of naturally occurring and fertile grizzly–polar bear hybrids . Hybridization between reproductively isolated species often results in hybrid offspring with lower fitness than either parental. However, hybrids are not, as might be expected, always intermediate between their parents (as if there were blending inheritance), but are sometimes stronger or perform better than either parental lineage or variety,
636-515: A considerable seed yield advantage over open pollinated varieties. Hybrid seed dominates the commercial maize seed market in the United States, Canada and many other major maize-producing countries. In a hybrid, any trait that falls outside the range of parental variation (and is thus not simply intermediate between its parents) is considered heterotic. Positive heterosis produces more robust hybrids, they might be stronger or bigger; while
742-509: A cross between a female horse and a male donkey, and the hinny, a cross between a female donkey and a male horse. Pairs of complementary types like the mule and hinny are called reciprocal hybrids. Polar bears and brown bears are another case of a hybridizing species pairs, and introgression among non-sister species of bears appears to have shaped the Ursidae family tree. Among many other mammal crosses are hybrid camels , crosses between
848-491: A darker colour, are much sought-after, as are those with dark nectaries which contrast with the outer sepals. Recent breeding programmes have also created double-flowered and anemone-centred plants. Ironically, doing this is actually reversing the evolutionary process in which hellebores' true petals had been modified into nectaries ; it is usually these nectaries which become the extra petals in double, semi-double and anemone-centred flowers. Double-flowered hellebores provide
954-509: A degree that none of the originally genetically distinct population remains. In agriculture and animal husbandry , the Green Revolution 's use of conventional hybridization increased yields by breeding high-yielding varieties . The replacement of locally indigenous breeds, compounded with unintentional cross-pollination and crossbreeding (genetic mixing), has reduced the gene pools of various wild and indigenous breeds resulting in
1060-602: A donkey as the father. A variety of mechanisms limit the success of hybridization, including the large genetic difference between most species. Barriers include morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or the developing embryo. Some act before fertilization; others after it. In plants, some barriers to hybridization include blooming period differences, different pollinator vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and structural differences of
1166-548: A group of about 50 natural hybrids between Australian blacktip shark and the larger common blacktip shark was found by Australia's eastern coast in 2012. Russian sturgeon and American paddlefish were hybridized in captivity when sperm from the paddlefish and eggs from the sturgeon were combined, unexpectedly resulting in viable offspring. This hybrid is called a sturddlefish . The two genera Asymmetron and Branchiostoma are able to produce viable hybrid offspring, even if none have lived into adulthood so far, despite
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#17327760894021272-466: A honeydew that can lead to the growth of sooty mold on the leaves and flowers of the hellebore. This species of aphid only affects hellebores and is most active in March and April when the hellebores are flowering and when few aphid predators are around, though they may infest during any time of the year. Aphids start their feeding from the outside the flowers, beginning at the leaves and then moving towards
1378-500: A hybrid is interpreted differently in animal and plant breeding, where there is interest in the individual parentage. In genetics , attention is focused on the numbers of chromosomes . In taxonomy, a key question is how closely related the parent species are. Species are reproductively isolated by strong barriers to hybridization, which include genetic and morphological differences, differing times of fertility, mating behaviors and cues, and physiological rejection of sperm cells or
1484-439: A long time, both intentionally for purposes such as biological control , and unintentionally, as with accidental escapes of individuals. Introductions can drastically affect populations, including through hybridization. There is a kind of continuum with three semi-distinct categories dealing with anthropogenic hybridization: hybridization without introgression, hybridization with widespread introgression (backcrossing with one of
1590-498: A mate among the species that raised it, instead of the species of its biological parents. Cagebird breeders sometimes breed bird hybrids known as mules between species of finch , such as goldfinch × canary . Among amphibians, Japanese giant salamanders and Chinese giant salamanders have created hybrids that threaten the survival of Japanese giant salamanders because of competition for similar resources in Japan. Among fish,
1696-502: A more efficient path to the ocean than the existing Volga–Don Canal . This usage can also be seen in the names of Eurasianet , The Journal of Eurasian Studies , and the Association for Slavic, East European, and Eurasian Studies , as well as the titles of numerous academic programmes at US universities. This usage is comparable to how Americans use " Western Hemisphere " to describe concepts and organizations dealing with
1802-432: A phenomenon called heterosis, hybrid vigour, or heterozygote advantage . This is most common with plant hybrids. A transgressive phenotype is a phenotype that displays more extreme characteristics than either of the parent lines. Plant breeders use several techniques to produce hybrids, including line breeding and the formation of complex hybrids. An economically important example is hybrid maize (corn), which provides
