The importance of crisis progenitors in recovery from mass extinction

Progenitor taxa are defined as species or lineages which arise, commonly through punctuated or macroevolutionary processes, during the main phases of a mass extinction interval, and which then survive to seed the evolution of diminant groups during ensuing radiation and ecosystem recovery. Their success in surviving the servere environmental perturbations commonly associated with mass extinctions and their immediate aftermath lies in the fact that they are initially adapted in their evolution to these dynamically changing environments. This differentiates them from other surviving clades of ecological generalists, opportunists, disaster taxa, taxa with speicalized survival machanisms, etc., all of which may have a long pre-extinction evolutionary history. Progenitor taxa characterize those ecosystems which are most severely affected by mass extinction processes (perturbations and feedback loops), e.g. those of tropical to warm temperate climate zones. Progenitor taxa are rarer in those ecosystems with relatively minor response to environmental perturbations of mass extinction intervals (deep sea and more poleward areas), where many established perextinction lineages survive the extinction event(s) with little change. In several published records of 'explosive radiation' among new lineages following mass extinctions, high-resolution stratigraphic sampling has shown that many of these 'new' recovery taxa actually had their origins as small, relatively rare progenitor taxa during the preceding mass extinction intervals. Examples from Cretaceous mass extinction intervals are presented (Cenomanin-Turonian, Cretaceous-Tertiary).