The fact that members of all of these groups readily hybridize would violate some interpretations of the concept of species. The article exposes the arbitrariness of the concept. Also, mtDNA and microsatellites (short stretches of repetitive DNA that expand and contract quickly) offer only a fragmentary picture of genetic history. It is unfortunate that the researchers were not able to use modern sequencing techniques, but in the case of museum samples these are sometimes not possible.

The existence of ring species says that there must be arbitrariness in deciding where to draw the line. See https://en.wikipedia.org/wiki/Ring_species for an explanation.

That said, where and when hybridization is possible is a complex question. For example consider the following pairs of species. (polar bears, brown bears), (horses, donkeys), (humans, chimpanzees). All are at about the same evolutionary distance from each other (current estimates are 5 million years, 4.5 million years and 6 million years). The bears happily interbreed, the equines interbreed but the babies are not generally fertile, and there are no reports of successful human/chimpanzee crosses. (No reports of anyone admitting to trying either, but it would be hard to believe that the attempt was nowhere made.)

Yet in all three cases, biologists generally agree that those are pairs of distinct species.

I learned of the Ivanov experiments after the topic of hybridization came up at a blog I used to follow: https://en.wikipedia.org/wiki/Ilya_Ivanovich_Ivanov

Misleading title: It sounds like they just found these turtles when in fact they just researched a group of turtles they already knew about, only to discover the group consisted of two different species - one of which is then of cause "new" to science.

But I guess that means that the group which - as far as I remember - was previously close to extinction before, now is even closer to extinction since there are even fewer of them left :(

I hope they don't do to it what they did to the giant squid when they discovered that too (kill it).

I read several articles on this. My recollection is that conservation of giant tortoises has been very successful and that identifying this as a separate species will most likely result in efforts to further increase members of this specific species. IIRC, it only has 250 members, much lower than the 2000+ members of the group it was thought to be part of. So identifying it as a separate species is expected to help increase their numbers.

They probably did a mouth swab or drew blood. Not hard to do without hurting the turtle.

I hope these are not as tasty as the first set we discovered

Looks like turtle soup is back on the menu, boys.