Comparative study of the disjunct zonation pattern of the grey mangrove Avicennia marina (Forsk.) Vierh. in Gazi Bay (Kenya)

摘要: The disjunct zonation pattern of Avicennia marina (Forsk.) Vierh., frequently observed along the Kenyan coast as a landward and seaward zone, has been studied on morphological level complemented with preliminary genetic data. objective was to describe two zones in-depth in order provide background ecological setting that may be used explanations emergence such bimodal zonation. vegetation structure is described by means Braun-Blanquet releve PCQ-methods, root- leaf-morphological characteristics, environmental variables setting. show considerable differences physiognomy A. trees, indicate constitute an response. Results tree heights, leaf sizes, density, total length pneumatophores tend smaller compared same attributes trees zone. Differences stomatal density above- below-ground pneumatophore length, latter closely related effect inundation, were observed. This suggests adaptability plasticity respect conditions. hypothesis for analysis mangrove fringes close 105 m from one another pool. Preliminary using 48 amplified DNA fragments (RAPD - Randomly Amplified Polymorphic DNA) 37 revealed significantly different frequencies four fragments, indicating there might less contact interchange between than within each Whether this phenomenon, coupled conditions, can lead further divergence cannot answered yet. Of all patterns worldwide various authors, Vierh. provides incentive particular because its nature (Watson, 1928; Macnae, 1968, 1969; Johnstone, 1983; Smith, 1987a, 1992). In Kenya species displays across intertidal zone (Dahdouh-Guebas et al., 2002). present most well fringe forest at certain locations coast. reported other specific regions world; however, it visually or superficially without intensive sampling comparisons. Walter Steiner (1936) higher tidal “exceptions” specimens. Other authors (e.g., 1968; 1992) “double zonation” marina, but did not go beyond stating observation mentioning personal observations height size varies upper lower zones. paper more rigorous comparison (such height, size, root etc.), framing We also findings differentiation Rather aiming generalization