New Orangutan Species Discovered

This seems thoroughly unlikely on the face of it. I couldn't open the link from @DesertRhino150 but I found the following article which explains the scenario of it being distinct in simple terms, and in that article there is a link to the scientific paper which did open for me (so if you can't open the earlier link try the one in my article below). It is definitely interesting and seems solid enough.
New Species of Orangutan Is Rarest Great Ape on Earth

 

I'll be interested in how this plays out - whether it sticks or if it gets refuted with more study. I've seen the Bornean and Sumatran Orangutans, so I guess I'm going to have to try and go see this one as well if it actually is a distinct species.

The problem with all the splitting is that my percentage of "wild-seen" Asian primates keeps creeping downwards. I was on 50% of all species and now I'm on about 45%

 

But it was also pointing out that other well-supported species likewise show evidence of hybridisation.

 

It's an almost certainty that orangutans in Asian zoos are a mix of the two forms. The distance between the areas they occupy is small. I would suggest that it is highly likely rescue animals would already be amongst those released at the rehabilitation centres in northern Sumatra (within abelii range). It's also pretty likely that both forms are, to some degree, within foreign zoos' Sumatran orangutan populations.

 

This link has photos of all three, plus an easy chart-map to show the time-frame of the divergences. It's pretty easy to find photos of Tapanuli orangutans on the internet too (Tapanuli is a district quite separate from the more northerly populations, and the orangutans are a montane population, so have been studied quite a lot).
Pongo Tapanuliensis - www.batangtoru.org

Of the gene-flow between populations:

"Under our best-fitting model, we found evidence for post-split gene flow across Lake Toba (∼0.3–0.9 migrants per generation; Table S5), which is consistent with highly significant signatures of gene flow between P. abelii and P. tapanuliensis using D statistics"

"The existence of two deep evolutionary lineages among extant Sumatran orangutans was corroborated by phylogenetic analyses based on whole mitochondrial genomes (Figure 4A), in which the deepest split occurred between populations north of Lake Toba and all other orangutans at ∼3.97 Ma (95% HPD: 2.35–5.57). Sumatran orangutans formed a paraphyletic group, with P. tapanuliensis being more closely related to the Bornean lineage from which it diverged ∼2.41 Ma (1.26–3.42 Ma). In contrast, Bornean populations formed a monophyletic group with a very recent mitochondrial coalescence at ∼160 ka (94–227 ka)."

"The single available Y-haplotype from P. tapanuliensis was nested within the other Sumatran sequences, pointing at the occurrence of male-mediated gene flow across the Toba divide."

"Our analyses revealed significant divergence between P. tapanuliensis and P. abelii (Figures 3B and 4A) and low levels of male-mediated gene flow (Figures 3 B and 4B), which, however, completely ceased 10–20 kya (Figure 3C). Populations north and south of Lake Toba on Sumatra had been in genetic contact for most of the time since their split, but there was a marked reduction in gene flow after ∼100 ka (Figure 3C), consistent with habitat destruction caused by the Toba supereruption 73 kya [35]. However, P. tapanuliensis and P. abelii have been on independent evolutionary trajectories at least since the late Pleistocene/early Holocene, as gene flow between these populations has ceased completely 10–20 kya (Figure 3C) and is now impossible because of habitat loss in areas between the species’ ranges"

 

Most gibbons also hybridise freely and produce fertile offspring.

 

Here's an article arguing against the claim of the orangutan being a distinct species. It isn't very well written (there are two authors giving their viewpoints, and neither is convincing to me). Their basic argument seems to be that there is evidence of interbreeding and therefore all orangutans are a single species.

Some of their points are clearly debatable - e.g. the second author states as fact that there is only one species of gorilla (most primatologists now accept there being two species) and both state that neanderthals and humans are conspecific (a position heavily overshadowed by the position that they were separate species). This shows pretty obviously that they were never going to accept the Tapanuli Orangutan in the first place.

There's a very specific viewpoint repeated constantly in there too (and in the comments) that taxa which produce fertile offspring when interbreeding must be single species, which obviously calls into question where they would stand on canids, ducks, macaws, and any of those other groups which hybridise freely and produce fertile offspring.

Also, I just have to repeat a bit from the comments (by the main author) where he says "That, in fact, is exactly what zoos are doing making “cocktail orangs” by breeding Sumatran and Bornean orangs. They’re trying to keep the genetic diversity of both populations in captivity."

A new species of orangutan? I doubt it.

 

Same here. My initial thought was that having two orangutan species on Sumatra was ridiculous, but the paper and the explanations within it seems good to me. I'm not wholly convinced it's a distinct species, but at the moment I'm happy to accept it.