Some controversy - good to have in science: http://www.esajournals.org/doi/abs/10.1890/09-1949.1
A rebuttal commentary, nice: http://www.esajournals.org/doi/abs/10.1890/11-0063.1
Knowing what I know about top predators, I'm going with the majority opinion on this and that wolves do have far-reaching impacts through lower trophic levels. How can they not? But, you decide for yourself, the literature is free to critique.
A top predator helps another top predator? Read: http://www.sciencedaily.com/releases/2013/07/130729133120.htm.
And not just on land....http://www.sciencedaily.com/releases/2010/11/101110141533.htm