Well i might as well. Here's the full report since my website is always swammed with popups and such. LOL
My Liger and Tigon report. Ask me for bib if u need it....
The Importance of Hybrids
Hybrids like ligers and tigons that live in hybrid zones are less fit, but act as safeguards from extinction of pure species like tigers and lions. Hybrids form when two different species mate where their mating zones cross (Purves 490). This mating zone is called a hybrid zone (Purves 491). To produce a hybrid, chromosomes from both parents need to pair off evenly during meiosis (Guynup 3). Given the chance, lions and tigers can breed and form fertile hybrids, ligers and tigons. Ligers and tigons show blended traits, from social lion behavior to independent tiger behavior (Green Apple). Hybrids’ importance is generally disregarded and ignored by everyday people (Barton 134). Tigon isn’t even a word in English. Hybrids lack Genus species names (Mayr 133). However, hybrids have special importance to evolution; hybrids defy extinction and institute safeguards for the survival of pure species. These safeguards exist as part of evolution and speciation. The definition of a species became less general to exclude hybrids (Pw 4). The “potentially reproduction” definition, which has existed since 1943 and up until 1978 (Guynup 3), would lump tigers and lions as one species because they can successfully produce a fertile offspring (Pw 3). Hybrids’ existence is bewildering. Hybrids are less fit; often they are sterile, more susceptible to diseases, and live shorter (Lemmon 177). Nonetheless, hybrids help species’ survival (Jiggins 3). Evolution, speciation in particular, has bended to produce a safeguard that protects species from extinction.
Hybrids test the theories of evolution and speciation (Ezzell 102). This test generates a safeguard, hybrids. Hybrid zones exemplify “evolution in progress” says Elaine Hoagland. “You can go overboard in trying to freeze what exists now.” Hoagland explains. Hybrids violate species boundaries and stop divergence (Arnold 12). In evolutionary terms there is a reason hybrids both progress and freeze evolution. Sometimes the fittest species isn’t the two new species produced by speciation, but the original species, the hybrid. The lines between two species are conventionally drawn when neither species can successfully reproduce with the other (PBS). Nevertheless, successful interbreeding is the key to defining what is a species (PBS). Tigers and ligers can mate and create fertile offspring; however, the majority of male hybrids are sterile. Therefore, mating can be considered unsuccessful, or less successful than pure species mating. The recent emphasize on successful interbreeding illustrates that lions and tigers are separate species; although, they can produce fertile hybrids. Studies of fossil populations using morphological, biochemical, and molecular markers reveal that modern and ancient hybridization affects the distribution of genetic variation (Critchfield 110). Speciation is a geographical mechanism that exists due to an alteration in environment (Rosenzweig 1622). Because hybrids exist, speciation appears rough on a fine scale, but it loses irregularity when viewed on the grandest scale (Rosenzweig 1622). When looked on the grand scale of evolution, hybrids are the exception to speciation. The fabrication of hybrids adds to the genetic variability and therefore evolution of a species. With more genetic variability, lions and tigers are provided with a safeguard against extinction. Evolution and speciation have created separate species that are still bonded to their hybrid ancestors. This bond exists as a safeguard and tests theories of evolution and speciation.
