Institute of Resource Assessment

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Browsing Institute of Resource Assessment by Subject "Afro-alpine"

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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.
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    Vicariance, Dispersal, and Hybridization in a Naturally Fragmented System: The Afro-Alpine Endemics Carex Monostachya and C. Runssoroensis (Cyperaceae)
    (Springer Link, 2016) Gizaw, Abel; Wondimu, Tigist; Mugizi, Tusiime F.; Masao, Catherine A.; Abdi, Ahmed A.; Popp, Magnus; Ehrich, Dorothee; Nemomissa, Sileshi; Brochmann, Christian
    The naturally fragmented habitat on the tallest African mountains provides a good model system to study vicariance, dispersal, and hybridization. Many mountains are separated by lowland that likely was unsuitable for high-alpine plants even during cold climatic periods. We explore the relative importance of these processes using two endemic sister species: the widespread Ethiopian/eastern East African Carex monostachya and the mainly western East African C. runssoroensis. These bog-forming sedges co-occur in some mountains and are hypothesized to hybridize. The two species were distinctly differentiated for genome-wide amplified fragment length polymorphisms (AFLPs), also in one mountain where they co-occur. However, the plants from another mountain showed strong signals of admixture. The results suggest initial divergence into one western and one northern/eastern lineage, followed by long-distance dispersal resulting in secondary contact zones. In addition within species genetic diversity was clearly structured with distinct genetic groups on some, but not all mountains. Differentiation levels varied considerably and did not always correspond to the extent of lowland habitat between mountains. The narrow Rift Valley in the otherwise nearly contiguous highlands in Ethiopia appears to present a much stronger barrier to dispersal than the extensive lowlands separating Ethiopia from East Africa. This may be a general pattern since it has been documented also for other afro-alpine species.