How complex microbial communities respond to climatic fluctuations remains an open question. Due to their relatively short generation times and high functional diversity, microbial populations harbor great potential to respond as a community through a combination of strain-level phenotypic plasticity, adaptation, and species sorting. However, the relative importance of these mechanisms remains unclear. We conducted a laboratory experiment to investigate the degree to which bacterial communities can respond to changes in environmental temperature through a combination of phenotypic plasticity and species sorting alone. We grew replicate soil communities from a single location at six temperatures between 4°C and 50°C. We found that phylogenetically- and functionally-distinct communities emerge at each of these temperatures, with K-strategist taxa favoured under cooler conditions, and r-strategist taxa under warmer conditions. We show that this dynamic emergence of distinct communities across a wide range of temperatures (in essence, community-level adaptation), is driven by the resuscitation of latent functional diversity: the parent community harbors multiple strains pre-adapted to different temperatures that are able to "switch on" at their preferred temperature without immigration or adaptation. Our findings suggest that microbial community function in nature is likely to respond rapidly to climatic temperature fluctuations through shifts in species composition by resuscitation of latent functional diversity.

Bacterial isolates were collected from a species sorting experiment. Isolates were grown at different temperatures, their growth, respiration and ATP content measured in order to produce thermal performance curves for these traits. Please see the accompanying published article: Smith, T.P., Mobrikotb, S., Ransome, E., Kontopoulos, D-G., Pawar, S., Bell, T. 2022. Latent functional diversity may accelerate microbial community responses to temperature fluctuations. eLife. Accepted.

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