Are fungus-growing termites super sediment-sorting insects of subtropical environments?

Résumé 0

Fungus-growing termites have long been considered as ecosystem engineers for the modifications they make to the soil, through their ability to concentrate nutrients and create patches of fertile land. However, few studies have highlighted the degree to which, in building their mounds, they are able to modify the grain-size distributions of the sediments and soils in their surroundings. Therefore, the aim of this study is to document the potential impact of fungus-growing termites on sediment sorting of their environment. The assessment is based on comparisons between two different mounds and their associated control soils developed in contrasting grain-size settings, one on sand and the other on fine material (diatomite). The sedimentary modifications carried out by termites between these two parent materials and associated constructed mounds are addressed using techniques mostly based on grain-size distributions (performed with End-Member Mixing Analyses) and soil micromorphology. In order to conduct this investigation, two fungus-growing termites’ mounds were selected in the Chobe Enclave District, northern Botswana. The key questions of this study center on the capacity of fungus-growing termites to (i) adapt to any kind of parent material to build their mounds, and (ii) enrich or deplete this parent soil to meet their texture requirements in terms of mound stability and other mechanical properties to insure the success of the colony. This study demonstrated that fungus-growing termites assemble the mandatory texture required for the functions and properties of their mounds, whatever a given parent material, by selecting, transporting, and mixing the various grain sizes. To conclude, the sorting by fungus-growing termites must be considered when reconstructing paleoenvironment based on particle-size distributions.