The Bonobo territory, criss-crossed with rivers
Bonobos are cousins of the common chimp, famous for being less violent and more sexually liberal than their spear-wielding relatives. Genetic data indicates the two groups diverged around two million years ago; around the same time the Congo river formed and cut them off from one another. But the Congo isn’t the only river in the region and Bonobo territory has been cut up by more rivers (most of which feed the Congo). Might this be leading to another divergence in the chimp family?
Short answer: not yet. A pair of Australian researchers have been looking into variation amongst Bonobo populations isolated by 4 rivers in the region; and whilst they did detect differences in the skull 84-97% of this could be accounted for by within-group variation. In other words, the populations were no more different from each other than from people Bonobos within their own group.
However, they did find an increased level of differences between two of the populations in question. Although nowhere near enough to classify them as a new species (or even sub-species); it does suggest that this branch of the ape family is continuing to evolve and diversify. When we look back at chimps as unchanging representatives of our ancestors, odds are we’re wrong. They evolved too.
Reference
Pilbrow, V., & Groves, C. (2013). Evidence for Divergence in Populations of Bonobos (Pan paniscus) in the Lomami-Lualaba and Kasai-Sankuru Regions Based on Preliminary Analysis of Craniodental Variation. International Journal of Primatology, 1-17.
EvoAnth 
All of this raises the question: How do you define a species, Adam? As far as I am aware Pan troglodytes and Pan paniscus have successfully interbred (in captivity). Perhaps, technically, they are still one species according to the Biological Species Concept.
The biological species concept is commonly misunderstood. The biological species concept is that in pristine nature, species will be reproductively isolated from each other. There is the assumption that individuals who hybridize have reduced fitness compared to non hybridizers. This works pretty well when the species are syntopic. Syntopic means they ordinarily encounter each other and could interbreed if they wanted to. When populations do not occur together, the concept is less helpful.
There are premating and postmating isolating mechanisms. If premating isolating mechanisms are strong, there is little selection for evolution of postmating isolating mechanisms. One sees all kinds of things going on in freshwater fishes.
There is a well documented instance where highway construction mudded up a stream occupied by red shiners and blacktail shiners. A hybrid swarm, including F1, F2, and backcross individuals developed. This swarm persisted until the stream cleared back up. It disappeared, and we now have two good species again.