I have two invited reviews due this summer, building on the theme from my book, that past natural selection improved trees (and the wild ancestors of our crops) much more than it has improved the overall organization of forests (and other natural ecosystems):
In Global Food Security, Andy McGuire and I will ask, "What can agriculture learn from nature?" If natural selection or some other process had consistently improved the overall organization of natural ecosystems, then agriculture might benefit from copying that organization. If every natural ecosystem had some process that adjusted the relative abundance of species to maximize ecosystem-level productivity and/or stability, then we could (for example) try to match the ratio of grasses and legumes in our pastures to those in nearby grazed meadows. I expect to argue, however, that nothing has consistently improved natural-ecosystem organization, so mindless mimicry of natural ecosystems is unlikely to improve agriculture. The wild ancestors of key crops grew naturally as monocultures, but that doesn't necessarily mean polyculture wouldn't be better. It's still worth studying how natural-ecosystem organization affects productivity and stability, and thinking about which features of natural ecosystems might be worth copying.
In "Evolutionary tradeoffs as crop-improvement opportunities", intended for Field Crops Research , I will argue that past natural selection has been improving individually-beneficial plant traits like drought tolerance for millions of years, leaving few simple, tradeoff-free options for further improvement. Accepting tradeoffs rejected by past natural selection has been key to past crop improvement and that is probably still true.
For a preview, see my discussions with farmer/blogger Chris Smaje and soybean-breeder Clem Weidenbenner in the comments for this post on Small Farm Future.
Chris argues that rotating annual crops with pasture is copying nature. I don't see any close analogs to such rotations in nature, so disagree. The pasture phase might benefit from copying some aspects of natural grazing systems, though.
Clem has various examples of plant breeding improving crops in ways that natural selection hasn't. I agree, but would any of those changes have improved individual-plant fitness in nature? If not, what are the prospects for improving traits like stress tolerance, which would (if tradeoff-free) have improved individual fitness?
Increasing or decreasing oil content beyond its natural range would presumably decrease fitness, even though it may be useful to us. Clem mentions range expansion of crops, which could show that humans can improve traits like cold tolerance in ways that past natural selection on the crop's wild ancestors didn't. I need to read more about this, but I find it interesting that high-altitude maize picked up cold-tolerance genes from teosinte, not the other way around.