Association with pathogenic bacteria affects life-history traits and population growth in Caenorhabditis elegans.

Determining the relationship between individual life-history traits and population dynamics is an essential step to understand and predict natural selection. Model organisms that can be conveniently studied experimentally at both levels are invaluable to test the rich body of theoretical literature in this area. The nematode Caenorhabditis elegans, despite being a well-established workhorse in genetics, has only recently received attention from ecologists and evolutionary biologists, especially with respect to its association with pathogenic bacteria. In order to start filling the gap between the two areas, we conducted a series of experiments aiming at measuring life-history traits as well as population growth of C. elegans in response to three different bacterial strains: Escherichia coli OP50, Salmonella enterica Typhimurium, and Pseudomonas aeruginosa PAO1. Whereas previous studies had established that the latter two reduced the survival of nematodes feeding on them compared to E. coli OP50, we report for the first time an enhancement in reproductive success and population growth for worms feeding on S. enterica Typhimurium. Furthermore, we used an age-specific population dynamic model, parameterized using individual life-history assays, to successfully predict the growth of populations over three generations. This study paves the way for more detailed and quantitative experimental investigation of the ecology and evolution of C. elegans and the bacteria it interacts with, which could improve our understanding of the fate of opportunistic pathogens in the environment.We thank Andrew Grant and Craig Winstanley for providing strains and reagents. Some C. elegans and bacterial strains were provided by the Caenorhabditis Genetics Centre, which is funded by NIH’s Office of Research Infrastructure Programs (P40 OD010440). This research was funded by a grant from the Biotechnology and Biological Sciences Research Council (grant number BB/I012222/1) to O.R. O.R. also acknowledges funding from the Royal Society (University Research Fellowship). EQM was supported by a scholarship from the Winston Churchill Foundation of the United States, and EGR by an EUfunded Erasmus bursary (Lifelong Learning Programme). We also thank two anonymous referees for their valuable comments.This is the final published version. It first appeared at http://onlinelibrary.wiley.com/doi/10.1002/ece3.1461/abstract

Dating app users after two years: A Dark Triad amplification

A 2-year longitudinal study examined how dating app use (N = 82, 36 women) affects changes in personality (i.e., the Dark Triad and Big Five traits), and visual social media use (i.e., dating apps, Instagram). Dating app users were higher in narcissism and Machiavellianism after two years but not in the Big Five traits. Early time and sessions on dating apps were associated with more sessions on dating apps, more time on Instagram, and higher narcissism later. Men increased in narcissism, women decreased in extraversion, openness, conscientiousness, and increased in agreeableness. The use of dating apps affects personality into an antagonistic direction, especially women