GO TO A LIBRARY. He is not citing to "obscure" journals but to journals you should be able to find on the shelves just about anywhere. Evolution happens by small steps. After a hundred speciations, the resemblance to the original is meager. Sometimes, giving sterile hybrids however. But there is a recorded case of a speciation through interbreeding of cabbage and turnip (also in the Brassicaceae family I think): the fertilized ovum went through a polyploidy (copying all the chromosomes without splitting the cell) so that each descendant cell had two copies of all the cabbage chromosomes and two of all the turnip chromosomes, and thus the new plant could breed with itself, but not with either cabbage or turnip. Unfortunately this species has a root like a cabbage and foliage like a turnip!