Spatial and temporal variation in distribution of Gelidium canariensis (Rhodophyta) from natural populations of the Canary Islands

This study was designed to investigate spatial and temporal variation in Ge lidium canariensis populations at two shores in northern Gran Canaria durin g two years. Spatial scales ranged from some hundred meters (distance betwe en shores), 10 to 30 m (distance between pilots) to less than 3 m (distance between quadrats). Gelidium individuals were defined as distinct Gelidium clumps. The results show a significant difference in size of clumps between shores, but not on the smaller spatial scales. No significant temporal var iation was found. There was no significant temporal or spatial variation in standing crop or density (counts made in quadrats where Gelidium was prese nt, rather than counts for the total shore). Sporophytic and gametophytic c lumps were also distinguished by identifying reproductive structures in the field. The total proportion of sporophytes was larger than the proportion of gametophytes, but at a smaller scale there could be a shift in dominance . The survival rate of clumps was similar between shores with a mean surviv al rate of 85%, but there eras a significant difference in recruitment betw een shores. The results indicate a stable population structure.