Institute of Resource Assessment

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Browsing Institute of Resource Assessment by Subject "AFLP"

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    Crossing Barriers in an Extremely Fragmented System: Two Case Studies in the Afro-Alpine Sky Island Flora
    (2014) Wondimu, Tigist; Gizaw, Abel; Tusiime, Felly M.; Masao, Catherine A.; Abdi, Ahmed A.; Gussarova, Galina; Popp, Magnus; Nemomissa, Sileshi; Brochmann, Christian
    The flora on the afro-alpine sky islands is renowned for extreme fragmentation, representing a unique natural experiment in biogeography. Here we address the roles of isolation and gene flow, in particular across the narrow Rift Valley (the RV barrier) that cuts through the Ethiopian Highlands (EH), and across the vast low-lying landscape that separates EH from the East African mountains (the EH–EA barrier). We inferred the history of two species with different dispersal mechanisms, but with similar geographic ranges and habitats based on Amplified fragment length polymorphisms (AFLPs). Contrary to our predictions, we found that the populations from opposite sides of the RV barrier were less similar than those from opposite sides of the EH–EA barrier, and that only the supposedly short distance-dispersed species (Trifolium cryptopodium) showed a strong signal of secondary gene flow across the RV barrier. In the wind-dispersed Carduus schimperi, we rather found an evidence for the gene flow between differentiated populations inhabiting different EA mountains. Both species harbored little genetic diversity but considerable genetic rarity in several individual mountains, suggesting long-term isolation and bottlenecks during climatically unfavorable periods. Our genetic data corroborate a division of C. schimperi into three subspecies, but with new delimitation of their ranges, and of T. cryptopodium into two intraspecific taxa. Our findings support the idea that stochasticity may play a major role in shaping extremely fragmented ecosystems such as the afro-alpine. After initial colonization of different mountains, periods of isolation may alternate with unpredictable episodes of intermountain gene flow.
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    Phylogeographic History and Taxonomy of Some Afro-Alpine Grasses Assessed Based On Aflps and Morphometry: Deschampsia Cespitosa, D. Angusta and Koeleria Capensis
    (Springer Link, 2013-10) Masao, Catherine A.; Gizaw, Abel; Piñeiro, Rosalía; Tusiime, Felly M.; Wondimu, Tigist; Abdi, Ahmed A.; Popp, Magnus; Gussarova, Galina; Lye, Kåre A.; Munishi, Pantaleo; Nemomissa, Sileshi; Brochmann, Christian
    Phylogeographic studies in the high mountains of Africa are hampered by the limited material available, resulting in insufficient knowledge of taxonomic variation within and among closely related species. Here, we address genetic and morphological variation in three grass species, of which one (Deschampsia angusta) has been reported as narrowly endemic and vulnerable whereas Deschampsia cespitosa and Koeleria capensis are widely distributed also outside the afro-alpine region. We used amplified fragment length polymorphisms (AFLPs) to assess genetic structuring and diversity in material collected during recent field expeditions and included additional herbarium material in morphometric analyses. The plants identified as the endemic D. angusta were genetically very similar to those identified as D. cespitosa from the same mountain (Mt Ruwenzori), forming a single coherent genetic group in STRUCTURE analysis. The plants identified as D. angusta seem to represent extremes of continuous gradients of morphological variation within a single, variable species, D. cespitosa. We found that the afro-alpine material of Deschampsia consists of three genetically very distinct groups corresponding to the three mountains investigated, suggesting persistence in isolated afro-alpine refugia during one or more glacial cycles. In contrast, we found no clear genetic structure in K. capensis. This species harbored very little genetic diversity in all six mountain areas examined, and little genetic rarity except in the Ethiopian Simen Mts. This pattern may be explained by recent colonization of the afro-alpine region from a single source population or possibly by extensive recent gene flow combined with bottlenecks. We found, however, some differentiation between different K. capensis populations from Mt Kilimanjaro, corresponding to two described varieties. This study demonstrates the need for further taxonomic exploration of the enigmatic flora of the isolated afro-alpine ‘sky islands’ and highlights that different species may have conspicuously different phylogeographic histories.