Adaptation to fluctuations in temperature by nine species of bacteria

Abstract

Rapid environmental fluctuations are ubiquitous in the wild, yet majority of experimental studies mostly consider effects of slow fluctuations on organism. To test the evolutionary consequences of fast fluctuations, we conducted nine independent experimental evolution experiments with bacteria. Experimental conditions were same for all species, and we allowed them to evolve either in fluctuating temperature alternating rapidly between 20°C and 40°C or at constant 30°C temperature. After experimental evolution, we tested the performance of the clones in both rapid fluctuation and in constant environments (20°C, 30°C and 40°C). Results from experiments on these nine species were combined meta‐analytically. We found that overall the clones evolved in the fluctuating environment had evolved better efficiency in tolerating fluctuations (i.e., they had higher yield in fluctuating conditions) than the clones evolved in the constant environment. However, we did not find any evidence that fluctuation‐adapted clones would have evolved better tolerance to any measured constant environments (20°C, 30°C, and 40°C). Our results back up recent empirical findings reporting that it is hard to predict adaptations to fast fluctuations using tolerance curves.

Surfing on the seascape: Adaptation in a changing environment

“…In a recent study of multiple species of bacteria, Saarinen et al. () found that the clones evolved in the fluctuating environment were more tolerant to environmental fluctuations than the clones evolved in the constant environment. Studies of antibiotic resistance also suggest that less frequent, but stronger antibiotic treatments are more likely to cause the local extinction of the bacterial population (Wu et al.…”

“…For instance, Ketola et al (2013) observed that strains of bacterial pathogen Serratia marcescens that evolved in fluctuating temperature outperformed in novel environment the strains that evolved in constant temperature. In a recent study of multiple species of bacteria, Saarinen et al (2018) found that the clones evolved in the fluctuating environment were more tolerant to environmental fluctuations than the clones evolved in the constant environment. Studies of antibiotic resistance also suggest that less frequent, but stronger antibiotic treatments are more likely to cause the local extinction of the bacterial population (Wu et al 2014) In a frequently changing environment, similarity of threats affects the level of adaptation When the environment changes frequently relative to the time scale defined by the mutation rate (comparably to the expected time needed to get mutation at a particular locus), there is no time for populations to adapt to the current threat.…”

Fluctuating thermal environments and time‐dependent effects on fruit fly egg‐hatching performance

“…Insights about the suitability of a thermal landscape for a given species should consider not only average thermal values but also variability in thermal values (Bozinovic, Medina, Alruiz, Cavieres, & Sabat, ; Bozinovic, Sabat, Rezende, & Canals, ; Estay, Lima, & Bozinovic, ). Theoretical (Katz, Brush, & Parlange, ) and empirical studies (Easterling et al., ) have demonstrated that daily and seasonal variation in temperature affects organisms’ ecology and fitness (Clavijo‐Baquet et al., ; Gilbert & Miles, ; Kielland, Bech, & Einum, ; Messenger & Flitters, ; Roitberg & Mangel, ; Saarinen, Laakso, Lindström, & Ketola, ). In addition, thermal extremes, defined as events that alter the distribution of ambient temperature without influencing the mean and the variance (Ummenhofer & Meehl, ), have also been shown to have outstanding effects on physiological performance and survival (Bozinovic, Medina, et al., ; Kingsolver & Woods, ).…”

When enemies do not become friends: Experimental evolution of heat-stress adaptation in a vertically transmitted parasite

“…A straightforward explanation for these observations is adaptation of Caedibacter to high-temperature stress, just like it is observed in experiments with free-living bacteria 345 (Bennett et al 1992;Saarinen et al 2018), where adaptation of growth rate occurs over similar time spans. Increased heat resistance may therefore allow Caedibacter to attain viable 15 within-host densities, track the regular dilution, when host cells divide, and thereby achieve a high fidelity and rate of vertical transmission.…”