Ben Stein to take on Darwinism on April 18

[Final-Fan]

OK, now I was talking with Grey Acumen a while back about this topic and his definition of a species change was when one population could no longer successfully breed with another. Considering that lions and tigers can have fertile offspring I disagree with that one, but I found a study that met the requirement of speciation by that definition:

In 1964 five or six individuals of the polychaete worm, Nereis acuminata, were collected in Long Beach Harbor, California. These were allowed to grow into a population of thousands of individuals. Four pairs from this population were transferred to the Woods Hole Oceanographic Institute. For over 20 years these worms were used as test organisms in environmental toxicology. From 1986 to 1991 the Long Beach area was searched for populations of the worm. Two populations, P1 and P2, were found. Weinberg, et al. (1992) performed tests on these two populations and the Woods Hole population (WH) for both postmating and premating isolation. To test for postmating isolation, they looked at whether broods from crosses were successfully reared. The results below give the percentage of successful rearings for each group of crosses.
WH × WH - 75%
P1 × P1 - 95%
P2 × P2 - 80%
P1 × P2 - 77%
WH × P1 - 0%
WH × P2 - 0%

They also found statistically significant premating isolation between the WH population and the field populations. Finally, the Woods Hole population showed slightly different karyotypes from the field populations.

Just thought I'd share that.  [edit:  source:  http://www.talkorigins.org/faqs/faq-speciation.html]