SPATIAL USE OF AN EQUATORIAL COASTAL SYSTEM (EAST-AFRICA) BY AN ARTHROPOD COMMUNITY IN RELATION TO PERIODICALLY VARYING ENVIRONMENTAL-CONDITIONS

During the dry season (1971) and the wet season (1973) two field studi es were conducted at Sar Uanle, a locality along the coast of Somalia (East Africa). The study analysed the beach-dune system considering ec ological aspects in a dynamic way. During the two periods of study and for an entire synodic period, a system of traps (directional pitfall traps) was used. At the same time the climatic factors were registered . For the most abundant arthropod species mean zonations were calculat ed during surface activity and considered in relation to the season, d iel, synodic and tidal phases. The variations in mean zonation were th en correlated with the main environmental parameters. During the wet s eason, for some taxa orientation indices were calculated. The results indicate that two distinct subcommunities are present at Sar Uanle: a more dynamic one on the beach and another on the dune. Arthropod speci es living in this beach-dune system have evolved behavioural strategie s in relation to cyclical environmental changes according to their phy siological needs, locomotory capacities and zonation. (C) 1998 Academi c Press.