1908-405: A species, such as between different breeds . Single cross hybrids result from the cross between two true-breeding organisms which produces an F1 hybrid (first filial generation). The cross between two different homozygous lines produces an F1 hybrid that is heterozygous ; having two alleles , one contributed by each parent and typically one is dominant and the other recessive . Typically,
2014-517: A very interesting variation to the standard hellebore. They are generally easy to maintain and share the same planting conditions as the standard hellebore. Semi-double flowers have one or two extra rows of petals; doubles have more. Their inner petals are generally very like the outer ones in colour and patterning. They are often of a similar length and shape, though they may be slightly shorter and narrower, and some are attractively waved or ruffled. By contrast, anemone-centred flowers have, cupped within
2120-470: Is a historical social construct , as neither fits the usual definition; thus, in some parts of the world, Eurasia is recognized as the largest of the six, five, or four continents on Earth. Eurasia covers around 55 million square kilometres (21 million square miles), or around 36.2% of the Earth's total land area. The landmass contains well over 5 billion people, equating to approximately 70% of
2226-577: Is a hybrid of two Atlantic species, the spinner and striped dolphins . In 2019, scientists confirmed that a skull found 30 years earlier was a hybrid between the beluga whale and narwhal , dubbed the narluga . Hybridization between species is common in birds. Hybrid birds are purposefully bred by humans, but hybridization is also common in the wild. Waterfowl have a particularly high incidence of hybridization, with at least 60% of species known to produce hybrids with another species. Among ducks , mallards widely hybridize with many other species, and
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#17327760894022332-407: Is a hybridization test widely used in genetics to determine whether two separately isolated mutants that have the same (or similar) phenotype are defective in the same gene or in different genes (see Complementation (genetics) article). If a hybrid organism containing the genomes of two different mutant parental organisms displays a wild type phenotype, it is ordinarily considered that
2438-571: Is a particularly common mechanism for speciation in plants, and is now known to be fundamental to the evolutionary history of plants. Plants frequently form polyploids , individuals with more than two copies of each chromosome. Whole genome doubling has occurred repeatedly in plant evolution. When two plant species hybridize, the hybrid may double its chromosome count by incorporating the entire nuclear genome of both parents, resulting in offspring that are reproductively incompatible with either parent because of different chromosome counts. Human impact on
2544-659: Is also more occasionally done in the livestock and pet trades; some well-known wild × domestic hybrids are beefalo and wolfdogs . Human selective breeding of domesticated animals and plants has also resulted in the development of distinct breeds (usually called cultivars in reference to plants); crossbreeds between them (without any wild stock ) are sometimes also imprecisely referred to as "hybrids". Hybrid humans existed in prehistory. For example, Neanderthals and anatomically modern humans are thought to have interbred as recently as 40,000 years ago. Mythological hybrids appear in human culture in forms as diverse as
2650-451: Is always sterile worker ants (and because ants are haplodiploid , unfertilized eggs become males). Without mating with males of the other species, the queens are unable to produce workers, and will fail to establish a colony of their own. Plant species hybridize more readily than animal species, and the resulting hybrids are fertile more often. Many plant species are the result of hybridization, combined with polyploidy , which duplicates
2756-537: Is becoming popular, as are more recent selections with golden-yellow foliage. Eurasia Eurasia ( / j ʊəˈr eɪ ʒ ə / yoor- AY -zhə , also UK : /- ʃ ə / -shə ) is the largest continental area on Earth, comprising all of Europe and Asia . According to some geographers, physiographically , Eurasia is a single supercontinent . The concepts of Europe and Asia as distinct continents date back to antiquity , but their borders have historically been subject to change. For example, to
2862-552: Is derived from Latin hybrida , used for crosses such as of a tame sow and a wild boar. The term came into popular use in English in the 19th century, though examples of its use have been found from the early 17th century. Conspicuous hybrids are popularly named with portmanteau words , starting in the 1920s with the breeding of tiger–lion hybrids ( liger and tigon ). From the point of view of animal and plant breeders, there are several kinds of hybrid formed from crosses within
2968-471: Is disputed, since Mount Elbrus would be part of Europe in the latter case, making it (and not Mont Blanc ) Europe's highest mountain. Most accepted is probably the boundary as defined by Philip Johan von Strahlenberg in the 18th century. He defined the dividing line along the Aegean Sea , Dardanelles , Sea of Marmara , Bosporus , Black Sea , Kuma–Manych Depression , Caspian Sea , Ural River , and
3074-412: Is not recommended to spray flowering hellebores as it may harm the non-aphid pollinating insects. Botrytis cinerea or grey mold is a fungal disease that infects most ornamental plants. The fungus causes a decay of plant tissues and grows fuzzy gray-brown mold over the decaying areas, such as the buds, leaves, and flowers. Parts of the plant may shrivel and die after exposure to the mold, particularly
