The traditional view of terrestrial nutrient limitation has tended to focus primarily on the macronutrients, nitrogen and phosphorus, and their effects on plants and animals within terrestrial ecosystems. Experiments manipulating micronutrients have determined that when macronutrients are plentiful, micronutrients like calcium, potassium, and sodium may also be key limiting or co-limiting factors in terrestrial ecosystems. We posed the question, do microbes within host organisms respond to host nutrient limitation? We expected that microbiome diversity would decrease when no longer limited by environmental N and P. Both macro- (N and P) and micronutrients (Ca, K, and Na) were manipulated in all possible combinations (n= 70, 16 total treatments, 8 replicates, 128 plots of 30m by 30m) in a large scale fertilization experiment at a coastal tall-grass prairie in Texas. Grasshoppers were collected using sweep nets (100 sweeps/ plot). We subsequently dissected the grasshoppers and removed the gut in its entirety. The gut sample DNA was extracted and then 16s sequencing was performed to better understand the types and relative numbers of microbes in each gut sample. Statistical analysis, including Shannon and Simpson diversity, ANOVA, and NMDS determined relationships between types and numbers of microbes within the host microbiome and nutrient treatment.
Results/Conclusions
Grasshoppers collected in the experimental prairie treatment plots were responsive to certain micronutrients, especially sodium, with increased bacterial diversity, particularly through the appearance of rare groups. While male and female gut microbiomes were very similar in composition, different host trophic levels did correlate with different microbiome composition. These results support not only the idea that micronutrients can be limiting in prairie ecosystems, but that micronutrients may also affect host microbiomes.