Phylogenetic analysis of methanogen partial 16S rRNA sequences from yak and cattle clone library inferred using MEGA (ver. 5). Of the 414 clones examined, 209 clones from yak and 205 clones from cattle were assigned to 95 OTUs by MOTHUR using a 98% species level identity. These 95 OTUs are shown by representative sequences on the tree. In which, 16 OTUs from non-TALC group are presented in Figure1a, and 79 OTUs from TALC group are presented in Figure1b. GenBank accession number are indicated in parentheses and bootstrap values (>50%) from 1000 replications are indicated on the tree.The scale bar corresponds to 2 changes per 100 positions.