Leaf-based characterization of intermediate forms between Cuban and Honduran mahogany

The genus Swietenia includes two mahogany species, Swietenia macrophylla (King.), commonly known as Honduran mahogany, and Swietenia mahagoni (L.) Jacq, commonly known as Cuban mahogany. There are reports of morphologically intermediate forms between Cuban and Honduran mahogany that have been localized in some Caribbean islands. The main objective of this research is to distinguish morphologically intermediate forms between the parental species S. mahagoni and S. macrophylla based on leaf morphological characters. Phenotypic data from a total of 357 mahogany trees were collected in the province of Sancti Spiritus, Cuba. Rachis length, petiole length, leaflet length, leaflet width, number of leaflets and number of nerves were evaluated. Morphological descriptor analysis revealed significant differences in the morphometric variables of the evaluated leaves, with rachis length, number of leaflets, leaflet length, petiole length, leaflet width, and number of nerves being significantly higher in S. macrophylla than in S. mahagoni. ANOVA reflected the variance between all leaf morphological parameters evaluated between the two pure species with statistically significant difference. Using the function obtained in the first DC of the two species, the individuals in the mixed stands were classified into 71 morphologically intermediate forms, 45 S. macrophylla and 64 S. mahagoni. In the second DC with the two species and the morphologically intermediate forms, Wilks’ partial lambda indicates that the variable "leaflet length" with 0.67 contributed most to the overall discrimination.