Gut content analysis and a new feeding group classification of termites

1. Gut content analysis of termites was undertaken using microscopical tech niques. The 46 study species covered the entire range of taxonomic and feed ing forms within the Order. 2. Inter-specific gut contents data were analysed using principal component s analysis. placing species along a clear humification gradient based on va riations in the amount of silica and plant tissue fragments in the gut. 3. Redundancy analysis was used to find morphological correlates of the obs erved variation in gut contents. A total of 22 morphological characters (ou t of 45 candidate characters) were correlated significantly with the gut co ntents. 4. Three of the 22 significantly correlated characters unambiguously define d feeding groups, which were designated groups I to IV in increasing order of humification of the feeding substrate. Group I contains lower termite de ad wood and grass-feeders; group II contains Termitidae with a range of fee ding habits including dead wood, grass, leaf litter, and micro-epiphytes; g roup III contains Termitidae feeding in the organic rich upper layers of th e soil; group IV contains the true soil-feeders (again all Termitidae), ing esting apparently mineral soil. These groupings were generally supported st atistically in a canonical covariance analysis, although group II apparentl y represents termite species with a rather wide range of feeding habits. 5. Using existing hypotheses of termite phylogenetic relationships, it seem s probable that group I feeders are phylogenetic ally basal, and that the o ther groupings have arisen independently on a number of occasions. Soil-fee ding (i.e. group III and group IV feeding) may have evolved due to the co-o ption of faecal material as a fungal substrate by Macrotermitinae-like ance stral forms. As a consequence, these forms would have been constrained to b uild nest structures from soil and would therefore have passed at least som e soil through their guts.