Browsing by Author "Kebede, Mulugeta"

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    Comparative Phylogeography and Conservation Genetics of Some Afro-Montane Plant Species From Ethiopian and Tropical East African Mountains As Inferred From Aflp
    (Addis Ababa University, 2007-07) Kebede, Mulugeta; Nemomissa, Sileshi (PhD); Brochmann, Christian (Professor); Taberlet, Pierre (PhD)
    The afro-alpine region s.l. refers to the high mountains of Ethiopian and Topical East Africa. The flora of this region is unique in composition compared to the surrounding lowlands and subdivided into three altitudinal vegetation belts: the afro-montane, ericaceous and afro-alpine belts. The origin and extant distribution of the flora had been influenced strongly by the Pleistocene climatic oscillations. During glacial (cold) periods, the afro-alpine and ericaceous belts were broad while the afro-montane belt was reduced and fragmented. The montane forests had probably persisted in refugia located at mountain foothills or in river basins. Afromontane forest was extensive during interglacial (warm) periods whereas the afro-alpine and ericaceous belts were compact. Based on amplified fragment length polymorphisms (AFLPs) data, we provide insights into the origin, fragmentation and evolution of some key afromontane species in relation to Pleistocene climatic oscillations. In view of this, we focus on the genetic diversity and population genetic structure of these afro-montane plant taxa without obvious long distance dispersal morphology and that are widely distributed in the East African mountain systems (i.e., Erica arborea, Hypericum revolutum and Lobelia giberroa). Regardless of some general observed phylogeographic trends such as divergent lineages, contact zones, altitudinal shift and complex refugia, our analyses highlight that each species had a unique phylogeographic pattern and the geographical consistency of the genetic patterns differ considerably. Our observation further suggest that L. giberroa and H. revolutum genetic groups occupied geographically well defined areas while the geographic pattern of E. arboreia is rather complex. Furthermore, we have attempted to identify important areas for conservation of the current study species based on concepts of hotspots of intraspecific diversity and evolutionary significant units (ESU). This approach could be followed to assess or design appropriate genetic conservation priorities as well as a robust sampling strategiesfor further studies. This study is the first of its kind concerning the impacts of Pleistocene glaciations on the genetic structures of afro-montane/-alpine plants and it will certainly guide to scope future phylogeographic studies in Africa. In prospect, it is important to cover the whole distribution range of the study species to have more complete phylogeographic picture of the region. In addition, it is appropriate to investigate many wide-spread plant species with well-documented fossil data and use appropriate genetic criteria to deduce the impact of Pleistocene climatic fluctuations on the genetic structure of the present day afro-montane/- alpine flora. Key words: AFLP, Afro-alpine, Afro-montane, Conservation, Erica arborea, Hypericum revolutum, Lobelia giberroa, Phylogeography
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    Cytogenetic Study of Some Species of Swertia L. (Gentianaceae) from Ethiopia
    (Addis Ababa,University, 2000-05) Kebede, Mulugeta; Dagne, Kifle (PhD)
    Chromosome data have contributed little towards resolving the problems of classification and phylogeny orthe Swertia species (Y uan, 1993). For many species of the genus the chromosome number as weJ[ as morphology were not stud ied (Yuan and KUpfer, 1993). In the present work, ch romosome numbers were documented for six species of Swerlia L. (Gentianaceae) from Ethiopia. S. fimbria/a, s. kiJill/wu/s charica, S. macrosepa/a subsp. microsperma and S. va/kensii var. baleellsis were found to be diploid with 2n=26. S. crassillscula subsp. robllsta was dip loid with 211=20. The above chromosome numbers were determined from mitotic chromosomes. Diploid (211=20, n"" I 0) and tetraploid (2n=40, n=20) chromosome numbers were found for S. abyssillica from meiot ic chromosome study. The chromosome numbers of S. crassilisclila subsp. robusta , S macrosepala subsp. microsperma, S volkellsii val'. baleensis and 211=40 cytotype of S. abyssil/ica were reported for the first time. Further, the present study confimled previous reports on the chromosome numbers of the remaining species and the basic chromosome number x= 13 and x=1 0 for the genus. Karyotypes of five species of SlI'ertia namely, S fimbria/a , S. kilimalltischarica, S. macrosepala subsp. microsperma. S. crassiuscula subsp. robusta and S. volkensii val'. baleellsis have been described and their similarities and differences were discussed. Even though tile chromosome morphology of these species is very similar, some variat ions in basic number, ploidy level, satell ite number and size of chromosomes were observed among the Swerlia species studied. The study revealed that the spec ies were heterogeneous. It is recommended that fu rther study of karyotype of all the species of the genus including chromosome banding is necessary to complete the cytotaxonomic knowledge of the genus as a whole.