3180-527: Is often used in Kazakhstan to describe its location. Numerous Kazakh institutions have the term in their names, like the L. N. Gumilev Eurasian National University ( Kazakh : Л. Н. Гумилёв атындағы Еуразия Ұлттық университеті ; Евразийский Национальный университет имени Л. Н. Гумилёва ) ( Lev Gumilev 's Eurasianism ideas having been popularized in Kazakhstan by Olzhas Suleimenov ),
3286-427: Is that hybrid individuals can form a "bridge" transmitting potentially helpful genes from one species to another when the hybrid backcrosses with one of its parent species, a process called introgression . Hybrids can also cause speciation , either because the hybrids are genetically incompatible with their parents and not each other, or because the hybrids occupy a different niche than either parent. Hybridization
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3392-515: Is the proper time to give up on a population that is becoming a hybrid swarm, or to try and save the still existing pure individuals. Once a population becomes a complete mixture, the goal becomes to conserve those hybrids to avoid their loss. Conservationists treat each case on its merits, depending on detecting hybrids within the population. It is nearly impossible to formulate a uniform hybridization policy, because hybridization can occur beneficially when it occurs "naturally", and when hybrid swarms are
3498-460: Is to reduce the humidity around the plant by improving the ventilation and ensuring the plants are not overcrowded. Coniothyrium hellebori is a fungus that causes the most common fungal disease for helleborus species known as Hellebore black spot or leaf spot . The disease is most common not only in botanical and ornamental gardens but also in hellebore nurseries as well. Visible symptoms include blackish-brown spots that often appear as rings on
3604-1060: The Alps , the Arctic, the Pacific, the Atlantic, the Mediterranean, the Black Sea and the Caspian Sea, a definition that has been influential in Russia and other parts of the former Soviet Union. Nowadays, partly inspired by this usage, the term Eurasia is sometimes used to refer to the post-Soviet space – in particular Russia, the Central Asian republics, and the Transcaucasus republics – and sometimes also adjacent regions such as Turkey and Mongolia . The word "Eurasia"
3710-564: The Anglo-Latin word elleborus had varied meanings. Around 900 AD, it was linked with " tunsingwyrt " (various spellings; likely an allium such as wild garlic ) in the Old English Herbarium . Ælfric of Eynsham seemed to assert that elleborus had no vernacular Old English translation; by the early 11th century, " wodewistle " was used to gloss the word, possibly referring to hemlock or similar. These shifts reflect
3816-716: The Greeks classified Europe (derived from the mythological Phoenician princess Europa ) and Asia which to the Greeks originally included Africa (derived from Asia , a woman in Greek mythology ) as separate "lands". Where to draw the dividing line between the two regions is still a matter of discussion . Especially whether the Kuma-Manych Depression or the Caucasus Mountains form the southeast boundary
3922-514: The Hellebore leaf miner , Phytomyza hellebori is a small fly that infests only the H. foetidus plants in the Hellebore genus. The leaf miner fly digs tunnels into the leaves of the H. foetidus. The tunnels create brownish-black blotches on the plant. These later turn into a nesting ground where the flies lay their eggs. With time, the leaves turn a brownish-white along where
4028-650: The Köppen classification , including the harshest types of hot and cold temperatures, high and low precipitation, and various types of ecosystems . Eurasia is considered a supercontinent , part of the supercontinent of Afro-Eurasia or simply a continent in its own right. In plate tectonics , the Eurasian Plate includes Europe and most of Asia but not the Indian subcontinent, the Arabian Peninsula or
4134-653: The Minotaur , blends of animals, humans and mythical beasts such as centaurs and sphinxes , and the Nephilim of the Biblical apocrypha described as the wicked sons of fallen angels and attractive women. Hybridization between species plays an important role in evolution, though there is much debate about its significance. Roughly 25% of plants and 10% of animals are known to form hybrids with at least one other species. One example of an adaptive benefit to hybridization
4240-587: The Royal Horticultural Society 's Award of Garden Merit : Various species of this genus originated in Europe and Asia . The greatest concentration of species occurs in the Balkans . One atypical species ( H. thibetanus ) comes from western China ; another atypical species ( H. vesicarius ) inhabits a small area on the border between Turkey and Syria . More commonly known as
4346-789: The Russian Far North to Maritime Southeast Asia in the south, but other specific geographical limits of Eurasia states that the southern limit is in the Weber's line . Eurasia is bordered by Africa to the southwest, the Atlantic Ocean to the west, the Arctic Ocean to the north, the Pacific Ocean to the east, and the Indo-Mediterranean to the south. The division between Europe and Asia as two continents
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4452-549: The Soviet Union ) then dominated much of the continent until the end of the Cold War in 1991. Originally, "Eurasia" is a geographical notion: in this sense, it is simply the biggest continent; the combined landmass of Europe and Asia. However, geopolitically, the word has several meanings, reflecting specific geopolitical interests. "Eurasia" is one of the most important geopolitical concepts and it figures prominently in
