Browsing by Author "Meimberg, Harald"

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    Anthropogenic impacts on the contextual morphological diversification and adaptation of Nile tilapia (Oreochromis niloticus, L. 1758) in East Africa
    (Environmental Biology of Fishes, 2018) Dias Tibihika, Papius; Waidbacher, Herwig; Masembe, Charles; Curto, Manuel; Sabatino, Stephen; Alemayehu, Esayas; Meulenbroek, Paul; Akoll, Peter; Meimberg, Harald
    Nile tilapia occurs naturally in East Africa where it’s an economically important species. Many of the natural populations of Nile tilapia have been affected by anthropogenic activities including translocations, associated with programmes aimed at enhancing capture fisheries and aquaculture productivity. Using geometric morphometric analyses, we tested the hypothesis that such anthropogenic activities have augmented admixture among natural populations of Nile tilapia and influenced the geographical distribution of morphological variation within the species. Our expectation was that Nile tilapia shape divergent might be consistent with reportedly anthropogenic activities in nonnative environments. To test this hypothesis, we analyzed the shapes of 490 individuals from thirteen populations; three farms, six natives and four nonnative natural populations. Our analysis revealed that the most pronounced shape diversification was observed in seven populations; three nonnatives (Victoria, Kyoga and Sindi farm) and four natives (Albert, River Nile, George and Turkana). The features responsible for the observed morphotypes were mainly related to the orientation of the anterior region of the fish and may be due to diversifying selection in response to new environmental pressures (for nonnative populations), admixture or drift. Shape change in the nonnative high-altitude populations was unexpectedly conserved, suggesting recent introductions which may have not resulted in admixture or there was strong selection against change in the traits measured. On the other hand, the recorded morphotypic clusters explained the possible genetic link to their putative ancestral home. Our results were partially consistent with our prediction that the nonnative populations exhibited divergent morphotypes. We recommend further investigations with molecular genetics for followup of these findings.
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    Knowledge Gaps in Taxonomy, Ecology, Population Distribution Drivers and Genetic Diversity of African Sandalwood (Osyris lanceolata Hochst. & Steud.): A Scoping Review for Conservation
    (plants, 2021) Mugula, Ben Belden; Kuria Kiboi, Samuel; Ireri Kanya, James; Egeru, Anthony; Okullo, Paul; Curto, Manuel; Meimberg, Harald
    The increasing demand for ornamental, cosmetic and pharmaceutical products is driving exploitation of plant species globally. Sub-Saharan Africa harbours unique and valuable plant resources and is now a target of plant resource depletion. African Sandalwood (Osyris lanceolata), a multi-purpose and drought-tolerant species, has seen increased exploitation for the last thirty years and is now declared endangered. Initiatives to conserve O. lanceolata are not yet successful in Africa due to poor understanding of the species. This review surveys relevant research on the ecology, taxonomy, population dynamics, genetic diversity and ethnobotany of O. lanceolata, and highlights gaps in the literature for further research. A scoping review of grey literature, scholarly papers and reports was applied with pre-determined criteria to screen relevant information. Review findings indicate O. lanceolata is a globally distributed species with no identified center of origin. In Africa, it ranges from Algeria to Ethiopia and south to South Africa; in Europe it occurs in the Iberian Peninsula and Balearic Islands; in Asia from India to China, and also on Socotra. The species has a confusing taxonomy, with unresolved issues in nomenclature, country range distribution, extensive synonymisation and variation in growth form (shrub or tree). The species population is reported to be declining in Africa, but information on population dynamics across its entire range of distribution is anecdotal. Additionally, ecological factors influencing spatial distribution and survival of the species remain unknown. A variety of uses are reported for O. lanceolata globally, including: cultural; medicinal and food; dye; perfumery; timber; ethnoveterinary and phytoremediation. Key research areas and implications for conservation of O. lanceolata in Sub-Saharan Africa are proposed.
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    Molecular genetic diversity and differentiation of Nile tilapia (Oreochromis niloticus, L. 1758) in East African natural and stocked populations
    (BMC Evolutionary Biology, 2020) Tibihika, Papius Dias; Curto, Manuel; Alemayehu, Esayas; Waidbacher, Herwig; Masembe, Charles; Akoll, Peter; Meimberg, Harald
    The need for enhancing the productivity of fisheries in Africa triggered the introduction of non-native fish, causing dramatic changes to local species. In East Africa, the extensive translocation of Nile tilapia (Oreochromis niloticus) is one of the major factors in this respect. Using 40 microsatellite loci with SSR-GBS techniques, we amplified a total of 664 individuals to investigate the genetic structure of O. niloticus from East Africa in comparison to Ethiopian and Burkina Faso populations. Results: All three African regions were characterized by independent gene-pools, however, the Ethiopian population from Lake Tana was genetically more divergent (Fst = 2.1) than expected suggesting that it might be a different sub-species. In East Africa, the genetic structure was congruent with both geographical location and anthropogenic activities (Isolation By Distance for East Africa, R2 = 0.67 and Uganda, R2 = 0.24). O. niloticus from Lake Turkana (Kenya) was isolated, while in Uganda, despite populations being rather similar to each other, two main natural catchments were able to be defined. We show that these two groups contributed to the gene-pool of different non-native populations. Moreover, admixture and possible hybridization with other tilapiine species may have contributed to the genetic divergence found in some populations such as Lake Victoria. We detected other factors that might be affecting Nile tilapia genetic variation. For example, most of the populations have gone through a reduction in genetic diversity, which can be a consequence of bottleneck (G-W, < 0.5) caused by overfishing, genetic erosion due to fragmentation or founder effect resulting from stocking activities. Conclusions: The anthropogenic activities particularly in the East African O. niloticus translocations, promoted artificial admixture among Nile Tilapia populations. Translocations may also have triggered hybridization with the native congenerics, which needs to be further studied. These events may contribute to outbreeding depression and hence compromising the sustainability of the species in the region.