Mark Jonas

The impact of elevated carbon dioxide on plants is a growing concern in evolutionary ecology and global change biology. Characterizing patterns of phenotypic integration and multivariate plasticity to elevated carbon dioxide can provide insights into ecological and evolutionary dynamics in future human‐altered environments. Here, we examined univariate and multivariate responses to carbon enrichment in six functional traits among six European accessions ofArabidopsis thaliana. We detected phenotypic plasticity in both univariate and multivariate phenotypes, but did not find significant variation in plasticity (genotype by environment interactions) within or among accessions. Eigenvector, eigenvalue variance, and common principal components analyses showed that elevated carbon dioxide altered patterns of trait covariance, reduced the strength of phenotypic integration, and decreased population‐level differentiation in the multivariate phenotype. Our data suggest that future carbon dioxide conditions may influence evolutionary dynamics in natural populations ofA. thaliana.

A key step toward predicting responses to climate change is characterizing genetic variation in populations. While short-term responses will likely be shaped by currently available genetic variation, longer-term evolutionary responses will depend on the supply of novel variation by, ultimately, mutation. Studying mutational contributions to phenotypic variation can provide insights into the extent of potential variation on which selection may operate in future human-altered environments. Here we used the chemical mutagen ethyl methanesulfonate (EMS) to explore mutational contributions to phenotypic variation, integration, and plasticity to elevated carbon dioxide (eCO₂) in three accessions of Arabidopsis thaliana. We found that (1) mutagenesis increased broad-sense heritabilities and variation in plasticity to eCO₂ (genotype by environment interactions); (2) mutational effects varied among the three genetic backgrounds; (3) induced mutations had non-random (biased) effects on patterns of phenotypic integration. To our knowledge, this is the first study to address the effects of chemically induced mutations on phenotypic plasticity to eCO₂ in a model plant. We discuss our results in light of emerging insights from theoretical and empirical quantitative genetics, suggest potential avenues of research, and identify approaches that may help advance our understanding of climate-driven evolution in plants.

The purpose of this study was to assess the incidence of Clostridium difficile infection in patients who received rifaximin for the treatment of hepatic encephalopathy (HE). Medical charts of patients who received rifaximin for the treatment of HE were reviewed. The number of patients who developed diarrhea during treatment with rifaximin and results of latex agglutination assays to detect C. difficile in stool samples were analyzed. A total of 211 patients received rifaximin for HE. Of these, 152 were treated in a university practice and 59 were treated in community practices. The mean dose of rifaximin was 1055 mg/d (range, 600 to 1600 mg/d) for a mean duration of 250 days (range, 180 to 385 d). Eighteen patients developed diarrhea during rifaximin treatment. None of these patients tested positive for C. difficile. This study demonstrates that treatment of HE with the safe, nonsystemic, gut-selective antibiotic rifaximin was not associated with the development of C. difficile infection.