The reality of higher taxa and the question of intermediate forms.

Abstract

Emphasis is placed on the fact that forms intermediate between closely related species of diverse genera are well known, that there are far fewer such examples between closely related genera, and almost none between families and higher taxa. The simplest explanation is that species to species level links, evolved in a microevolutionary manner, between families and higher taxa, occur under conditions of very small population size, high endemicity, and very rapidly, i.e., quantum evolution. The nature of community evolution indicates that most species level transitional forms will occur within ecological-evolutionary units, whereas almost none will occur during the adaptive radiations characterizing the initial phase of many ecological-evolutionary units. The phyletic evolution so characteristic of community evolution is gradualistic in those cases where an environmentally uniform set of samples is available. Finally, when discussing intermediate taxa it is important to state at what taxonomic level, i.e., is the form intermediate al tbe specific, generic, familial or ordinal level.