4558-1240: The Transhimalaya . Other high ranges include the Kunlun , Hindu Raj , and Caucasus Mountains . The Alpide belt stretches 15,000 km across southern Eurasia, from Java in Maritime Southeast Asia to the Iberian Peninsula in Western Europe , including the ranges of the Himalayas, Karakoram, Hindu Kush, Alborz , Caucasus, and the Alps . Long ranges outside the Alpide Belt include the East Siberian , Altai , Scandinavian , Qinling , Western Ghats , Vindhya , Byrranga , and Annamite Ranges . The largest Eurasian islands by area are Borneo , Sumatra , Honshu , Great Britain, Sulawesi , Java, Luzon , Iceland, Mindanao , Ireland , Hokkaido , Sakhalin , and Sri Lanka . The five most-populated islands in
4664-584: The Ural Mountains . However, at least part of this definition has been subject to criticism by many modern analytical geographers like Halford Mackinder , who saw little validity in the Ural Mountains as a boundary between continents. Nineteenth-century Russian philosopher Nikolai Danilevsky defined Eurasia as an entity separate from Europe and Asia, bounded by the Himalayas, the Caucasus,
4770-592: The heterogeneous dispositif such metapolitical constructs used to control and exercise power. Across Eurasia, several single markets have emerged, including the Eurasian Economic Space , European Single Market , ASEAN Economic Community , and the Gulf Cooperation Council . There are also several international organizations and initiatives which seek to promote integration throughout Eurasia, including: In ancient times,
4876-610: The human population . Humans first settled in Eurasia from Africa 125,000 years ago. Eurasia contains many peninsulas, including the Arabian Peninsula , Korean Peninsula , Indian subcontinent , Anatolia Peninsula , Kamchatka Peninsula , and Europe, which itself contains peninsulas such as the Italian or Iberian Peninsula. Due to its vast size and differences in latitude , Eurasia exhibits all types of climates under
4982-472: The sea urchin Strongylocentrotus purpuratus (female) and the sand dollar Dendraster excentricus (male). When two distinct types of organisms breed with each other, the resulting hybrids typically have intermediate traits (e.g., one plant parent has red flowers, the other has white, and the hybrid, pink flowers). Commonly, hybrids also combine traits seen only separately in one parent or
5088-438: The "suture region". It is at these regions that the subspecies were formed. Other hybrid zones have formed between described species of plants and animals. From the point of view of genetics, several different kinds of hybrid can be distinguished. A genetic hybrid carries two different alleles of the same gene , where for instance one allele may code for a lighter coat colour than the other. A structural hybrid results from
5194-658: The Americas (e.g., Council on Hemispheric Affairs , Western Hemisphere Institute for Security Cooperation ). [REDACTED] Africa [REDACTED] Antarctica [REDACTED] Asia [REDACTED] Australia [REDACTED] Europe [REDACTED] North America [REDACTED] South America [REDACTED] Afro-Eurasia [REDACTED] Americas [REDACTED] Eurasia [REDACTED] Oceania 50°N 80°E / 50°N 80°E / 50; 80 Hybridization (biology) In biology ,
5300-837: The Eurasian Media Forum, the Eurasian Cultural Foundation ( Евразийский фонд культуры ), the Eurasian Development Bank ( Евразийский банк развития ), and the Eurasian Bank. In 2007 Kazakhstan's president, Nursultan Nazarbayev , proposed building a " Eurasia Canal " to connect the Caspian Sea and the Black Sea via Russia's Kuma-Manych Depression to provide Kazakhstan and other Caspian-basin countries with
5406-506: The F1 generation is also phenotypically homogeneous, producing offspring that are all similar to each other. Double cross hybrids result from the cross between two different F1 hybrids (i.e., there are four unrelated grandparents). Three-way cross hybrids result from the cross between an F1 hybrid and an inbred line. Triple cross hybrids result from the crossing of two different three-way cross hybrids. Top cross (or "topcross") hybrids result from
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#17327760894025512-612: The UK is H. orientalis , but all hellebores are susceptible to the disease. The most effective method of treatment against black death is to dig up and destroy all infected plants immediately. Many viruses are not transmitted through seeds, so it is possible to raise new disease resistant plants this way. Pseudomonas viridiflava is a bacterium that has been claimed to cause disease in hellebores in New Zealand , among other plants. The bacterial disease manifested on hellebore plants in
5618-481: The Western Hemisphere and Oceania geopolitically peripheral to the world's central continent. About 75 per cent of the world's people live in 'Eurasia', and most of the world's physical wealth is there as well, both in its enterprises and underneath its soil. 'Eurasia' accounts for about three-fourths of the world's known energy resources." The Russian " Eurasianism " corresponded initially more or less to
5724-667: The ancient Greeks , Asia originally included Africa but they classified Europe as separate land. Eurasia is connected to Africa at the Suez Canal , and the two are sometimes combined to describe the largest contiguous landmass on Earth, Afro-Eurasia . Primarily in the Northern and Eastern Hemispheres , Eurasia spans from Iceland and the Iberian Peninsula in the west to the Russian Far East , and from
5830-540: The area of the Russian Far East east of the Chersky Range . From the point of view of history and culture, Eurasia can be loosely subdivided into Western Eurasia and Eastern Eurasia . In geology, Eurasia is often considered as a single rigid megablock, but this is debated. Eurasia formed between 375 and 325 million years ago with the merging of Siberia , Kazakhstania , and Baltica , which
5936-524: The butterfly Limenitis arthemis has two major subspecies in North America, L. a. arthemis (the white admiral) and L. a. astyanax (the red-spotted purple). The white admiral has a bright, white band on its wings, while the red-spotted purple has cooler blue-green shades. Hybridization occurs between a narrow area across New England, southern Ontario, and the Great Lakes,
