Ecological Scaling of Temporal Fluctuations with Bacterial Abundance in Gut Microbiota Depends on Functional Properties of Individual Microbial Species and Bacterial Communities.

Macroecological relationships that describe various statistical associations between species' abundances, their spatial, and temporal variability are among the most general laws in ecology and biology. One of the most commonly observed relationships is a power-law scaling between means and variances of temporal species abundances, known in ecology as Taylor's law. Taylor's law has been observed across many ecosystems, from diverse plant and animal ecosystems to complex microbial communities. While many mathematical models have been proposed to explain the potential origins of Taylor's law, what determines its scaling exponents across species and ecosystems is not understood. Here, we use temporal trajectories of human and baboon gut microbiota to analyze the relationship between functional properties of individual bacterial species and microbial communities with the scaling of species-specific and community-level Taylor's law. The species Taylor law characterizes - for each individual species - the relationship between the species' temporal abundance means and temporal abundance variances across host organisms. On the other hand, community-level Taylor's law characterizes - in each host organism - the scaling across multiple species between their temporal abundance means and temporal abundance variances. For community Taylor's law, we find that the power law scaling is strongly associated with the microbiota abundance of certain nutrient-degrading enzymes in the gut. Notably, our results demonstrate that the availability of enzymes metabolizing starch glycogen significantly increases Taylor's law scaling. We also find that species Taylor's law depends on the individual species' functional properties. Specifically, we observe lower Taylor's law scaling for species with larger metabolic networks, for species that are able to grow on a larger number of carbon sources, and for species with particular metabolic functions, such as glutamine and folate metabolism. Overall, our study reveals that Taylor's law scaling is strongly associated with the functional capabilities of bacterial communities and individual microbial species' biosynthetic properties, which are likely related to their ecological roles in the gut microbiota.