The effects of sex on extinction dynamics of Chlamydomonas reinhardtii depend on the rate of environmental change
Data files
Sep 25, 2023 version files 89.65 KB
-
o.d._readings.csv
61.15 KB
-
README.md
2.07 KB
-
salt_extinction.csv
5.13 KB
-
slope_of_the_regression_lines.csv
7.12 KB
-
time_extintion.csv
14.19 KB
Abstract
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.
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.