Transferring concepts from plant to microbial ecology: A framework proposal to identify relevant bacterial functional traits

In the past decade, there was a growing interest in using functional trait approaches to study soil bacterial communities. However, microbial ecology as lagged behind plant and animal ecology in implementing such an approach. One of the main difficulties is linked to the absence of a small set of well identified bacterial functional traits, relevant for defining ecological strategies, explaining community assembly and predicting community impact on ecosystem functioning. Taking inspiration from plant functional ecology, we propose that functional traits should not be identified based on their relationship to an ecosystem function of interest, but rather on their relationship to bacterial fitness. We propose a framework in which bacterial fitness is composed of three components: growth rate, survival and dispersion. We identify putative functional traits linked to those components, in particular 16S rDNA copy number for growth rate. We propose several ways of validating identified functional traits by observing changes in community-aggregated trait values along environmental gradients, observing relationships between relative abundance and trait values within communities and comparing community and regional pool traits diversity. Finally, we argue for using traits to define bacterial ecological strategies and identify relationships between response and effect traits.