So I've found myself referring in an answer once again to the idea that complexity (insofar as it's a quantity for which "number of genes" is a proxy) has an upper bound, limited by Muller's ratchet-related processes. The idea being that if harmful mutations happen faster than natural selection can cull them, the genome will accumulate harmful mutations and the organisms' fitness will degrade over time; and that this imposes an upper bound on the size of a functional genome, because the number of harmful mutations that can happen obviously depends on the size of the functional genome (i.e. how many bases there are where a mutation would likely be harmful).
I knew about Muller's Ratchet, and when referring to it I usually refer to the Wikipedia page for it. But I first came across the concept that this defined an upper bound on complexity (as opposed to being a huge paradox of evolution and a plausible reason for sexual reproduction) in this Less Wrong post (it might have been edited since I first read it).
I've pretty much adopted this concept as a thing that happens; it makes sense to me, and I have seen other references to such an upper bound limited by mutation rates from biologists, for example most recently in this talk by Nick Lane (at 39:15).
However whenever I talk about this in discussions or debates and look for sources I cannot find an easy-to-link source that presents this argument, as seen from within the field of biology. The Wikipedia page on Muller's ratchet only talks about it in the context of asexual reproduction and LessWrong isn't a biology source. The post claims that George Williams makes this argument in his book Adaptation and Natural Selection, and that may also be what Nick Lane is referring to in the video, but a book is hard to refer to online and I would expect such a powerful concept to have more material about it anyway.
Is this concept actually the consensus in the field of biology, or evolutionary biology failing that? Either way, where can I find good, preferably linkable, sources explaining the concept or debating it if it isn't the consensus?