Biotic processes in a coastal dunefield: An assessment of seed removal, with non-native seed removal experiments

The impact of granivores on coastal dune seed reserves may be high, increasing along a landward gradient from the littoral zone as the structural complexity of the habitat increases. Seasonal removal rates of non-native seeds by nocturnal and diurnal vertebrates and ants from experimental seed trays in two habitats within the Alexandria Coastal Dunefield, South Africa, were determined. Overall, seed removal was higher in the dune-field bush-pocket habitat than the landward thicket habitat. Nocturnal vertebrates were the most important seed removers within bush-pockets. The importance of nocturnal vertebrates decreased in the thicket and there was a shift in the dominant seed removers to diurnal vertebrates. Seed removal by ants and diurnal vertebrates did not differ significantly between the bush-pockets and thicket while that of nocturnal vertebrates showed a significant change. This can be ascribed to the abundance of the omnivorous murid rodent Gerbillurus paeba exilis in the bush-pockets which is absent from thicket vegetation.