Microenvironment

What was seen from the top down, as a large environment with many difficult trade-offs, is instead seen from the bottom up--as 10 million microenvironments, each to be regulated in its own right. It is this inversion of perspective that distinguishes microgovernment from other kinds of regulation, and that accounts for its often-bizarre behavior.

Source: wiktionary

As with the Lejeuneaceae, this pattern of massive speciation appears to be correlated with the Cretaceous explosion of the angiosperms and the simultaneous creation of a host of new microenvironments, differing in humidity, light intensity, texture, etc.

Source: wiktionary