DOI: 10.5061/dryad.s1rn8pkf0
title: The effects of sex on extinction dynamics of Chlamydomonas reinhardtii depend on the rate of environmental change

description: The continued existence of sex, despite many the costs it entails, still
 lacks an adequate explanation, as previous studies demonstrated that the
 effects of sex are environment-dependent: sex enhances the rate of
 adaptation in changing environments, but the benefits level off in benign
 conditions. To the best of our knowledge, the potential impact of
 different patterns of environmental change on the magnitude of these
 benefits received less attention in theoretical studies. In this paper, we
 begin to explore this issue by examining the effect of the rate of
 environmental deterioration (negatively correlated with population
 survival rate), on the benefits of sex. To investigate the interplay of
 sex and the rate of environmental deterioration, we carried out a
 long-term selection experiment with a unicellular alga (Chlamydomonas
 reinhardtii), by manipulating mode of reproduction (asexual, facultative
 or obligate sexual) and the rate of environmental deterioration (an
 increase of salt concentration). We monitored both the population size and
 extinction dynamics. The results revealed that the relative advantage of
 sex increased at the intermediate rate and plateaued at the highest rate
 of environmental deterioration. Obligate sexual populations had the
 slowest extinction rate under the intermediate rate of environmental
 deterioration, while facultative sexuality was favoured under the high
 rate-treatment. To the best of our knowledge, our study is the first to
 demonstrate that the interplay of sex and the rate of environmental
 deterioration affects the probability of survival, which indicates that
 mode of reproduction may be an important determinant of survival of the
 anthropogenic-induced environmental change.
description: # The effects of sex on extinction dynamics of Chlamydomonas reinhardtii
 depend on the rate of environmental change
 [https://doi.org/10.5061/dryad.s1rn8pkf0](https://doi.org/10.5061/dryad.s1rn8pkf0) The provided files contain the data regarding the population size dynamics of experimental populations prior to extinctions ('o.d.\_readings'); slope of the regression lines representing mean decline of population size as a function of time ('slope\_of\_the\_regression\_lines'); extinction dynamics with respect to time ('time\_extinction'); extinction dynamics with respect to salt concentration ('salt\_extinction'); ## Description of the data and file structure All files are in .csv form. The columns include the treatment groups (mode of reproduction and the rate of environmental change) and the response variable. The levels within 'mode of reproduction' (categorical independent variable) are: 'Asexual', 'F.sexual' (Facultative sexual) and 'O.sexual' (Obligate sexual). The levels within 'the rate of environmental change' (categorical independent variable) are: 'Gradual', 'Moderate' and 'High'. The binary response variable for the survival analyses (the files 'time\_extinction' and 'salt\_extinction', respectively) is death/survival per each time point (either 'cycle' or 'salt', depending on the file): 0 for death event, 1 for survival. The continuous response variables for the population size analyses are: 'od', the optical density (OD750), corresponding to the level of absorbance of the 750 nm-wavelength waves ('o.d.\_readings'); 'slope of the regression line' ('slope\_of\_the\_regression\_lines'). ## Code/Software All the analyses were carried out using RStudio 2021.09.0 (R Core Team, 2017). The packages ‘plyr’ and ‘survival’ were used for the analysis of population size dynamics and extinction dynamics, respectively; the packages : ‘gplots’, ‘ggplot2’, ‘plothrix’, ‘RColorBrewer’ were used for visualisation of population size dynamics, while ‘survminer’ was used for visualisation of extinction dynamics.