Intraspecific variation in morphological and defensive traits of guava genotypes and their implications for herbivory

Introduction Intraspecific genotypic variation arising from artificial selection can shift how plants allocate resources, often unbalancing traits related to growth, reproduction, and defense. Such trade-offs may increase susceptibility to herbivory, particularly in genotypes subjected to strong selection. While perennial plants often retain ancestral traits, the effects of selective breeding on their morphological and chemical characteristics—and their consequences for plant–herbivore interactions—remain poorly understood. Here, we examined how intraspecific genotypic variation shaped by artificial selection influences morphological and biochemical traits in guava ( Psidium guajava ), and how these traits affect herbivory. Methods We evaluated seven guava genotypes, two wild, two landraces, and three cultivated to capture genetic variation using material from a germplasm bank in Zacatecas, Mexico. We measured tree, leaf, and fruit morphology; total soluble solids (°Brix); water content; and total phenolic compounds in leaves and fruits. Folivory and frugivory were also quantified. Results Most traits varied significantly among genotypes. Cultivated guavas generally had larger leaves, greater fruit biomass, and heavier seeds, but lower concentrations of chemical defenses in both leaves and fruits. However, no trade-offs were detected between morphological and defensive traits. Foliar herbivory varied among genotypes but was not associated with the origin of the plant. Moreover, herbivory showed no correlation with any morphological or biochemical traits. Conclusion Although artificial selection appears to have reduced certain defensive traits in some guava genotypes, the extent to which it has shaped trait expression and herbivore resistance in wild versus cultivated populations remains unclear.