Browsing by Author "Wondimu, Tigist"

Now showing 1 - 1 of 1
  • No Thumbnail Available
    Item
    History of Plant Colonization, Speciation and Genetic Diversity in the Afro-Alpine Environment: Evidence From Molecular Data
    (Addis Ababa University, 2011-07) Wondimu, Tigist; Nemomissa, Sileshi (Professor); Brochmann, Christian (Professor)
    Recent phylogenetic and phylogeographic studies of some afro-alpine plants suggested repeated long-distance migrations of plants into Africa mainly from Eurasia. Such repeated migrations may have played an important role in the plant species composition of the isolated afro-alpine 'sky island' flora. The current study used African Swertia spp., Trifolium cryptopodium, Geranium arabicum, a putative new species of Geranium, Carduus schimperi and Umbilicus botryoides to assess the history of plant colonization and speciation in the high mountains of Ethiopia and East Africa (Kenya, Tanzania and Uganda). The African species of Swertia were used in phylogenetic and biogeographic analyses while the remaining species were used to explore phylogeographic history and the level of their genetic diversity across the afro-alpine environment of Eastern Africa. Sequences of two non-coding plastid regions [the trnL-F region (both the intron and the intergenic spacer)] and the trnS-fM intergenic spacer, one coding plastid region (matK) and the nuclear ribosomal internal transcribed spacer (ITS) were used to investigate the phylogenetic relationships, biogeography and divergence time of African Swertia. The African species formed two distantly related clades, each closely related to different Himalayan species of the genus. Thus, this study revealed two episodes of colonization of Africa by different lineages of Swertia from the Himalayas. Molecular divergence data analysis of these taxa indicated that the earliest migration of Swertia into Africa took place in the Miocene Epoch. In the phylogeographic studies of the other taxa, two or three primer combinations were selected for AFLP analysis. The phylogeographic analyses of the AFLP data indicated several long-distance migrations among the high mountains in Ethiopia and East Africa. In two species, Carduus schimperi and Trifolium cryptopodium, the populations from Bale Mountains in Ethiopia were genetically more similar to populations from the East African Mountains than to those from other Ethiopian mountains. The putative new species of Geranium (listed as Geranium sp. nov. = G. S. Miehe 3002 in Flora of Ethiopia and Eritrea as endemic to the Bale Mountains) was not found to be genetically distinct from the widespread and genetically variable G. arabicum, suggesting that the characters used to distinguish it merely represent phenotypical plasticity. In contrast, the previous division of Carduus schimperi into three subspecies based on morphology was supported by the genetic data, except that the material from the Bale Mountains which previously had been referred subsp. schimperi grouped with the East African subsp. nanus. Key words: Afro-alpine flora, AFLP, Biogeography, Divergence time, In situ radiation, Phylogeny, Phylogeography, matK, trnL-F, trnS-fM, ITS.