Cryptic niche differentiation in West African savannah termites as indicated by stable isotopes

Termites consume a wide range of plant material at different stages of decomposition and, accordingly, have been classified into ‘feeding groups’. African savannah ecosystems harbour many termite species, yet most belong to Termitidae. Especially striking is the co‐occurrence of up to eight Macrotermitinae and five Trinervitermes species, each having apparently identical trophic niches, i.e. fungus‐growers and grass‐feeders, respectively. 2. This study examined stable isotope signatures of 15 N and 13 C of West African savannah termites to test the validity of existing feeding group concepts and whether there is fine‐scaled niche differentiation of species within feeding groups. Despite a phylogenetic signal that species from the same subfamily and congenerics have correlated isotope signatures, evidence of niche differentiation was found. 3. Interestingly, species with similar δ 15 N values generally differed in δ 13 C values, and vice versa. The dominant mound‐building fungus‐grower Macrotermes bellicosus had the lowest δ 15 N values among all fungus‐growers, indicating that it occupies a different trophic niche. 4. This fine‐scaled differentiation along the trophic niche axis can help to explain the coexistence of so many apparently identical termite species.