Distribution and Ecology of Marine Fungi in Sierra Leone (Tropical West Africa)

Abstract

AbstractThe distribution of marine fungi in Sierra Leone is studied in the light of hydrographic and climatic factors.Altogether 27 spp. have been identified to species level, comprising 3 Phycomycetes 14 Ascomycetes and 10 Deuteromycetes. All these spp. are considered as new records to the country and about 50 % of them are inhabitants of mangrove swamps under tidal influence.The climate of Sierra Leone is characterized by two main seasons: a wet season (May - November) and a dry season (December-April).Mangrove mycota display a seasonal periodicity, increasing in number of spp. and growth intensity in the wet . season. Degradation of wood was also active during this season, apparently more by members of Deuteromycetes such as Cirrenalia spp., Periconia prolifica and Zalerion spp. than by Ascomycetes.Sea foam was also richer in fungal ascospores (including 6 spp. of Corollospora) and conidia of Deuteromycetes in the wet than in the dry season.Estuarine foam. however. comprises several Hyphomycetes of freshwater or terrestrial origin brought in by runoff during the rainy season (e.g. Alternaria, Curvularia, Drechslera, A cro sporidium , etc.)No distinct vertical zonation was displayed by the lignicolous fungi inhabiting the mangrove.The geographical distribution of the higher marine fungi under consideration has been compared with those on the opposite side of the Atlantic as well as in the Pacific and Indian Oceans. Out of 24 spp. found in Sierra Leone, 21 spp. (88 %) occur on the opposite side of the Atlantic. while an equal number is known in the Pacific. Only 15 spp. (63 %) are recorded in the Indian Ocean. The last figure is due to our limited knowledge of Indian Ocean fungi and is expected to increase in future.The distribution of mangrove fungi encountered in Sierra Leone is considered as a "community" comprising host specific forms such as Leptosphaeria avicenniae and Cytospora rhizophorae, as well as facultative forms. Out of 14 such spp. in Sierra Leone, 13 (93 %) occur in the Western Atlantic. 12(86 %) in the Pacific and 10(72 %) in the Indian Ocean so far. The close affinities of mangrove fungi in the 3 oceans, paralleled with similar affinities of mangrove floras lend support to the theory of a common center in the West-Indo Pacific for the mangrove flora and associated mycota from which a drift took place in various directions into the 3 oceans in question. The theory was postulated by Ekman (1953) for the distribution of tropical fauna and found support by Macnae (1968) for the distribution of the mangrove flora and fauna. It also allows for an endemic element as the drift deviates from the center.The closer affinities between Eastern and Western Atlantic mycota could be explained by the current gyres to the north and south of the equator and their role in transporting mangrove seeds. wood and associated fungi between the African arid American coastlines.