Phenotypic characterization of the Rwandan stinging nettle (Urtica massaica Mildbr.) with emphasis on leaf morphological differences. Authors : Nduwamungu, J.1, Munyandamutsa, P.1, Senyanzobe, J.M.V.1, Ruhimbana, C.1, Ugirabe, M.A1, Mahoro, J1., Dusingize, M.C1., Kabarungi, M.1, Irimaso, E.1, Maniraho, E1., Nsabimana, P.1, Mugunga, C.1, and Mugemangango, C.2 1. College of Agriculture, Animal Sciences and Veterinary Medicine 2. College of Sciences and Technology. Corresponding author: [email protected] Abstract Patterns of intraspecific variation based on environmental conditions in which populations live may reflect adaptive responses to their habitat. The Rwandan stinging nettle plant grows in most parts of Rwanda both in the wild and domestication forms. While the plant can easily be identified through its leaves and life form, it has been observed that the leaf morphology slightly varied from one region to another. This study aimed to investigate morphological variations, particularly in leaf morphology of the Rwandan stinging nettle growing in the lowland, midland, and highland. Specimens of the stinging nettle were taken from different sites located in the three altitudinal zones. Plant heights and leaf lengths varied from one site to another and the statistical analysis revealed that the average plant heights, as well as leaf lengths of mature stinging nettle samples from highland, midland, and lowland, were significantly different. The results showed that there were morphological differences, particularly in leaves among the three altitudinal zones. The most prominent difference was in the main vein of the stinging nettle. Changes in leaf morphology can be linked to differences in environment and nutrient availability between the three habitats which could have enabled the species to evolve differently. However, the genetic basis of these phenotypic changes needs to be examined in future research to establish their heritability for future populations of the stinging nettle plant in Rwanda. Key words: Morphometrics, stinging nettle, traits, habitat, Rwanda.