Browsing by Author "Nyaga, Justine Muhoro"

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    Geomorphic and Climatic Drivers Are Key Determinants of Structural Variability of Mangrove Forests along the Kenyan Coast
    (MDPI, 2022-06) Njiru, Derrick Muthomi; Githaiga, Michael Njoroge; Nyaga, Justine Muhoro; Lang’at, Kipkorir Sigi; Kairo, James Gitundu
    Mangrove forests occur across a diversity of coastal landforms that influence their structural development and productivity. Preliminary studies in Kenya indicate that mangroves growing in the region north and south of Tana River delta have different structural attributes. We hypothesise a close relationship between mangrove distribution, climate and landform types. Floristic composition of mangroves along the coast of Kenya was characterised and differences illustrated using non-metric multidimensional scaling (nMDS). Other structural properties of mangroves such as tree height, basal area, stand density and standing biomass were also assessed and their differences tested using analysis of variance (ANOVA). A hierarchical cluster analysis was used to compare mangrove species based on structural properties. Additionally, a regression fit model was used to investigate the relationship between mangrove standing biomass and possible drivers of variability. The study revealed significant differences in mangrove tree diameter, tree height, basal area, stand density and standing biomass across the sampled sites. High values of structural complexity were observed in estuarine and deltaic settings with high influence of freshwater input whereas low levels of structural complexity were observed for peri-urban with direct human influence. Our findings suggest that structural variability of mangroves in Kenya is highly influenced by geomorphological and climatic variability along the coast as well as the past and present management regimes of the forest.
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    The Latitudinal Biotic Interaction Hypothesis revisited contrasting latitudinal richness gradients in actively vs. passively accumulated interaction partners of honey bees
    (UoEm, 2025) Cirtwill, Alyssa R.; Roslin, Tomas; Peña‑Aguilera, Pablo; Agboto, Agathe; Bercê, William; Bondarchuk, Svetlana N.; Brodschneider, Robert; Heidari, Behzad; Kaizirege, Camara; Nyaga, Justine Muhoro; Ojonugwa, Ekpah; Gomez, Gonzalo Ossa; Paz, Claudia; Pirk, Christian; Salehi‑Najafabadi, Amir; Salonen, Anneli; Soloniaina, Chantal; Wirta, Helena
    Contrasting hypotheses suggest that the number of biotic interactions per species couldeither increase towards the equator due to the increasing richness of potential interaction partners (Neutral theory),or decrease in the tropics due to increased biotic competition (Latitudinal Biotic Interaction Hypothesis). Empiricaltesting of these hypotheses remains limited due to practical limitations, differences in methodology, and speciesturnover across latitudes. Here, we focus on a single species with a worldwide distribution, the honey bee (Apis mellif-era L.), to assess how the number of different types of interactions vary across latitudes. Foraging honey bees interactwith many organisms in their local environment, including plants they actively select to visit and microbes that theylargely encounter passively (i.e., unintentionally and more or less randomly). Tissue pieces and spores of these organ‑isms are carried to the hive by foraging honey bees and end up preserved within honey, providing a rich recordof the species honey bees encounter in nature.