The genetic control of heterochrony: Evidence from developmental mutants of Pisum sativum L.

Abstract

Heterochrony, as a means of evolution in which the rate or timing of developmental events of the descendant is altered compared with that of the ancestor, is of significance because it suggests that rapid and dramatic morphological changes are possible with few genetic changes. The putative origin of plant taxa by this means of evolution is becoming increasingly frequent in the literature but there is little evidence of the extent of the genetic change necessary to alter the timing of developmental events to produce such changes. This study shows that the onset of flowering can be altered independently from the vegetative transition in leaf form in at least one genotype of Pisum in response to different environments. Further, it identifies 9 mutations that act in a heterochronic manner to produce dramatic morphological changes that can be described as progenesis, neoteny, hypermorphosis or acceleration. In addition, it is demonstrated that the same heterochronic process (e.g. progenesis) may be caused by genes controlling distinctly different physiological processes. It is suggested that Pisum is an ideal model species for studies of heterochrony and that few genetic changes are necessary to bring about dramatic heterochronic changes. Copyright © 1994, Wiley Blackwell. All rights reserved