6042-426: The chromosomes. A few animal species are the result of hybridization. The Lonicera fly is a natural hybrid. The American red wolf appears to be a hybrid of the gray wolf and the coyote , although its taxonomic status has been a subject of controversy. The European edible frog is a semi-permanent hybrid between pool frogs and marsh frogs ; its population requires the continued presence of at least one of
6148-547: The chromosomes. Chromosome duplication allows orderly meiosis and so viable seed can be produced. Plant hybrids are generally given names that include an "×" (not in italics), such as Platanus × hispanica for the London plane, a natural hybrid of P. orientalis (oriental plane) and P. occidentalis (American sycamore). The parent's names may be kept in their entirety, as seen in Prunus persica × Prunus americana , with
6254-520: The colour-range of the flowers, which now extends from slate grey, near-black, deep purple and plum, through rich red and pinks to yellow, white and green. The outer surface of the sepals is often green-tinged, and as the flower ages it usually becomes greener inside and out; individual flowers often remain on the plant for a month or more. The inner surface of each sepal may be marked with veins, or dotted or blotched with pink, red or purple. " Picotee " flowers, whose pale-coloured sepals have narrow margins of
6360-407: The commentaries on the ideas of Halford Mackinder . As Zbigniew Brzezinski observed on Eurasia: "... how America 'manages' Eurasia is critical. A power that dominates 'Eurasia' would control two of the world's three most advanced and economically productive regions. A mere glance at the map also suggests that control over 'Eurasia' would almost automatically entail Africa's subordination, rendering
6466-481: The common pheasant and hen golden pheasant ( Chrysolophus pictus ). Spurs are absent in hybrids of the former type, although present in both parents. Hybridization is greatly influenced by human impact on the environment, through effects such as habitat fragmentation and species introductions. Such impacts make it difficult to conserve the genetics of populations undergoing introgressive hybridization . Humans have introduced species worldwide to environments for
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#17327760894026572-400: The crossing of a top quality or pure-bred male and a lower quality female, intended to improve the quality of the offspring, on average. Population hybrids result from the crossing of plants or animals in one population with those of another population. These include interspecific hybrids or crosses between different breeds. In biology, the result of crossing of two populations is called
6678-444: The developing embryo . Some act before fertilization and others after it. Similar barriers exist in plants, with differences in flowering times, pollen vectors, inhibition of pollen tube growth, somatoplastic sterility, cytoplasmic-genic male sterility and the structure of the chromosomes. A few animal species and many plant species, however, are the result of hybrid speciation , including important crop plants such as wheat , where
6784-464: The developing understanding of Latin plant names in Old English texts. The flowers have five petal-like sepals surrounding a ring of small, cup-like nectaries which are actually petals modified to hold nectar . The sepals do not fall as petals would, but remain on the plant, sometimes for many months. The persistence of the sepals may contribute to the development of the seeds . The genus
6890-407: The diverse Heliconius butterflies , but that is disputed. The two closely related harvester ant species Pogonomyrmex barbatus and Pogonomyrmex rugosus have evolved to depend on hybridization. When a queen fertilizes her eggs with sperm from males of her own species, the offspring is always new queens. And when she fertilizes the eggs with sperm from males of the other species, the offspring
6996-413: The doubling of chromosome sets, causing immediate genetic isolation. Hybridization may be important in speciation in some plant groups. However, homoploid hybrid speciation (not increasing the number of sets of chromosomes) may be rare: by 1997, only eight natural examples had been fully described. Experimental studies suggest that hybridization offers a rapid route to speciation, a prediction confirmed by
7102-611: The environment has resulted in an increase in the interbreeding between regional species, and the proliferation of introduced species worldwide has also resulted in an increase in hybridization. This has been referred to as genetic pollution out of concern that it may threaten many species with extinction. Similarly, genetic erosion from monoculture in crop plants may be damaging the gene pools of many species for future breeding. The conservation impacts of hybridization between species are highly debated. While hybridization could potentially threaten rare species or lineages by "swamping"
7208-429: The fact that early generation hybrids and ancient hybrid species have matching genomes, meaning that once hybridization has occurred, the new hybrid genome can remain stable. Many hybrid zones are known where the ranges of two species meet, and hybrids are continually produced in great numbers. These hybrid zones are useful as biological model systems for studying the mechanisms of speciation. Recently DNA analysis of
7314-555: The five normal outer petals, a ring of much shorter, more curved extra petals (sometimes trumpet-shaped, intermediate in appearance between petals and nectaries), which may be a different colour from the outer petals. These short, extra petals (sometimes known as "petaloids") drop off after the flower has been pollinated , leaving an apparently single flower, whereas doubles and semi-doubles tend to retain their extra petals after pollination. Gardeners and nurserymen have also created hybrids between less closely related species. The earliest
