Mutualistic association between Num-num (Carissa bispinosa) and mounds of Snouted harvester termites (Trinervitermes trinervoides) in a semi-arid savanna
In many ecosystems, one individual, or species, may often alter the environmental conditions in such a way that a stressful habitat becomes more hospitable for other individuals. Mutualism is a relationship between two organisms of either the same species or different species that enhances their survival or growth. Mutualism drives selection for traits through evolution, leading to diversity.. However, very few of these mutual associations have been documented in the semi-arid savanna region. Due to their close association yet no report of mutualism, I studied whether there was a mutualistic association between Carissa bispinosa, a fast-growing medium sized evergreen shrub, and Trinervitermes trinervoides, a mostly nocturnal termite species, at Nylsvley Nature Reserve, Limpopo province. There was a significant benefit accrued to both species from the plant-insect association. Plants on mounds were larger, greener and fruited more in the dry season compared to stand-alone plants. Mounds under shrubs were significantly less damaged compared to exposed mounds. Certain soil macro- and micronutrients that contribute to plant growth and health were enriched in mounds relative to the matrix. Overall, internal temperature changes were fairly constant in active mounds during the 24-hour period in both seasons, while temperature changes in inactive mounds varied more. Activity and season (including their interactions), were important in determining the internal mound temperature profiles. Shade and mound size did not have any significant effect in determining the internal temperatures profiles of mounds. To my best knowledge, my study has revealed a previously undocumented survival mechanism that this species of termites uses to escape predation in semi-arid savannas.