Effects of patch connectivity and heterogeneity on metacommunity structure of planktonic bacteria and viruses

Abstract

Dispersal limitation is generally considered to have little influence on the spatial structure of biodiversity in microbial metacommunities. This notion derives mainly from the analysis of spatial patterns in the field, but experimental tests of dispersal limitation using natural communities are rare for prokaryotes and, to our knowledge, non-existent for viruses. We studied the effects of dispersal intensity (three levels) and patch heterogeneity (two levels) on the structure of replicate experimental metacommunities of bacteria and viruses using outdoor mesocosms with plankton communities from natural ponds and lakes. Low levels of dispersal resulted in a decrease in the compositional differences (beta diversity) among the communities of both bacteria and viruses, but we found no effects of patch heterogeneity. The reductions in beta diversity are unlikely to be a result of mass effects and only partly explained by indirect dispersal-mediated interactions with phytoplankton and zooplankton. Our results suggest that even a very limited exchange among local communities can alter the trajectory of bacterial and viral communities at small temporal and spatial scales.

Effects of dispersal and selection on stochastic assembly in microbial communities

“…Thus, we find that low dispersal rates in natural decomposer communities might result in apparently weak deterministic effects (low significance of environmental effect) that would have been apparent with higher dispersal rates. Supporting this idea, Lindström and Östman (2011) also found that deterministic effects in lakes only become apparent when bacterial dispersal reached intermediate rates (but see Declerck et al, 2013, where this occurs at a much lower dispersal rate). Notably, when we grouped taxa into functional groups according to their traits and performed the same community analyses, communities grouped more strongly by their local environment (data not shown), suggesting in Figure 3 Nonmetric multidimensional scaling ordinations showing simulated communities after 6 years of sorting on substrates with low lignin/N (orange, lignin/N = 20.1, 30.2, 48.6) that are low in quality and induce strong selection, or substrate with low lignin/N (blue, lignin/N = 3.9, 7.8, 12.9) that are high in quality and induce weaker selection.…”

Advection shapes Southern Ocean microbial assemblages independent of distance and environment effects

“…As it is possible that an unmeasured environmental variable (for example, iron concentration; microenvironmental factors owing to particle attachment) also correlates with both advection and community composition, future studies should address this. Mesocosm experiments 17 may also help to address the effects of small-scale exchanges of cells on community structure.…”

“…Indeed, advection is often invoked to explain observations of microbial diversity or abundance, which do not seem attributable to environmental selection (for example, refs [13][14][15][16]. The exchange of very small volumes of water between marine microbial mesocosms has been found to greatly reduce their b-diversity (in this case, compositional differences between communities from different mesocosms) even under consistent environmental conditions 17 . This suggests that advection of even small numbers of cells could have a large homogenizing effect independent of environmental selection.…”

Spatially cascading effect of perturbations in experimental meta-ecosystems

“…Experimentally, much lower dispersal rates (less than 0.01%) have been shown to significantly affect metacommunity dynamics (e.g. [30]). …”