7420-437: The flower petals of the hellebore. As the hellebore beings to open, the aphids try to move into the flower. The aphids then feed on the inner parts of the plant as well as the young stems and shoots. As the population grows, the aphids eventually eat the remaining parts of the plant, such as older leaves, for food. Aphid infestations can be controlled through persistent squashing of the aphids manually or by using insecticides. It
7526-796: The flower petals. The symptoms were different from other leaf-spotting hellebore diseases, such as those caused by the fungus Coniothyrium and the bacteria Xanthomonas The case in New Zealand is the only reported case of P. viridiflava infecting hellebores so far, but in other plants P. viridiflava has been reported to also induce symptoms such as leaf rot, leaf blotch, stem necrosis and blossom blight. Hellebores are widely grown in United States Department of Agriculture hardiness zones 5a to 8b gardens for decorative purposes. They are particularly valued by gardeners for their winter and early spring flowering period;
7632-407: The flowers. Typically the fungus infects plants only through an open wound or when the plant is under stress, but it has also been known to infect plants in humid conditions. If the humidity is low, the mold may be contained to discrete spots on the plant, but the mold has been known to spread rapidly in highly humid conditions. Grey mold is not seasonally dependent and can infect a plant at any time of
7738-553: The following spring. Helleborus net necrosis virus (HeNNV), also known as Hellebore black death, is an RNA virus that can cause serious disease in Hellebore plants by stunting or deforming the plant as it grows. The disease marks the leaves of the hellebores with black streaks, often following the veins of the leaf, and creating ring patterns. It can also mark the sepals and flowers with black spots or streaks but does not always do so. When symptoms are severe, new leaves have limited growth before dying off. The most seriously affected in
7844-559: The form of black leaf spots, necrosis petal, and stem lesions. The most popular ornamental and commercial crop grown in New Zealand is H. orientalis and its hybrids, of which 90 percent of the H. orientalis in the Tauranga nursery contracted the disease after several days of moderate rainfall. The disease caused discoloration in the form of black leaf spots that were circular and about 1.5–2 mm in diameter, black stem lesions, and dry, grey to brown lesions with distinct margins on
7950-565: The fusion of gametes that have differing structure in at least one chromosome, as a result of structural abnormalities . A numerical hybrid results from the fusion of gametes having different haploid numbers of chromosomes . A permanent hybrid results when only the heterozygous genotype occurs, as in Oenothera lamarckiana , because all homozygous combinations are lethal. In the early history of genetics, Hugo de Vries supposed these were caused by mutation . Genetic complementation
8056-507: The genetic relationships between ducks are further complicated by the widespread gene flow between wild and domestic mallards. One of the most common interspecific hybrids in geese occurs between Greylag and Canada geese ( Anser anser x Branta canadensis ). One potential mechanism for the occurrence of hybrids in these geese is interspecific nest parasitism , where an egg is laid in the nest of another species to be raised by non-biological parents. The chick imprints upon and eventually seeks
8162-630: The genetically "pure" individuals with hybrids, hybridization could also save a rare lineage from extinction by introducing genetic diversity. It has been proposed that hybridization could be a useful tool to conserve biodiversity by allowing organisms to adapt, and that efforts to preserve the separateness of a "pure" lineage could harm conservation by lowering the organisms' genetic diversity and adaptive potential, particularly in species with low populations. While endangered species are often protected by law, hybrids are often excluded from protection, resulting in challenges to conservation. The term hybrid
8268-401: The hybrids are more fit and have breeding advantages over the indigenous ecotype or species. These hybridization events can result from the introduction of non-native genotypes by humans or through habitat modification, bringing previously isolated species into contact. Genetic mixing can be especially detrimental for rare species in isolated habitats, ultimately affecting the population to such
8374-454: The land area of Imperial Russia in 1914, including parts of Eastern Europe . One of Russia's main geopolitical interests lies in ever closer integration with those countries that it considers part of "Eurasia." The term Eurasia gained geopolitical reputation as one of the three superstates in 1984 , George Orwell 's novel where constant surveillance and propaganda are strategic elements (introduced as reflexive antagonists ) of
8480-442: The leaf blade or at the margins of the leaf. The spots continue to grow larger as the disease progresses, retaining an elliptical or circular shape and turning a dark brown or black color. The spots grow until they infect the whole leaf. Petioles and flowers can also be infected, but the disease is primarily seen in the leaves. The symptoms become visible in the spring and worsen with time. The small black fruiting bodies which carry
8586-658: The least-densely populated. Eurasia has been the host of many ancient civilizations, including those based in Mesopotamia , the Indus Valley and China. In the Axial Age (mid- first millennium BCE ), a continuous belt of civilizations stretched through the Eurasian subtropical zone from the Atlantic to the Pacific. This belt became the mainstream of world history for two millennia. New connections emerged between
