Nemomissa, Sileshi (Professor)Dagne, Kifle (PhD)Bekele, Biructawit2018-06-252023-11-082018-06-252023-11-082006-05http://etd.aau.edu.et/handle/123456789/3367Swertia abyssinica (Hochst.) S. lugardae (Bullock) and S. pumila (Hochst.) (Gentianaceae) are closely related taxa occurring in the high mountains of North East Africa. Amplified Fragment Length Polymorphism (AFLP) markers were used to assess the genetic variation between the higher and the lower altitude populations of the taxa within and between different mountain regions. In a principal coordinate analysis (PCoA), the resulted grouping of accessions of the first two taxa corresponds with their geographical locations rather than taxonomic classifications while S. pumila was far and distinct. Such groupings were inconsistent with previous study based on morphology. The PCoA result was supported by the AMOVA with higher variations among mountains (21.4 %) than variations within mountain among taxa (14.5 %). The considerable reduction in variation among taxa (7.03 %) in the AMOVA excluding S. pumila and its distinct position in the PCoA implies S. pumila as a different taxon. The evolutionary distance tree based on AFLP characters supported the results from AMOVA and PCoA. These results are in contradiction with the acceptance of three distinct species, but rather suggest as two distinct species. Thus the results suggest clinal morphological differences between the two, S. abyssinica and S. lugardae. Thus it is likely that the clinal variation is caused by primary cline than hybridization. Although there was non - significant variation between altitudes and weak correlation between them, it is difficult to conclude for the absence of genetic base for the clinal morphological variation. Key words: Swertia, ecoclinal evolution, genetic diversity, glacial refugia, AFLPenSwertiaecoclinal evolutiongenetic diversityglacial refugiaAFLPThesis