The evolutionary ecology of clonally propagated domesticated plants

Abstract

Summary: While seed‐propagated crops have contributed many evolutionary insights, evolutionary biologists have often neglected clonally propagated crops. We argue that widespread notions about their evolution under domestication are oversimplified, and that they offer rich material for evolutionary studies. The diversity of their wild ancestors, the diverse ecologies of the crop populations themselves, and the intricate mix of selection pressures, acting not only on the parts harvested but also on the parts used by humans to make clonal propagules, result in complex and diverse evolutionary trajectories under domestication. We examine why farmers propagate some plants clonally, and discuss the evolutionary dynamics of sexual reproduction in clonal crops. We explore how their mixed clonal/sexual reproductive systems function, based on the sole example studied in detail, cassava ( Manihot esculenta ). Biotechnology is now expanding the number of clonal crops, continuing the 10 000‐yr‐old trend to increase crop yields by propagating elite genotypes. In an era of rapid global change, it is more important than ever to understand how the adaptive potential of clonal crops can be maintained. A key component of strategies for preserving this adaptive potential is the maintenance of mixed clonal/sexual systems, which can be achieved by encouraging and valuing farmer knowledge about the sexual reproductive biology of their clonal crops. Contents Summary 318 I. Domesticated plants as model systems in evolutionary biology: bringing clonally propagated crops into the fold 319 II. Advantages and disadvantages of clonal propagation 319 III. Evolution in clonal populations: somatic mutations and epigenetic traits as sources of heritable variation 321 IV. Evolutionary dynamics of sex in clonally propagated crop plants 323 V. Mixed clonal‐sexual systems: how do they work? 325 VI. Domestication syndromes in clonally propagated crops 327 VII. The future of clonally propagated domesticated plants 328 Acknowledgements 329 References 329