No, they haven't.
"Increasingly, they have been forced to tack ad hoc mechanisms onto Darwin’s theory to accomodate (sic) the evidence."
No, they haven't.
Evolution as the origin of species hasn't been defeated.
Natural selection as the driving force of evolution hasn't been defeated either.
As more information comes in from the fields of geology, paleontology, and biology, the mechanisms of speciation become clearer, but the basic theory hasn't been challenged in any factual, logical way. Besides, "evidence" is a non-count noun. I think the writer meant examples or research.
Man, are you so very wrong.
Evolution is just as big a scientific scam as AGW. The only difference is that its believers never found a way to tie it to political policies that aim to destroy civilization and, oh by the way, massively redistribute wealth.