Plant Evolution and the Reciprocity Model

Abstract

This paper is a mathematical elaboration of a structural-chemical reciprocity model depicting the evolution of an organic system as an oscillation between morphological and biosynthetic adaptive impasses. A restatement of the model is made in terms of catastrophy theory, where the controlling parameters are defined by (1) DNA information storage modes (i.e., D₁ and D₂), (2) mutation rates for DNA-base and proteinamino acid substitutions, based on Eigen's phenomenological rate equations, and (3) plasticity fitness surfaces. It is speculated that plants, as opposed to animals, have stored more DNA information in D₁ (i.e., have depended on a greater divergence from the equi-probability of a uniform base composition), which would allow for a greater tolerance to neutral base (and concomitant amino acid) substitutions resulting in a greater plasticity under selected environmental variates. Trends in Silurian-Devonian plant evolution are re-stated in terms of the models proposed, and related to the bryophytic ‘optimal design.’