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Recently doing a little reading on interspecies hybrids I noticed that it seems interspecies hybrids are most often much larger than either parent. Notably, Ligers, Dzo and Savannah Cats, but it seems like all or at least most.

Is there a reason for this genetic expression in hybrids?

If I am incorrectly inferring this to be the case let me know that instead.

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up vote 4 down vote accepted

While they do not necessarily constitute the majority, it is true that there is a large number of interspecies hybrids whose members are larger in size than the parent species, and there exist explanations that account for this phenomenon.

What you are describing is an example of positive heterosis, or hybrid vigor. While the rationale for plants is more complex, it commonly arises between related species in mammals as a sort of heterozygote advantage in which the contrast in genetic contribution during conception spawns some phenotypic benefit. The exact implementation of this varies from species to species, but this link here is a nice, concise explanation for why ligers might be so large.

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