Telomes, theory change, and the evolution of vascular plants

Abstract

Evolutionary theory has been dominated by the so-called “modern synthesis” since its inception in the 1930's. Zimmermann's telome theory incorporates the same gradualistic assumptions as the modern synthesis and has nurtured and molded thought patterns of paleobotanists and students of plant evolution. Telome theory, like the modern synthesis, should not be faulted for what it includes so much as for what it excludes. Telome theory emphasizes evolution by terminal additions to successive ontogenies but is usually employed descriptively as if mature organs have undergone webbing, fusion, recurvation and the like. Thought patterns of this sort are necessarily gradualistic and do not recognize internal factors controlling development that might affect non-terminal stages. Interpretation of vascular plant phylogeny has been overly constrained by assumptions and mechanisms that occupy the core of the modern synthesis. Certain nongradualistic explanations for the evolution of selected organisms are reviewed and attention focused on the role of internal constraints controlling ontogenetic pathways and their macroevolutionary consequences.