75-473: Arctocephalus gazella Arctocephalus townsendi Arctocephalus philippii Arctocephalus galapagoensis Arctocephalus pusillus Arctocephalus forsteri Arctocephalus tropicalis Arctocephalus australis The genus Arctocephalus consists of the southern fur seals . Arctocephalus translates to "bear head." The number of species within the genus has been questioned, primarily based on limited molecular data. The issue
150-475: 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,
225-463: 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 )
300-505: A 10-day window. Pups are weaned at about four months old. Juveniles may then spend several years at sea before returning to begin their breeding cycles. The ecology of Antarctic fur seals during the non-breeding winter is poorly understood. Adult and subadult males may form groups while moulting along the Antarctic Peninsula in late summer and early autumn. Adult females are gregarious but relatively asocial other than
375-564: 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,
450-515: 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
525-509: 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
600-740: A decrease (e.g. Bouvet Island). Antarctic fur seals have a circumpolar distribution and breed from 61° S to the Antarctic Convergence . Breeding colonies are found at South Georgia and the South Sandwich Islands , South Orkney Islands , South Shetland Islands and Bouvet Island in the Southern Atlantic Ocean ; Marion Island , Crozet Islands , Kerguelen and Heard Island in the Southern Indian Ocean ; and Macquarie Island in
675-509: 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
750-407: 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 a hybrid is interpreted differently in animal and plant breeding, where there is interest in
825-602: 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
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#1732797394950900-548: 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
975-439: 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
1050-498: 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,
1125-736: A maximum observed for female of 24. Antarctic fur seals are believed to be the most abundant species of fur seal . The largest congregation occurs on the island of South Georgia in the southern Atlantic Ocean, which holds approximately 95% of the global population . The current best estimate of the South Georgia population is between 4.5 and 6.2 million animals. Bouvet Island has the second largest population with 46,834 animals. However, there are regional differences in population trends: some colonies are increasing in size (e.g. Kerguelen Islands , McDonald Islands ), some are stable (e.g. Macquarie Island , Heard islands), and some are showing
1200-432: 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
1275-422: A physician with the relevant experience in treating exotic animal bites. This issue is compounded by the complexity of fur seal behavior and how serious a bite can be and the risk of transfer of diseases. The implication for Antarctic Fur Seals but this species is considered to be one of several pinnipeds at high risk of future disease outbreaks because of their tendency to congregate in large dense aggregations and
1350-405: 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,
1425-613: A third of the Antarctic Fur Seal pups born at sites in the South Shetland Islands. Levels of predation may be high enough to cause a population decline at these sites. As well as the effects of hunting and fishing , the numbers of humans visiting the Antarctic and sub-Antarctic each year for tourism and scientific expeditions have risen. This increase in visits has led to greater interaction between
1500-498: A very small number of partially leucistic Antarctic fur seals have been found. Males are substantially larger than females. Males grow up to 2 m (6.5 ft) long and with a mean weigh of 133 kg (293 lb). Females reach 1.4 m (4.6 ft) with a mean weight of 34 kg (74.9 lb). At birth, mean standard length is 67.4 cm (58–66) and mass is 5.9 kg (4.9–6.6) in males and 5.4 kg (4.8–5.9) in females. Antarctic fur seals live up to 20 years with
1575-464: A western region including the islands of the Scotia Arc , Bouvet Island , and Marion Islands , and an eastern region, including Kerguelen and Macquarie Islands . Seals from Crozet Islands and Heard Island are mixtures from both regions. The fur seal is a midsized pinniped with a relatively long neck and pointed muzzle compared with others in the family. The nose does not extend much past
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#17327973949501650-577: 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
1725-407: 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
1800-571: 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
1875-659: 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
1950-451: 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
2025-677: Is complicated because some of the species are able to produce fertile hybrids . A recent review recommended the retention of seven species, deprecating the New Zealand fur seals to a subspecies of the South American fur seal, while also questioning the status of the Guadalupe fur seal. Other recent studies have indicated the genus may be paraphyletic , and some taxonomic reshuffling was previously done to account for this; however, more recent studies support it being monophyletic , with
2100-552: 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
2175-536: Is one of eight seals in the genus Arctocephalus , and one of nine fur seals in the subfamily Arctocephalinae . Despite what its name suggests, the Antarctic fur seal is mostly distributed in Subantarctic islands and its scientific name is thought to have come from the German vessel SMS Gazelle, which was the first to collect specimens of this species from Kerguelen Islands . Antarctic fur seals are member of
2250-830: Is protected by the governments in whose waters it resides ( Australia , South Africa , France ) and by the Convention for the Conservation of Antarctic Seals in waters south of 60° S. The animal is also listed in Appendix 2 of CITES. To learn more about Antarctic fur seal visit: Hybridisation (biology) In biology , 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
2325-453: Is still a persistent problem, but it has halved in recent years. Trawling activities developing around Macquarie Island may affect the prey base of the primarily fish-eating Antarctic fur seals that breed on those islands. Recent work indicates that there is significant overlap between foraging areas and fisheries activities, suggesting a potential for competition for prey resources may exist. Leopard seals have been noted to take as many as
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2400-427: 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
2475-515: 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
2550-619: The IUCN Red list is 'decreasing' and it has been suggested that this decline is due to the effects of global climate change on prey availability . Historically the species were decimated by the sealing industry for its fur and its population was driven close to extinction by the 19th century. Since sealing operations ceased in the early 20th century, the species has recovered at different rates across its former geographic range. Waters inhabited by Antarctic fur seals are exploited by few fisheries, but these may expand in their range in
2625-653: 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
2700-472: 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
