Persistent inner tepals and wings protect developing seeds of <i>Rheum nanum</i> from insect herbivory in Central Asian cold deserts

Although the postdispersal functions of diaspore (fruit and its appendages) have been reported, little is known about their protective/defensive functions. In this context, diaspores with appendages (persistent inner tepals and/or fruit wings) that experienced predispersal herbivory by insects in natural populations of <i>Rheum nanum</i> were investigated, and the seed abortion percentage, seed and embryo masses, and germination of seeds from diaspores with different categories of insect herbivory were measured and compared. Predispersal insect herbivory of <i>R</i>. <i>nanum</i> diaspores was prevalent in the four investigated populations, but the percentage of diaspores with appendages (persistent inner tepals and and/or fruit wings) damaged by insects was significantly higher than that of diaspores with the pericarp damaged by insects. Seeds from diaspores with gnawed appendages experienced significantly less damage than those with gnawed pericarps. Importantly, we conclude that fruit appendages of <i>R</i>. <i>nanum</i> help to mechanically protect developing seeds from predispersal insect herbivory.