The role of development in plant phylogeny: A paleobotanical perspective

Abstract

This paper explores the potential role of developmental changes in the macroevolution of vascular plants. The discussion is focused on an explanation of the concept of heterochrony, on factors that render it compatible with and/or supplementary to classical neo-Darwinian evolutionary theory, on the plausibility that it has had a significant evolutionary role, and on procedures for recognizing the occurrence of heterochrony from the fossil record of vascular plants. The ovulate stalks of Ginkgo biloba and growth architecture in Streptocarpus demonstrate that major structural variations can occur among closely-related individuals as the result of divergent developmental pathways. The possibility that the Coniferales had a heterochronic origin is explored as an example of how evolutionary hypotheses may be formulated from the fossil record of plants. Indirect tests utilizing the methodology of phylogenetic systematics also are included.