The Effect of Immigration on the Adaptation of Microbial Communities to Warming

Abstract

Theory predicts that immigration can either enhance or impair the rate at which species and whole communities adapt to environmental change, depending on the traits of genotypes and species in the source pool relative to local conditions. These responses in turn will determine how well whole communities function in changing environments. We tested the effects of immigration and experimental warming on microbial communities during an 81 day field experiment. The effects of immigration depended on the warming treatment. In warmed communities immigration was detrimental to community growth whereas in ambient communities it was beneficial. This result is explained if colonists came from a local species pool pre-adapted to ambient conditions. Loss of metabolic diversity, however, was buffered by immigration in both environments. Communities showed increasing local adaptation to temperature conditions during the experiment and this was independent of whether or not they received immigration. Genotypes that comprised the communities were not locally adapted, however, indicating that community local adaptation can be independent of adaptation of component genotypes. Our results are consistent with a greater role for species interactions rather than adaptation of constituent species in determining local adaptation of whole communities, and confirm that immigration can either enhance or impair community responses to environmental change depending on the environmental context.3

Historical climate controls soil respiration responses to current soil moisture

“…We postulated that microbial dispersal would reduce legacy effects under a changing moisture regime (16). To separate historical and current climate conditions in the field, we transplanted soil cores from the wetter eastern and drier western regions of the rain gradient into common gardens located in each region.…”

“…For 12 mo, microcosms were incubated at 24°C in the dark and moisture treatments maintained within ±1% via weekly weighing. To measure CO 2 flux from soils, air samples were collected from the headspace of each microcosm at the initial setup and 1, 2, 3, 4,6,8,12,16,20,24, and 52 wk after the start of the incubation experiment.…”

Evidence for microbial local adaptation in nature

“…In a study conducted by Lawrence et al . (), community local adaptation was directly contrasted with the adaptation of individual isolates. While whole communities were found to be locally adapted, their respective isolates showed no such patterns, indicating that local adaptation may differ widely across levels of analysis.…”

Enhanced biofilm formation aids adaptation to extreme warming and environmental instability in the diatom Thalassiosira pseudonana and its associated bacteria

“…This could be particularly important in the fluctuating environment, where the bacteria may experience the ‘short’ fluctuations as considerably longer than do the diatoms, thus being selected in a fairly different environment than the environment the eukaryote is experiencing. Although the taxonomic composition remained relatively stable throughout selection, it is possible that the function of individual species has changed on evolutionary time scales (Lawrence et al , ). While we cannot answer this question with the data presented here, future studies might aim to look into functional rather than taxonomic diversity, or selectively knock out bacterial functions via gene‐editing tools, such as CRISPR‐Cas mediated gene regulation.…”

“…This may limit our ability to predict tempo, mode, and consequences of microbial evolution in a warming ocean. While theoretical frameworks exists to predict thermal responses of metabolism and growth (Angilletta et al 2003;Kingsolver et al 2004; Huey 2008), we may not be able to use these to directly predict the way that even simple assemblages of microbes adapt to warming (Lawrence et al 2016). Interactions within genotypes of the same species or between different species can range from cross-feeding, facilitated horizontal gene transfer, and intraspecific competition to cheating, division of labor, or cooperation (Poltak and Cooper 2010;Madsen et al 2012;Pekkonen et al 2013;Alsterberg et al 2017;Lowery et al 2017).…”