Someone wrote to say that the ensatina is not a good example of ring species because where the ring comes together there have been instances of eschscholtzii and klauberi interbreeding. I agree, I should have used just the second example I gave, the greenish warbler. Unlike ensatina, there are no instances of the end species, plumbeitarsus and viridanus, interbreeding.
Sources for the ensatina ring:
Closing the ring: historical biogeography of the salamander ring species Ensatina eschscholtzii Kuchta et al FEB 2009 Journal of Biogeography
"Evolutionary Relationships Within the Ensatina Eschscholtzii Complex Confirm the Ring Species Interpretation" Systematic Biology January 11, 1992.
"Is Ensatina eschscholtzii a ring-species?" -- R Highton, Herpetologica, 1998
Sources for the Warbler ring:
Speciation in the round David B. Wake, Nature, 18 Jan 2001
PHYLOGEOGRAPHIC BREAKS WITHOUT GEOGRAPHIC BARRIERS TO GENE FLOW Darren E. Irwin, Evolution, 2002
"Ring species as bridges between microevolution and speciation" D Irwin et al, Genetica, 2001
Someone asked me to make a short version of this video, leaving out all the derisive stuff and just showing the mechanism of ring species. I got a message echoing that request, because the requesters want to use the video educational ammunition against creationist friends. If that need is shared by others I will be happy to do this, but using the example of the greenish warbler rather than the ensatina.