2775-438: 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
2850-557: The Antarctic Fur Seal is polygynous , and dominant breeding males mate with as many as 20 females during a successful season. Males establish breeding grounds in October to early November. Females generally reach the colonies in December and give birth to a single pup several days later. Gestation lasts between 8 and 9 months and it has been observed a high breeding synchrony across the species' range, concentrating 90% of pup births in
2925-506: 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
3000-603: The Southern Pacific Ocean . During winter , Antarctic fur seals range widely from the Antarctic continent to the Falkland Islands , and southern Argentina reaching as far as the Mar del Plata and Gough Island. Antarctic fur seals are one of the better-studied Southern Ocean predators. However, the vast majority of information has been collected during summer breeding months. The breeding system of
3075-453: The alleged paraphyly being a consequence of incomplete lineage sorting . [REDACTED] 700,000–1,000,000 [REDACTED] [REDACTED] [REDACTED] [REDACTED] 10,000 [REDACTED] [REDACTED] 1,060,000 [REDACTED] [REDACTED] [REDACTED] [REDACTED] [REDACTED] Arctocephalus gazella The Antarctic fur seal ( Arctocephalus gazella )
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3150-479: The breeding season. Nursing mothers near South Georgia are dependent on krill during the breeding season, therefore the availability of krill is important to the reproductive success of this animal. The colonies at Macquarie Island and the Kerguelen Islands rely more on a diet of fish and squid . Antarctic fur seals dive at night to feed. South Georgia islands, which hold approximately 95% of
3225-524: 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,
3300-426: 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
3375-547: 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
3450-481: 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
3525-400: 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
3600-444: 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
3675-407: 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
3750-413: 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
3825-499: The effect of environmental changes associated with global warming on the spread of diseases. Finally, the 19th century population bottleneck led to reduced genetic diversity, leaving it again more vulnerable to disease and stresses of climate change . In particular, the Antarctic fur seal's primary prey base, krill , could be reduced as a result of ocean acidification , or the distribution could be altered by climate change. IUCN Conservation status: Least Concern. The species
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#17327973949503900-611: 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"
3975-429: 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
4050-565: 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
4125-485: The future. A 1997 study at South Georgia indicated that several thousand Antarctic fur seals were entangled in man-made debris such as discarded fishing line, nets, packing bands and anything that can form a collar. Consequently, CCAMLR campaigned for compliance with MARPOL provisions relating to waste disposal at sea, and for cutting of any material jettisoned which could form collars to entangle seals. Subsequent monitoring of entangled fur seals confirmed that entanglement
4200-507: 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
4275-630: 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
4350-636: The genus Arctocephalus . Recently, a proposal was made to reassign this species to the resurrected genus Arctophoca . Antarctic fur seals may be confused with southern otariids that share their range, like Subantarctic ( A. tropicalis ), New Zealand ( A. forsteri ), and South American fur seals ( A. australis ), and the Juan Fernandez fur seal ( A. phillippii ), as well as the South American ( Otaria flavescens ) and New Zealand sea lions ( Phocarctos hookeri ). Genetic studies on population structure suggest that there are two genetically distinct regions:
4425-418: The global population, had a total population in 1999/2000 between 4.5 and 6.2 million. The South Georgia population reached carrying capacity fairly recently and may thus be spilling over into relatively nearby, lower density sites. However, the abundance of adult females is estimated to have declined by some 30% between 2003 and 2012, and by 24% since 1984 to around 550,000. The population trend according to
4500-401: 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
4575-407: 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
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#17327973949504650-457: The local fauna and humans. With this greater interaction comes the risk of affecting the territoriality of seals especially during the mating season . This can also increase the possibility of 'exotic' injuries to humans. In 2015 a man was rescued from a South Georgia Island by British Forces after receiving a serious bite from a fur seal. Due to the remote location of where these injuries occur, this can lead to complications in getting people to
4725-400: 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,
4800-587: The mouth, the external ears are long, prominent, and naked at the tip. Adults have very long vibrissae , particularly males, up to 35 to 50 cm. The fore flippers are about one-third, and hind flippers slightly more than one-fourth of the total length. Adult males are dark brown in colour. Females and juveniles tend to be paler, almost grey with lighter undersides. Colour patterns are highly variable, and scientists reported that some hybridization between Subantarctic and Antarctic fur seals has occurred. Pups are dark brown at birth, almost black in color. However,
4875-452: 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
4950-420: 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
5025-438: 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
5100-573: 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
5175-537: 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
5250-506: 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
5325-637: 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
5400-1149: The strong bond they establish with their pups, although there are occasional aggressive encounters with nearby females or other pups and brief interactions with adult males to mate. These seals appear to be solitary when foraging and migrating. The usual food source for individuals in the Atlantic Region is Antarctic krill ( Euphausia superba ); while in the Indian Ocean the diet is mostly based on fish and squid . The fish prey are principally myctophids , icefish , and Notothenids, although skates and rays are also consumed. Penguins are occasionally taken by Antarctic fur seal males. Seasonal differences in diet have been recorded across colonies, seasons and years. Studies have showed that female Antarctic fur seals can undertake wide-ranging foraging migrations during winter. Interannual differences appear to be related to differences in local oceanographic conditions. Antarctic fur seals feed primarily on krill , fish , and squid . Birds are eaten occasionally outside
5475-470: 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
5550-400: 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
5625-462: 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
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