The evolution of reproductive structures in seed plants: a re-examination based on insights from developmental genetics

Contents Summary 910 I. Introduction 910 II. Transformation and transference in angiosperm developmental genetics 911 III. Implications for understanding patterns of seed plant evolution 916 IV. Understanding the origin of the flower 919 V. Conclusions 920 Acknowledgements 921 References 921 Summary The study of developmental genetics is providing insights into how plant morphology can and does evolve, and into the fundamental nature of specific organs. This new understanding has the potential to revise significantly the way we think about seed plant evolution, especially with regard to reproductive structures. Here, we have sought to take a step in bridging the divide between genetic data and critical fields such as paleobotany and systematics. We discuss the evidence for several evolutionarily important interpretations, including the possibility that ovules represent meristematic axes with their own type of lateral determinate organs (integuments) and a model that considers carpels as analogs of complex leaves. In addition, we highlight the aspects of reproductive development that are likely to be highly labile and homoplastic, factors that have major implications for the understanding of seed plant relationships. Although these hypotheses may suggest that some long-standing interpretations are misleading, they also open up whole new avenues for comparative study and suggest concrete best practices for evolutionary analyses of development.