Pulsing hydrology and topography determine the structure and spatial distribution of Cubitermes mounds in a savanna ecosystem

Spatial patterns are important to understanding factors that shape many ecological processes in natural plant and animal communities. However, the spatial patterns of Cubitermes mounds remain poorly understood despite their importance in many ecological processes in savanna ecosystems. We assessed the structural characteristics and spatial patterns of Cubitermes mounds in 25 × 25 m plots along a catena sequence i.e. upper, middle and bottom in a seasonal savanna wetland. A density of 1317 mounds ha− 1 was estimated for this savanna system. Mound density decreased whereas mound size increased down the catena, and mounds were absent in the floor region of the catena due to prolonged inundation. Spatial analysis showed that mounds were randomly distributed in the upper section of the catena and either random or clustered in the middle and bottom sections. True segregation between large and small mounds only occurred in the upper section of the catena; otherwise small mounds were either randomly distributed or clustered in relation to large mounds in the middle and bottom sections of the catena. With increase in spatial scale, however, mounds were independent indicating the absence of interaction between mounds. In the bottom region of the catena, mounds were independent at small spatial scales but positively correlated with increase in spatial scales a result consistent with low mound density and mutual stimulation, respectively. In conclusion, along the catena sequence, mound size and spatial distribution are a function of competition in the upper regions, whereas in the bottom regions these characteristics appear to be regulated by inundation. The study highlights the importance of hydrology, topography and competition for the structure and spatial patterning of Cubitermes mounds, and consequently for the spatial heterogeneity of ecological processes in savanna ecosystems.