Convergence of microbial community function in common environments is associated with loss of function in alternate environments

Poster Number: 
Presenter/Primary Author: 
Ashley Keiser
Michael S. Strickland
Mark A. Bradford

Soil microbial communities play a pivotal role in providing ecosystem services, given that they are key drivers of biogeochemical processes such as carbon and nitrogen cycling. As species-rich communities, made-up of populations with short generation times, it is commonly assumed that there is a high degree of functional redundancy within soil communities with respect to broad-physiological processes, such as organic carbon decomposition. This assumption underlies the majority of terrestrial ecosystem models, where relationships between processes and controlling factors are parameterized using statistical relationships generated from measurements across space. However, microbial communities display biogeographic patterns, even at fine scales. New work shows that these biogeographic patterns extend to microbial community function, with functioning influenced by differences in resource histories. We examined whether a common resource history might cause functionally dissimilar communities to converge functionally. Next, we tested whether functional convergence (partial or complete) is associated with a reduction in function in alternate environments (a functional ‘trade-off’). We used a 6 x 2 (soil community inoculum x litter environment) full-factorial design under controlled, laboratory conditions. Cumulative CO2-C values in the initial 100-day run, for inocula in both grass and hardwood litter environments, were widely divergent. This indicated that the initial inocula were functionally distinct. Differences in cumulative CO2-C values decreased among inocula in the second and third runs. The increasing similarity in cumulative CO2-C values among inocula, observed in the successive 100-day runs, is consistent with functional convergence of communities exposed to a common environment. Cumulative CO2-C values in the alternate environments were approximately half those observed for communities inoculated into the same environment. Our results suggest that distinct microbial communities can converge functionally when exposed to a common environment, and that convergence is associated with loss of function in alternate environments.

Student Poster: 
Contest Result: 
3rd Honorable Mention