Dispersal biophysics and adaptive significance of dimorphic diaspores in the annual Aethionema arabicum (Brassicaceae)

•Heteromorphic diaspores (fruits and seeds) are an adaptive bet-hedging strategy to cope with spatio-temporally variable environments, particularly to fluctuations in favourable temperatures and to unpredictable precipitation regimes in arid climates.
•We conducted comparative analyses of the biophysical and ecophysiological properties of the two distinct diaspores (mucilaginous seed [M+] vs. indehiscent [IND] fruit) in the dimorphic annual Aethionema arabicum (Brassicaceae), linking fruit biomechanics, dispersal aerodynamics, pericarp-imposed dormancy, diaspore abscisic acid (ABA) content, and phenotypic plasticity of dimorphic diaspore production to its natural habitat and climate.
•Two very contrasting dispersal mechanisms of the Ae. arabicum dimorphic diaspores were revealed. Dehiscence of large fruits leads to the release of M+ seed diaspores, which adhere to substrata via seed coat mucilage, thereby preventing dispersal (anti-telechory). IND fruit diaspores (containing non-mucilaginous seeds) disperse by wind or water currents, promoting dispersal (telechory) over a longer range.
•The pericarp properties confer enhanced dispersal ability and degree of dormancy to the IND fruit morph to support telechory, while the M+ seed morph supports anti-telechory. Combined with the phenotypic plasticity to produce more IND fruit diaspores in colder temperatures, this constitutes a bet-hedging survival strategy to magnify the prevalence in response to selection pressures acting over hilly terrain.