HOMOLOGY AND HETEROCHRONY IN THE EVOLUTION OF CONIFER REPRODUCTION (Invited Presentation)

Homology is foundational to the study of evolution. Knowledge of evolutionary sameness is a prerequisite for studying patterns and processes in the evolution of organismal form and for developing the phylogenetic hypotheses that are fundamental to modern evolutionary biology. Among plants, the simplicity of body plans can create complex challenges for understanding homology. Vascular plant sporophytes are composed of just 4 different organ types that are modified to perform a wide range of functions: stems, leaves, roots, and sporangia. Understanding homology can thus be especially difficult when the modification involves reduction or congenital fusion of multiple organs. This is the case for the seed cones of conifers, for which two aspects of homology remain unresolved: (1) the identity of seed-bearing structures in each family, and (2) how these structures evolved from those of ancient conifers in the fossil record. In this talk I will discuss current evidence on seed cone homology based on anatomy, fossils, and developmental genetics in the context of conifer phylogeny, and explore the role of heterochrony in the evolution of these structures.