Background and aims – Opuntia s.s. (Cactaceae) is one of the most diverse genera, with approximately 200 species, as species have great morphological and anatomical variation, which have caused a high adaptive plasticity in the species, reflected in the intra- and interspecific variability. Our study system was Opuntia streptacantha Lem., which has two floral morphs: yellow and orange. The objective was to determine if there were morphological differences in the reproductive and vegetative structures between floral morphs.

Material and methods – Statistical tests were performed to determine if there were differences in morphological structures (8 cladodes structures (n= 20 cladodes for each floral morph) and 17 flowers structures (n= 30 flowers for each floral morph) and multivariate models of principal and discriminant components. Also, reproductive phenology was registered for both floral morphs to describe the phenophases of each (n=10 individuals for each floral morph).

Key results and conclusion – We found that floral morphs of O. streptacantha showed significant differences mostly associated with the flowers. The principal component analysis revealed seven components that explain 80% of the total variation, some individuals of O. tomentosa were classified as floral morphs of O. streptacantha, not having a clear separation between the species. The phenology of the floral morphs showed a slight lag in their peak flowering and fruiting. Very high floral synchrony was found for each floral morph and between them. The modifications found in the flowers of O. streptacantha may be associated with a possible hybridization with O. tomentosa favoring the appearance of both floral morphs.