Fig. 7

Passive and active trends may occur simultaneously at different scales. In a, there is a driven trend at the global scale (note the increasing global minimum), although in each component lineage, the trend is passive (note that in each case variance increases but the minimum does not). In b, there is a passive trend at the global scale (because of an expansion in variance with a limit at the low end), even though within each component lineage the trend is driven (because the driven trends at local scales occur in both directions). Based on McShea (2001)