Nitrogen and carbon stable isotope ratios in the sympatric Australian termites, Amitermes laurensis and Drepanotermes rubriceps (Isoptera: Termitidae) in relation to their feeding habits and the quality of their food materials

Tissue N and C stable isotope ratios of two sympatric termite species were investigated in relation to those of their stored food materials at two savanna sites in north-eastern Australia (Woodstock and Oak Valley). At both sites, the δ15N values of termite tissues and the stored food materials of the litter-feeding species Amitermes laurensis were significantly greater than their equivalents in the grass-harvesting species Drepanotermes rubriceps. In addition, the carbohydrate/lignin and C/N ratios were higher and chitin/carbohydrate ratios were lower in food materials stored in the mounds of D. rubriceps. Both sets of analyses confirmed that D. rubriceps assimilates less decomposed food materials than A. laurensis. Tissue δ13C values indicated that both species assimilated similar proportions of C3 and C4 plant materials at the Woodstock site, but that the workers of A. laurensis assimilated a greater proportion of C3 plant material at the Oak Valley site. The δ15N values of termites from the Woodstock site were significantly greater than those from Oak Valley, although the differences in order at each site were consistent between species. The results indicate that N and C stable isotope ratios must be carefully compared across habitats.