Lignin characteristics and density fractions of termite nests in an Amazonian rain forest--indicators of termite feeding guilds?

High termite abundance and diversity in rainforests results in the creation of different termite nests, which are formed from excreted food waste. The objective of this study was to elucidate the properties of nest material of common rain forest termites by analysing residues of potential food sources. In the Amazonian rain forest near Manaus, Brazil, we sampled nests of six different termite genera as well as surrounding wood, microepiphytes and soil. After a density separation into <1.6, 1.6-1.8, 1.8-2.0, 2.0-2.4, and >2.4 g cm-3 fractions, we determined the contents of C, N, and lignin-derived phenols in the samples. As particle density increased, the element and lignin concentrations decreased in all samples, the remaining lignin showed evidence of increased side-chain oxidation (P < 0.05). The termite nests contained 7.3-22 times more C, 14-220 more lignin-derived phenols, and 5.6-260 times more light fraction material than the surrounding surface soils (0-10 cm). The nests of the wood-feeding guild contained 1.2-15 times more lignin and 1.1-46 times more light material than those of the soil/wood-interface feeders. Among the different nests, the particle density increased in the order Nasutitermes sp. < Cornitermes sp. < Termes sp. < Embiratermes sp. < Anoplotermes sp. (soil). In the same direction the content of lignin-derived phenols decreased from 111 to 3 g kg-1 nest material and amounted to 0.5 g kg-1 soil. The results indicated a shift from wood to soil material in the nests. Nests of Constrictotermes sp. had low lignin content despite high proportions of the light material. This indicated feeding on microepiphytes. We conclude that variations in lignin characteristics and density fractions of termite nests reflect differences in feeding guilds of the studied taxa.