Understanding how plants cope with changing habitats is a timely and important topic in plant research. Phenotypic plasticity describes the capability of a genotype to produce different phenotypes when exposed to different environmental conditions. In contrast, the constant production of a set of distinct phenotypes by one genotype mediates bet hedging, a strategy that reduces the temporal variance in fitness at the expense of a lowered arithmetic mean fitness. Both phenomena are thought to represent important adaptation strategies to unstable environments. However, little is known about the underlying mechanisms of these phenomena, partly due to the lack of suitable model systems. We used phylogenetic and comparative analyses of fruit and seed anatomy, biomechanics, physiology, and environmental responses to study fruit and seed heteromorphism, a typical morphological basis of a bet-hedging strategy of plants, in the annual Brassicaceae species Aethionema arabicum Our results indicate that heteromorphism evolved twice within the Aethionemeae, including once for the monophyletic annual Aethionema clade. The dimorphism of Ae. arabicum is associated with several anatomic, biomechanical, gene expression, and physiological differences between the fruit and seed morphs. However, fruit ratios and numbers change in response to different environmental conditions. Therefore, the life-history strategy of Ae. arabicum appears to be a blend of bet hedging and plasticity. Together with the available genomic resources, our results pave the way to use this species in future studies intended to unravel the molecular control of heteromorphism and plasticity.

Biosystematics Group Wageningen University 6708 PB Wageningen The Netherlands ; and

Department of Biology Botany University of Osnabrück 49076 Osnabrueck Germany

Department of Biology Botany University of Osnabrück 49076 Osnabrueck Germany ;

Department of Biology Science Faculty Gazi University 06500 Teknikokullar Ankara Turkey

Department of Biology Science Faculty Gazi University 06500 Teknikokullar Ankara Turkey ;

Department of Botany Faculty of Science Hacettepe University 06800 Beytepe Ankara Turkey

Department of Botany Faculty of Science Hacettepe University 06800 Beytepe Ankara Turkey ;

Department of Genetics Friedrich Schiller University 07743 Jena Germany

Department of Genetics Friedrich Schiller University 07743 Jena Germany ;

Department of Physiology Faculty of Medicine Mersin University 33343 Mersin Turkey

Department of Physiology Faculty of Medicine Mersin University 33343 Mersin Turkey ;

Gregor Mendel Institute of Molecular Plant Biology Austrian Academy of Sciences Vienna Biocenter 1030 Vienna Austria

Gregor Mendel Institute of Molecular Plant Biology Austrian Academy of Sciences Vienna Biocenter 1030 Vienna Austria ;

Laboratory of Growth Regulators Centre of the Region Haná for Biotechnological and Agricultural Research Palacký University and Institute of Experimental Botany Academy of Sciences of the Czech Republic 78371 Olomouc Czech Republic

Plant Cell Biology Faculty of Biology University of Marburg 35043 Marburg Germany

Plant Cell Biology Faculty of Biology University of Marburg 35043 Marburg Germany ;

School of Biological Sciences Plant Molecular Science and Centre for Systems and Synthetic Biology Royal Holloway University of London Egham Surrey TW20 0EX United Kingdom

School of Biological Sciences Plant Molecular Science and Centre for Systems and Synthetic Biology Royal Holloway University of London Egham Surrey TW20 0EX United Kingdom ;

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