Hybrids are usually inferior so why do they exist? Darwin said in his Origin of Species “Pure species … when intercrossed they produce either few or no offspring, hybrids, on the other hand, have their reproductive organs functionally impotent….” In the wild, different species rarely interbreed for one reason: The offspring are usually infertile, which spells extinction for the new hybrid species (Guynup 1). “Infertile offspring don’t pass on their genes [hereditary instructions in all cells] to the next generation,” says biologist Judith Rhymerat (Guynup 1). The genes found in hybrids can lack survival traits and result in an infertile offspring. Mayr extended this view “The majority of … hybrids are totally sterile.” “Even those hybrids that produce normal gametes in one or both sexes are nevertheless unsuccessful” said Mayr. When hybrids backcross to the parental species, they often produce genotypes of inferior viability (Ezzel 102). The life span of many hybrid big cats is short and prone to cancers and other illnesses. Successful hybridization is rare among animals. Hybrids are almost always weaker in a uni-modal model (Arnold 14). Notropis cornutus and Notropis chrysocephalus in a study, by Dowling and colleagues was, found to be less fit as hybrids (Arnold 12). Caledia captiva hybrids show that a selection against hybrids exists; this was proven by Shaw and colleagues (Arnold 13). Helianthus annuus and Helianthus periolaris, in an experiment by Arnold, Hodges, and colleagues, showed a strong selection against hybrids (Arnold 14). The strengthening of prezygotic isolation, reinforcement, is present when hybrids are not selected against (Anderson 5). The mechanisms that could reinforce this prezygotic isolation make it hard for hybrids to survive (Anderson 5). In the absence of reproductive, character displacement is not evidence against the operation of reinforcement (Anderson 5). Selection against hybridization is expected to generate prezygotic divergence in unimodal hybrid zones (Smadja 165). In the uni-modal model almost all hybrids die due to inferior genes (Lemmon 177).
Ligers and tigons are hybrids that exist because of evolution. Tigers and lions will court, mate, and can produce fertile ligers and tigons. Animalia Chordata Mammalia Carnivora Felidae Panthera leo, lions fan out to encircle its prey. Animalia Chordata Mammalia Carnivora Felidae Panthera tigris, tigers stalks their prey from behind. Ligers and tigons both encircle and stalk. Lion litters are usually two or three cubs. Tiger litters are usually one or two cubs. Liger and tigon litters are usually four or more cubs. Lion cubs are the last to eat in the pride. Tiger cubs eat before their parents. Ligers and tigons cubs eat before their parents (Barrett 114). In times of food shortage, adult lionesses keep their own cubs from eating. Tigers save the best cut for their cubs. Ligers and tigon cubs are given the tenderest cuts (Lair Web). Lions live in prides. Tigers generally live and travel alone. Confusion between the social lion personality and solitary tiger personality is recorded (Lair Web). Li-tigons converse in lion while ti-tigon converse in tiger. Male ligers and tigons are infertile, but females may go on to produce offspring. Ligers are the world’s biggest cats (Barrett 114). Tigons are often smaller than both of their parents. Ligers display hybrid vigor. Tigons display dwarfism. As ligers grow older their stripes fade. As tigons grow older they grow more stripes. Keepers say that ligers act more like lions than tigers and that tigons act more like tigers than lions. Ligers are more common than tigons because the mating process is easier (Greenapple). If a liger or tigon is a male, it will have a leonine mane, but it will not be as defined as a lion’s. Both ligers and tigons make the sound of both lions and a tigers. Ligers and tigons generally inherit a love of the water which comes from their tiger parent, but it can take some time for the tiger side of their personality to convince the lion side that water is a great thing (Lair Web). Ligers are gentle and easy going. No fertile ligers have yet to be found (Lair Web). Both hybrids’ lifespan are shorter than either lions or tigers. Both hybrids are prone to cancers and many other illnesses. The tigons’ and ligers’ unique blend of physical and mental characteristics resembling both parents fits into a bimodal hybrid zone model. A bimodal hybrid zone is where populations predominantly consist of individuals genetically similar to one or the other parental genotype, with few intermediates (Jiggins 1). Lions and tigers exist in a bimodal hybrid zone in which lions and tigers are predominating, with their hybrids much less occurring. The occurrence of bimodality suggest that adaptive evolution of mating is more likely than generally supposed, because almost complete linkage disequilibria between mate choice and trait loci already exists in many such zones. Because ligers and tigons show physical and mental traits of both lions and tigers they exist in a bimodal model.
