Wild Animals/Hybridisation

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Question
I'm interested to know about some certain aspects involving cross breeding or hybridisation between different species of the same genus, i.e. chimpanzees and gorillas or horses and donkeys or wolves and coyotes or lions and tigers, etc. My question involves the effect known as 'heterosis', firstly I'd like to know if all of the F1 progeny would display the effects of heterosis, (is hybrid vigour the same thing?) and would heterosis result in progeny that were very much larger or even giant size compared to either of their parents?
Secondly I would like to know that if there were three species within a genus and a combination of say species A mated with species B and created a fertile hybrid that displayed effects of heterosis, i.e. much larger sized progeny, (lets call it hybrid A), then say species B mated with species C and also produced a fertile hybrid (hybrid B), which also displayed heterosis effects, (as in a much larger sized progeny) and then if a hybrid A was mated with a hybrid B, would heterosis again be possible in the F1 or even subsequent generations of the hybrid AB progeny and would that then mean that the oversized hybrid AB progeny, (lets call it hybrid C) would then be up to double the size or even larger than the original species A, B or C grandparents and would subsequent cross breeding of hybrid C with any of its parent or grandparent species also result in any effects of heterosis, so that even larger hybrids could then be bred and so on and so on until mega fauna sizes could be produced?

Answer
Dear Peter

Thank you for your question. I also wish to thank the authors of the websites I used. Please note that chimpanzees and gorillas belong to different genera.

Most of the information below comes from an article by Eugene McCarthy (http://www.macroevolution.net/heterosis.html) and I hope that it answers your questions. Lotsy noted hybrids of snapdragons (Antirrhinum) had characteristics differing from those of the original parents. When Lotsy crossed Antirrhinum glutinosum and A. majus, individuals in the F₂ generation had flowers like those seen in the related genus Rhinanthus.  In the F₄ generation Lotsy stabilized a new, true-breeding type.
The California redwood (Sequoia sempervirens) is thought to be a hybrid of the giant sequoia (Sequoiadendron giganteum) and dawn redwood (Metasequoia glyptostroboides), but is taller than both of them and is a good example of heterosis, as described in your question. Hybrids between the Bactrian camel (Camelus bactrianus) and dromedary (C. dromedarius) are partially fertile and are larger, more tolerant and easier to work with than either parent.  Hybrids between the Siberian crane (Grus leucogeranus) and white-naped crane (G. vipio) are bigger than either parent. The hybrid produced by a lion and a tigress (a "liger") is usually larger and stronger than either parent, but the cross between a tiger and lioness (a "tigon") tends to be smaller than either parent. Grant and Grant showed that hybrid Galapagos finches (Geospiza) were better able than their parents to feed on seeds after an El Niño event.
Some sunfish (Lepomis) hybrids are more vigorous and aggressive than their parents. Manwell and colleagues showed that this positive heterosis was at least partly due to the enhanced blood chemistry combining factors from both parents.
If a hybrid derived from a cross between two parents is crossed with a third type of parent, the compound hybrid can have traits that are not intermediate between those of the first two parents.
It seems that heterosis varies with different hybrids. The examples given above only represent a small sample of the hybrids produced from closely related species. By choosing the larger hybrids, it is possible that you could breed even larger hybrids, but the following website seems to indicate this is unlikely. http://www.neanderthalproject.com/?tag=heterosis says that the hybird stock is often larger than either parent, but this need not confer greater fitness. Ligers grow larger than lions or tigers, probably due to “gene imprinting,” as the growth-regulating signal, usually passed by genes from the female lion, are not present in the mating tigress. The hybrid vigour effect (heterosis) begins to fade immediately after the first generation of offspring. While some gene combination may lead to improved reproductive success and an improved line, subsequent generations of young in the new line show variations in fitness as the new line will be swapping and permuting the new gene set within itself or with itself and either or both of its parent species. This suggests that if you breed hybrid C with its parent or grandparent species, there is less chance of it reaching mega fauna size than in earlier crosses. This could be due to a number of reasons, such as the limbs of the hybrid being unable to support the larger body.   

I have been to Neanderthal and Munich, which have examples of 'aurochs' and 'tarpans' produced by choosing animals with similar traits to the original animals. There is also work in South Africa, where zebras are being bred to produce animals resembling the quagga.

I hope this helps

All the best

Jonathan

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Jonathan Wright

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I can answer questions about wild mammals and other animals, as well as extinct animals and zoos. I am not an expert about every animal species. I can look up information from books and the internet, but can't verify if all the information is true. Please don't ask questions about: 1. Pets. I am not a vet. Please contact a vet if your pet is ill. You may need to spend some money if you want your pet to live. Don't get a pet if you don't know how to look after it and if you can't provide it with the space, food and possible companions that will help it live a healthy life. Don't take animals from the wild, unless they are ill and/or injured and you can protect them until a wildlife charity can help. It is cruel to take animals from their parents, especially if the parents will look for the babies, while putting their other babies at risk. You may be breaking the law by keeping wild animals or you may need a licence to look after some species. Please check with a local wildlife group. 2. Eggs: Please don't remove eggs from nests. The mother birds provide the right temperature for the eggs and won't sit on them if the temperature is warm enough for them to develop naturally. It is illegal to remove eggs of some species and, unless you have an incubator or a broody hen, the egg may not develop. If you are allowed to touch the eggs, you can candle them to see if they are fertile. If theys aren't fertile, they won't hatch. 3. Fights: Please don't ask about fights between different animals. These questions assume that individuals of two species fight each time they meet and that one species will always be victorious over another. This is untrue. There are cases where a live mouse has been fed to a venomous snake, bitten the snake leading to the snake's demise. 4: Diseases: Please ask doctors or other medical experts about diseases that you may catch from animals. I can't advise on how to deal with viruses, bacteria etc.

Experience

I have a zoology degree and have been interested in animals since I was two. I am a zoo volunteer at London Zoo. I have appeared on a BBC Radio Quiz, 'Wildbrain'.

Organizations
WWF. ZSL. Natural History Museum. RSPB. London Bat Group.

Publications
Newsletters of London Zoo volunteers and the London Bat Group

Education/Credentials
BSC degree in Zoology. 'A' level in Zoology. 'O' Level in Biology.

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