Metatranscriptomic data reveal the effect of different community properties on multifunctional redundancy

The assessment of functional redundancy (FR) is essential to understand community structure-function relationships because FR buffers the functional performance of communities against changes in community composition. We introduce a novel metatranscriptome-based approach to quantify FR, which permits multifunctional aspects to be addressed. FR among prokaryotes was ranked in water samples after exposure to changing salinity. FR was higher for functional categories with mostly broad functions shared among many taxa than for functional categories containing many narrow functions. Furthermore, community characteristics had a higher impact on FR than environmental conditions. The metric also allows FR to be estimated between selected groups of taxa, and FR was high between more closely related organisms if communities were grown in similar environmental conditions. Overall, our data revealed a pronounced influence of functional diversity on the one hand but also the characteristics of individual community members on FR, which was specifically high in those communities whose members were more sensitive to salinity changes.