From the CD-ROM "Concepts and strategies"
Biochemist James Lovelock writes of this embrace, "The evolution of a species is inseparable from the evolution of its environment. The two processes are tightly coupled as a single indivisible process."
This quote is included in Chapter 5 of Kevin Kelly's book "Out of Control", where he discusses coevolution. Kevin Kelly , like most people who discuss coevolution, tend to treat the landscape as a constant. This limits the discussion of coevolution to the interactions of living organisms and ignores the influence of changes to the landscape in which they are located.
The introduction of stigmergy allows the landscape to be brought into consideration, where it is just as much a part of the coevolutionary phenomenon as the organisms that live in it.
An interesting paper, that sees genes and memes coevolving together with a landscape consisting of the evolving human brain, has many parallels with a stigmergic system (On meme-gene coevolution by Bull, Holland and Blackmore)
Autopoiesis and Coevolution by Chris Lucas is also worth reading.