Linking temperature dependence in fitness effects of mutations to thermal niche adaptation

Fitness effects of mutations may generally depend on temperature that influences all rate-limiting biophysical and biochemical processes.  Earlier studies suggested that high temperatures may increase the availability of beneficial mutations (“more beneficial mutations”), or allow beneficial mutations to show stronger fitness effects (“stronger beneficial mutation effects”).  The “more beneficial mutations” scenario would inevitably be associated with increased proportion of conditionally beneficial mutations at higher temperatures.  This in turn predicts that populations in warm environments show faster evolutionary adaptation but suffer fitness loss when faced with cold conditions, and those evolving in cold environments become thermal-niche generalists (“hotter is narrower”).  Under the “stronger beneficial mutation effects” scenario, populations evolving in warm environments would show faster adaptation without fitness costs in cold environments, leading to a “hotter is (universally..., Data collected from an experimental evolution project. 
 
Eighteen Escherichia coli evolution lines and 18 Pseudomonas fluorescens evolution lines evolved at three temperatures as isolated cultures.  Nine incubators were used in this study, randomly assigned into three blocks.  The three incubators in each block were set 19, 26 or 31°C.  There were two replicate microcosms for each species in every incubator.  Therefore, a total of 18 evolution lines were established for each species (3 blocks × 3 temperatures × 2 within-incubator replicates). 
 
Population density was measured as colony formation units per ml.
 
Fitness of each evolved population against it ancestral strain at each of the three temperatures (19, 26 or 31°C) was measured by competition experiment.  Fitness of evolved E. coli populations and their ancestor, all of the strain REL606, relative to a reference strain, REL606Ara+, was measured by head-to-head competition assays.  Fitness of evolved and ancestral P. fluorescen..., , # Title of Dataset: Linking temperature dependence of fitness effects of mutations to thermal niche adaptation

## Description of the data and file structure

There are three data files.

The \"Density data\" file (cvs table) shows the mean population densities (log-transformed) over time of each evolution line during the selection experiment. Nine incubators were used in this study, randomly assigned into three blocks (A, B and C). The three incubators in each block were set 19, 26 or 31°C. There were two replicate microcosms for each species in every incubator. Variable \"block\" indicate which block an evolution line belong to; variable \"evolution.temperature\" indicates at which temperature the evolution lines are selected; variable \"replicate\" indicates the within-incubator replicate ID. Species \"E\" represents Escherichia coli and P, Pseudomonas fluorescens. Densities were measured as colony formation units per ml.

The \"Fitness data\" file (cvs table) gives fitness assayed in home and a...