Comparison of Three Sympatric Desert Lizards: Digestive Tract Structure, Digestive Enzyme Activities, Gut Microbiota, and Metabolites

The flexibility of digestive tract morphology and the composition of gut microbiota play crucial roles in the environmental adaptation of reptiles. To evaluate the contributions of the dietary niches to the gut microbiota, we performed 16S rDNA sequencing and metabolite profiling for three sympatric lizard species-Teratoscincus roborowskii, Phrynocephalus axillaris, and Eremias roborowskii-and compared their goblet cell and enzyme activities of the digestive tract. The results revealed that goblet cell densities in the stomach body and pylorus were significantly higher in both T. roborowskii and E. roborowskii, which occasionally include fruit in their diets. Lipase activity was significantly higher in the insectivorous P. axillaris, while the α-amylase and cellulase activities were elevated in the omnivorous T. roborowskii and E. roborowskii. All three lizard species shared the same dominant microbiota at the phylum level. However, dietary niche differences led to P. axillaris having a higher abundance of Desulfovibrionaceae, while E. roborowskii had a significantly higher abundance of Bacteroidetes. Metabolomic profiling revealed that the metabolites involved in carbohydrate metabolism were highly upregulated in E. roborowskii, corresponding to the host's diet and metabolic pathways. Notably, a strong correlation was observed between digestive enzymes, gut microbiota, and fecal metabolites. Overall, our study suggests that the dietary niche may promote divergence or convergence of microbiota across host species, facilitating the establishment of host-specific intestinal adaptation strategies. Our findings provide insights into lizard adaptation to extreme deserts from the perspectives of the gut microbiome and digestive physiology.