Hybrids and hybrid zones exist as an evolutionary safety net against the enemy of evolution, extinction (Guynup 4). In a bimodal model some rare hybrid genotypes possess better fitness and are analogous to a rare mutation that conveys a selective advantage to its carrier (Arnold 5). Hybrid vigor makes some hybrids, like ligers, stronger and better adapted to their surroundings than their parents (Guynup 4). A distribution of the parental genotypes into a random pattern in nature reflects that habitat selection favors one parent over the other in different niches. Hybrids can be viewed as a different species fighting for their niche. The Tension Zone or Dynamic-Equilibrium model shows that the stability of hybrid zones reflects an equilibrium between the selection against hybrid individuals and continual dispersal of parental genotypes into the zone of overlap. As long as there is an overlap in mating zones hybrids will go on and exist. In bimodal models hybrids show similar or better survival rates. There is evidence that certain hybrid genotypes possessed increased fitness (Rosenzweig 1622). Rosenzweig said that “… a small percentage of alien genes do appear to interact favorably in hybrids.” Grant made interesting conclusions when he revisited Darwin’s finches. Before El Nino, hybrid individuals were rare and did not reproduce successfully. But this changed after El Nino. Hybrid finches possessed novel beak morphologies that facilitate more effective use of the new array of seeds (Grant 503). This resulted in high levels of reproduction (Grant 503). Thus, hybridization enhanced genetic variation by adding hybrid genotypes that in this case were more fit in a novel habitat. Wooten and colleagues proved that Gambusia hybrids are fitter (Arnold 15). Freeman and colleagues proved that Mountain Big Sagebrush hybrids are fitter (Arnold 16). Anderson and colleagues found proof to support the hypothesis that certain hybrid genotypes are adapted to novel environments (Arnold 18). Natural hybridization may positively affect changes in the genetic diversity, population dynamics, and interactions between the hybridizing forms and other species. Hybrids also have a significant effect on the genetic structure of rare taxa when the rare taxa comes into contact with more numerous relatives (Arnold 16). The most important thing hybrids do is act as a safeguard for the genetic enrichment of the endangered form. One example of the use of the hybrid safeguard is the hybridization of the Florida panther. “The USFWS could either have hybridized the Florida panther or let it go extinct” said Rhymer. Hybrids like ligers and tigons that live in hybrid zones are less fit, but act as safeguards from extinction of pure species like tigers and lions.
 Hybrid formed when a male lion mates with a female tiger.
 Hybrid formed when a female lion mates with a male tiger.
 According to Webster’s Dictionary for the English Language.
 Hoagland is the National Executive Officer Council on Undergraduate Research (CUR)
 Every male liger and tigon on record is sterile.
 The grand scale of evolution is based on all of life’s evolution.
 Judith Rhymerat is an expert in species genetics.
 Ernest Mayr is Alexander Agassiz Professor of Zoology, Emeritus, at Harvard University.
 The assumption that hybrids are all sterile is not correct. Most female hybrids are not sterile.
 Examples of this are Li-tigons, Ti-tigons, Li-ligers, and Ti-ligers.
 Hybrid formed form a male lion and a female tigon
 Hybrid formed form a male tiger and a female tigon
 Ligers and tigons usually do not like swimming until they are 2.
 Extinction is part of evolution but its existence limits the evolution a certain species can make.
 They are better adapted in certain areas.
 Rosenzweig is an expert in speciation.
 Grant did an extensive study on Galapagos island finches.
 El Nino changed the environment of the island.
 Rare taxa means rare species.
 Dr. Judith Rhymer is a university of Maine faculty member and Us Fish and Wild Life Service advisor.
Last edited by Inuyasha on Mon Apr 20, 2009 5:27 am, edited 1 time in total.
i have found your discussion of utmost interest and it has motivated me to post a reply and also use TIGON as my username. pls can i ask where i can find these amazing creatures as am thinking of adopting one. can i ??????? they are so beautiful
LOL u probably won't be able to adopt one because the only tigons in the world are already privately owned. Besides the monetary value of them range from 15 to 100 million. Not to mention that no sellers would be able to part from their one of a kind procession. Plus u would have to live in a country that allowed u to adopt wild animals. In the US that's not legal.
Sorry if im a bit late on the bandwagon but I'm new so i guess that excuses me ...
anyone seen napoleon dynamite?
Deb: What are you drawing?
Napoleon Dynamite: A liger.
Deb: What's a liger?
Napoleon Dynamite: It's pretty much my favorite animal. It's like a lion and a tiger mixed... bred for its skills in magic.
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