8692-400: The loss of genetic diversity . Since the indigenous breeds are often well-adapted to local extremes in climate and have immunity to local pathogens, this can be a significant genetic erosion of the gene pool for future breeding. Therefore, commercial plant geneticists strive to breed "widely adapted" cultivars to counteract this tendency. Familiar examples of equid hybrids are the mule,
8798-632: The noted British nursery owners Helen Ballard and Eric Smith. In recent years, Ashwood Nurseries (of Kingswinford in the English Midlands ), already well known for its Ashwood Garden Hybrids ( H. × hybridus singles, semi-doubles, doubles and anemone-centres), has created hybrids between H. niger and H. thibetanus (called H. 'Pink Ice'), and between H. niger and H. vesicarius (called H. 'Briar Rose'). The gardenworthiness of these hybrids has still to be proven. The following hellebore species and cultivars have gained
8904-452: The number of chromosomes has been doubled. A form of often intentional human-mediated hybridization is the crossing of wild and domesticated species. This is common in both traditional horticulture and modern agriculture ; many commercially useful fruits, flowers, garden herbs, and trees have been produced by hybridization. One such flower, Oenothera lamarckiana , was central to early genetics research into mutationism and polyploidy. It
9010-420: The only remaining evidence of prior species, they need to be conserved as well. Regionally developed ecotypes can be threatened with extinction when new alleles or genes are introduced that alter that ecotype. This is sometimes called genetic mixing. Hybridization and introgression, which can happen in natural and hybrid populations, of new genetic material can lead to the replacement of local genotypes if
9116-438: The other (e.g., a bird hybrid might combine the yellow head of one parent with the orange belly of the other). Interspecific hybrids are bred by mating individuals from two species, normally from within the same genus. The offspring display traits and characteristics of both parents, but are often sterile , preventing gene flow between the species. Sterility is often attributed to the different number of chromosomes between
9222-573: The parent species), and hybrid swarms (highly variable populations with much interbreeding as well as backcrossing with the parent species). Depending on where a population falls along this continuum, the management plans for that population will change. Hybridization is currently an area of great discussion within wildlife management and habitat management. Global climate change is creating other changes such as difference in population distributions which are indirect causes for an increase in anthropogenic hybridization. Conservationists disagree on when
9328-537: The parent species. Cave paintings indicate that the European bison is a natural hybrid of the aurochs and the steppe bison . Plant hybridization is more commonplace compared to animal hybridization. Many crop species are hybrids, including notably the polyploid wheats : some have four sets of chromosomes (tetraploid) or six (hexaploid), while other wheat species have (like most eukaryotic organisms) two sets ( diploid ), so hybridization events likely involved
9434-506: The parents' common ancestor living tens of millions of years ago. Among insects, so-called killer bees were accidentally created during an attempt to breed a strain of bees that would both produce more honey and be better adapted to tropical conditions. It was done by crossing a European honey bee and an African bee . The Colias eurytheme and C. philodice butterflies have retained enough genetic compatibility to produce viable hybrid offspring. Hybrid speciation may have produced
9540-421: The plant. Insecticides may harm non-leaf miner flies if applied during the hellebore's flowering period. Macrosiphum hellebori , commonly known as 'Hellebore aphid' or 'greenfly', is a sap-feeding aphid that infests the flowers and foliage of hellebore plants. The whitish-green aphids are about 2–4 millimetres ( 3 ⁄ 32 – 5 ⁄ 32 inch) long and form dense colonies on hellebores, coating them with
9646-658: The plants are surprisingly frost -resistant and many are evergreen . Also of value is their shade tolerance. Many species of hellebore have green or greenish-purple flowers and are of limited garden value, although Corsican hellebore ( H. argutifolius ), a robust plant with pale green, cup-shaped flowers and attractive leathery foliage , is widely grown. So is the 'stinking hellebore' or setterwort ( H. foetidus ), which has drooping clusters of small, pale green, bell-shaped flowers, often edged with maroon, which contrasts with its dark evergreen foliage. H. foetidus 'Wester Flisk', with red-flushed flowers and flower stalks,
9752-637: The point of view of taxonomy , hybrids differ according to their parentage. Hybrids between different subspecies (such as between the dog and Eurasian wolf ) are called intra-specific hybrids. Interspecific hybrids are the offspring from interspecies mating ; these sometimes result in hybrid speciation. Intergeneric hybrids result from matings between different genera, such as between sheep and goats . Interfamilial hybrids, such as between chickens and guineafowl or pheasants , are reliably described but extremely rare. Interordinal hybrids (between different orders) are few, but have been engineered between
9858-496: The rose family ( Rosaceae ). The common name "hellebore" is first attested in 1300s; it originates, via Old French and Latin , ultimately from Ancient Greek : ἑλλέβορος , romanized : helléboros . Although traditionally translated as "plant eaten by fawns ", this could be folk etymology and, according to Beekes , really a Pre-Greek word. It is not related to the word " hell ", despite botanical associations with poison, madness, etc. In Anglo-Saxon England ,
