Data and code for study entitled "Do environmental fluctuations during development affect trait variation? An experimental test with salinity"

We tested how developmental environments (freshwater, stable-saline, fluctuating-saline) influence variation in life-history traits (age at maturity, size at maturity, relative gut length, immunity) and reproductive traits in both sexes – females (egg number, egg size) and males (relative gonopodium length, sperm count, sperm velocity) at both young and old adult stages (before and after 12 weeks of mating).

We have attached the raw data spreadsheet (Raw data.xlsx). For young males, life-history and reproductive traits were measured in different individuals and are provided in separate sheets. For young females, old females, and old males, all traits were measured on the same individuals and are combined in a single sheet for each group. We analysed mean egg size in our models; individual egg size data for young females are also included in the raw data file.

The R code (Trait variability.R) was run using R v1.3.1093. Analyses used data from female.csv and male.csv.

----- Analytical approach -----

We used Bayesian multivariate mixed-effects models to estimate trait covariances and test whether developmental environment affected both trait means and variances, run separately for each age–sex group. Separate models were used for young males' life-history and reproductive traits. Environment (3 levels) was included as a fixed effect, with brood identity as a random effect. Traits including age at maturity, immunity, egg number (young females), and sperm count were power transformed to improve normality. Each model used four MCMC chains (5000 iterations, 1000 burn-in), with convergence confirmed (Rhat = 1) and effective sample sizes >1480.

To test environmental effects on trait variance, we modelled both trait means and standard deviations (SDs) on a log scale. We calculated:

lnVR = ln(SD1/SD2), to assess changes in raw variance

lnCVR = ln(CV1/CV2), to assess changes in relative variance (accounting for trait means)

We compared specific environment pairs to assess:

Effect of salinity: stable salinity vs freshwater

Effect of fluctuations: fluctuating salinity vs stable salinity