# Why can different tort species crossbreed?



## TheLastGreen (Jun 4, 2022)

This question has been bugging me for a while. We were tought that different species can't crossbreed, no matter what, due to speciation. Speciation mechanisms like unfertile hybrid crossings, different prebreeding needs like different mating calls or breeding at certain times of year etc. cause this. In the end if two organisms can produce fertile offspring, they are considered a species. So why can different tort species breed and produce offspring? A speciation method is the inability to copulate, but in some cases different torts can, which leads to hybrids. So could this be the answer?
A while back there was a taken down post of a leopard×sulcata hybrid, which produced offspring. It could be complicated that the other tort was a pure species (a sulcata or leopard) and that this could happen, but still it is confusing, which adds to my question on how this could happen?


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## TammyJ (Jun 4, 2022)

I guess it can sometimes happen, in some instances and situations, particularly with human input, but it SHOULD not happen because it is not natural and is likely to cause many issues including human differences and quarreling.


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## Markw84 (Jun 4, 2022)

TheLastGreen said:


> This question has been bugging me for a while. We were tought that different species can't crossbreed, no matter what, due to speciation. Speciation mechanisms like unfertile hybrid crossings, different prebreeding needs like different mating calls or breeding at certain times of year etc. cause this. In the end if two organisms can produce fertile offspring, they are considered a species. So why can different tort species breed and produce offspring? A speciation method is the inability to copulate, but in some cases different torts can, which leads to hybrids. So could this be the answer?
> A while back there was a taken down post of a leopard×sulcata hybrid, which produced offspring. It could be complicated that the other tort was a pure species (a sulcata or leopard) and that this could happen, but still it is confusing, which adds to my question on how this could happen?


The process of identifying species and "the people" who make those decisions has changed greatly in the past few decades. It used to be said that one of the definitions and basis of a separate species is inability to produce fertile offspring. That has changed totally. With the advancements in DNA gene analysis they now look at proposed species by enough markers in the DNA being different and the mitochondrial DNA showing a past definitive split in ancestry. But that is only one of the considerations. Also geographic isolation of populations is an important consideration eliminating the probability of any genetic mixing of the populations in the near past or future. Morphological differences are looked at seeing if visibly there is identifiable, consistent differences. AND... now that is even more confused by political pressures. Governments realize an endangered or critically endangered species is easier to get funding for and international status. So in the case of the Galapagos tortoises, for example, if the complex of domed tortoises is all considered one species with porteri, vicina, vandenburghi, midrophyes, etc all simply subspecies, with each under the species nigra. Then the species of nigra would have a lot more existing animals on the islands and the groups above would all be totaled together in looking at that. So the Ecuador government has petitioned strongly to keep portei, vicina, etc separate species so each species has a much smaller number of existing animals attributed to that species.

So we have many species that indeed can produce fertile offspring as their total DNA makeup is still close enough to match when the haploids of each parent merge. Yet there are visible, consistent differences, and the mitochondrial DNA shows a definite split in ancestry in the past, and populations of the two are separate enough to preclude mixing any more. Plus politics!

Nothing is simple anymore!


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## Maro2Bear (Jun 4, 2022)

If your question is HOW does this happen (in tortoises), I’m postulating that in the real world of Nature, out in the wilderness, it probably rarely happens because these two different species rarely meet up. They each occupy different eco zones. 

In the confines of a reptile keeper, two different species can easily be introduced in close unnatural conditions. If both animals are of reproductive age, size & compatible, successful mating is possible & has been demonstrated. This rarely happens in nature.


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