9964-799: The species of the genus Helleborus , give its common name, the area of distribution, an image if available and the meaning of the scientific name. The cladogram shows the relationship between the different species determined with microbiological methods by Meiners et al. (2011). H. foetidus H. niger H. argutifolius H. lividus H. vesicarius H. thibetanus H. dumetorum H. purpurascens H. croaticus H. multifidus H. abruzzicus H. hercegovinus H. liguricus H. atrorubens H. viridis H. cyclophyllus H. torquatus H. orientalis H. odorus These four species have leaves on their flowering stems (in H. vesicarius
10070-419: The spores, pycnidia , are formed in the dead cells of the leaf spots. The spores are mainly spread by water, wind, and wind-blown rain. The fungus has an ideal habitat to spread and grow at the final growth site for hellebore plants, and if left untreated, the spores remain for many years. The most effective method against C. hellebori is to remove and destroy the infected leaves immediately to avoid reinfection
10176-515: The stems die back each year; it also has basal leaves). These species have basal leaves. They have no true leaves on their flower stalks (although there are leafy bracts where the flower stalks branch). Other species names (now considered invalid) may be encountered in older literature, including H. hyemalis , H. polychromus , H. ranunculinus , H. trifolius . Hybridising (deliberate and accidental) between H. orientalis and several other closely related species and subspecies has vastly improved
10282-516: The subregions of Eurasia from the Age of Discovery onwards, with the Iberians discovering new maritime routes in the 1490s, and the 1869 completion of the Suez Canal having paved the way for direct passage through the Indo-Mediterranean and the wave of Western European "New Imperialism" that dominated Africa and Asia until the mid-20th century. The communist presence in Eurasia (primarily driven by
10388-470: The term negative heterosis refers to weaker or smaller hybrids. Heterosis is common in both animal and plant hybrids. For example, hybrids between a lion and a tigress (" ligers ") are much larger than either of the two progenitors, while " tigons " (lioness × tiger) are smaller. Similarly, the hybrids between the common pheasant ( Phasianus colchicus ) and domestic fowl ( Gallus gallus ) are larger than either of their parents, as are those produced between
10494-483: The tunnels were dug. The larvae start to eat the inside of the leaves in August, and damage develops from the late summer to the early spring, with heavy attacks leaving the foliage disfigured by spring. To control heavy infestations, the leaves can be removed and destroyed during the winter months before the adult flies emerge. Insecticides can be used with limited effectiveness in controlling larvae and fly populations in
10600-400: The two parental mutant organisms are defective in different genes. If the hybrid organism displays a distinctly mutant phenotype, the two mutant parental organisms are considered to be defective in the same gene. However, in some cases the hybrid organism may display a phenotype that is only weakly (or partially) wild-type, and this may reflect intragenic (interallelic) complementation. From
10706-462: The two species. For example, donkeys have 62 chromosomes , horses have 64 chromosomes, and mules or hinnies have 63 chromosomes. Mules, hinnies, and other normally sterile interspecific hybrids cannot produce viable gametes, because differences in chromosome structure prevent appropriate pairing and segregation during meiosis , meiosis is disrupted, and viable sperm and eggs are not formed. However, fertility in female mules has been reported with
10812-587: The world are Java, Honshu, Great Britain, Luzon, and Sumatra. Other Eurasian islands with large populations include Mindanao, Taiwan , Salsette , Borneo, Sri Lanka, Sulawesi, Kyushu , and Hainan . The most densely-populated islands in Eurasia are Caubian Gamay Island , Ap Lei Chau , and Navotas Island . In the Arctic Ocean, Severny Island , Nordaustlandet , October Revolution Island , and Bolshevik Island are Eurasia's largest uninhabited islands, and Kotelny Island , Alexandra Land , and Spitsbergen are
10918-400: The year. The fungus forms black seed-like structures in the dead plant tissue to create its spores to help it survive when new host plants are scarce. The spores are spread through the air to new plants. To treat the infected plant, the first step is to remove infected and dying leaves, buds, and flowers immediately along with any other dead plant materials around the hellebore. The next step
11024-554: Was established by Carl Linnaeus in volume one of his Species Plantarum in 1753. The scientific name Helleborus could derive from the Ancient Greek word ἑλλέβορος ( helléboros ), the common name for H. orientalis , constructed from ἑλεῖν ( heleîn , "to injure") and βορά ( borá ), "food.". It is also possibly from Greek, ἄλκη “fawn”, βιβρώσκω (bibrṓskō, “to eat”). Twenty-two species are recognised and divided into six sections. The table below shows
11130-455: Was joined to Laurentia (now North America), to form Euramerica . This is a list of the longest rivers in Eurasia. Included are all rivers over 3,000 km (1,900 mi). All of the 100 highest mountains on Earth are in Eurasia, in the Himalaya , Karakoram , Hindu Kush , Pamir , Hengduan , and Tian Shan mountain ranges, and all peaks above 7,000 metres are in these ranges and
11236-541: Was probably H. × nigercors , a cross between H. niger and H. argutifolius (formerly H. lividus subsp. corsicus or H. corsicus , hence the name) first made in 1931. H. × sternii , a cross between H. argutifolius and H. lividus , first exhibited in 1947, is named after the celebrated British plantsman Sir Frederick Stern . H. × ballardiae ( H. niger crossed with H. lividus ) and H. × ericsmithii ( H. niger crossed with H. × sternii ) similarly commemorate
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