Nutritional and defensive properties of Fagaceae nuts dispersed by animals: a multiple species study

Seeds usually exhibit physical and chemical defensive properties; however, it is still debated whether there is trade-off between the two defensive traits. Moreover, the relationship between nutritional and defensive properties of seeds is rarely investigated. In this study, we measured chemical compositions and physical properties of 29 species/varieties in Fagaceae with different seed traits, to investigate variations in nutritional and defensive properties at interspecific level. Our study provided evident nutritional trade-off in Fagaceae nuts, i.e., the concentration of protein and fat was negatively correlated with that of starch. However, no clear trade-off between physical and chemical defensive traits was found, indicating coordinated defense syndromes in these Fagaceae species. Chemical defense in Fagaceae nuts was positively associated with fat and protein but negatively with the content of starch. The congruence between phylogenetic tree and seed trait cladogram indicated conservative evolution of seed traits. In addition, large nuts had high concentration of protein and fat, resulting in a positive relationship between seed coat thickness and caloric values. Fagaceae nuts with high nutrition tended to invest more energy into physical defenses, indicating that the trade-off between chemical and physical defenses might be seed size dependent across plant species.