Anatomical-foliar diversity in three species of Lupinus L. (Fabaceae) from central Mexico and its taxonomic implications

Lupinus L. comprises approximately 280 species with high diversity in the American continent. The knowledge and taxonomic delimitation of this is still scarce and inconsistent. Anatomical characters provide information for the taxonomic resolution of several plant groups, nevertheless, that is scarce for Lupinus. The objective of this study is to conduct a comparative anatomical analysis of three species of Lupinus which are morphologically well separated, investigate the structure of their leaves to evaluate the taxonomic significance of their characters for confirm their existing classifications and reveal anatomical characteristics that have not yet been reported for the group. The study utilizes leaflets and petioles from three distinct localities of L. bilineatus Benth., L. hintonii C.P. Smith and L. mexicanus Cerv. ex Lag. were collected, fixed in the field, and processed using conventional histological techniques for inclusion in paraplast and permanent preparations of cross sections and for epidermis characterization. Thirty-two qualitative and twenty-five quantitative characters were examined. The latter were based on statistical analyses. The histological structure of the leaflet and petiole are described. The statistical analysis showed that some characters distinguish the species, as the abundance, location, and length of adaxial stomata, the thickness of the anticlinal wall, the height of adaxial epidermal cells, the type and density of trichomes, the height of adaxial papillae, the type of mesophyll, the magnitude of the midrib, diameter of vessels in middle in the leaflet. The outline and height of epidermal cells, type and number of collenchyma strata, arrangement and number of vascular bundles and location of air spaces in the petiole. The combination of qualitative and quantitative traits indicates a high degree of similarity within the species, particularly between the populations of L. hintonii. Eleven characters differentiates the L. mexicanus population Lm3 from the other two, suggesting that it is a distinct species.