Quantifying relative contributions of biotic interactions to bacterial diversity and community assembly by using community characteristics of microbial eukaryotes

Abstract

Biotic interactions are known as a major control on microbial diversity. However, biotic interactions have rarely been quantified in an adequate manner, often leaving much residual variation unexplained in microbial biogeographic studies. Herein, we propose a holistic approach to disentangle the relative importance of inter-domain interactions in shaping microbial diversity by incorporating community-level characteristics. Taking coastal bacterioplankton on a regional scale as an example, we designated a range of community characteristics of pico- and nanoeukaryotes derived from metabarcoding and flow cytometric data as inter-domain interacting proxies, which were then considered in statistical modeling. We found that the bacterial diversity indices and community structure were much more accurately explained by a number of eukaryotic characteristics than by the measured environmental variables and/or spatial variables alone, as were the richness, relative abundances, and assemblage structures of major bacterial taxa. In co-occurrence networks, the nodes of characteristics that had more edges (links) were frequently the best explanatory variables for bacterial diversity indices. Over 70% of total variation in bacterial community structure could be explained by three categories of biotic interactions: parasitism (27%), fungi-bacterial competition (32%), and trophic structure and bacterivory (13%). This study showcases a methodological framework to infer different types of inter-domain interactions at play, and stresses the importance of non-grazing interacting processes in shaping bacterial diversity and community assembly.

Keywords

• Community assembly
• Environmental selection
• Microbial biogeography
• Microbial interaction
• Stochasticity