Abstract
Flows of water, soil, litter, and anthropogenic materials in and around rivers lead to the mixing of their resident microbial communities and subsequently to a resultant community distinct from its precursors. Consideration of these events through a new conceptual lens, namely, community coalescence, could provide a means of integrating physical, environmental, and ecological mechanisms to predict microbial community assembly patterns better in these habitats. Here, we review field studies of microbial communities in riverine habitats where environmental mixing regularly occurs, interpret some of these studies within the community coalescence framework and posit novel hypotheses and insights that may be gained in riverine microbial ecology through the application of this concept. Particularly in the face of a changing climate and rivers under increasing anthropogenic pressures, knowledge about the factors governing microbial community assembly is essential to forecast and/or respond to changes in ecosystem function. Additionally, there is the potential for microbial ecology studies in rivers to become a driver of theory development: riverine systems are ideal for coalescence studies because regular and predictable environmental mixing occurs. Data appropriate for testing community coalescence theory could be collected with minimal alteration to existing study designs.
Highlights
Lotic ecosystems hold some of the richest biodiversity on the globe (Tockner & Stanford, 2002; Dudgeon et al, 2006; Vorosmarty et al, 2010)
Community coalescence asks the same question as metacommunity theory while taking a metaecosystem perspective [what environmental flows and subsidies are occurring in this system?] to understand how, where, and when entire habitat patches, and their associated microbial communities will collide and what resulting environment and community might arise (Fig. 1). It is in line with theoretical work (Logue et al, 2011) that has called for an integration of meta-ecosystem dynamics into metacommunity studies
Microbial community coalescence occurs along the length of the river, across the terrestrial–aquatic interface from upslope soils to headwaters and downstream to estuaries
Summary
Lotic ecosystems hold some of the richest biodiversity on the globe (Tockner & Stanford, 2002; Dudgeon et al, 2006; Vorosmarty et al, 2010). Community coalescence asks the same question as metacommunity theory (how do local communities assemble given fluxes of community members across the landscape?) while taking a metaecosystem perspective [what environmental flows and subsidies (sensu Polis, Anderson, & Holt, 1997) are occurring in this system?] to understand how, where, and when entire habitat patches, and their associated microbial communities will collide and what resulting environment and community might arise (Fig. 1) It is in line with theoretical work (Logue et al, 2011) that has called for an integration of meta-ecosystem dynamics into metacommunity studies. It is noteworthy that few fungal studies met the criteria to make inferences about community coalescence (Fig. 2), and that a sixth of the 79 studies met these criteria and provided evidence for community coalescence (Fig. 3)
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