DOI: 10.5061/dryad.pk0p2ngxs
title: Data from: Asymmetrical evolution of cross inhibition in zooplankton: Insights from contrasting phosphorus limitation and salinization exposure sequences

description: Understanding the evolutionary responses of organisms to multiple
 stressors is crucial for predicting the ecological consequences of
 intensified anthropogenic activities. While previous studies have
 documented the effects of selection history on organisms' abilities
 to cope with new stressors, the impact of the sequence in which stressors
 occur on evolutionary outcomes remains less understood. In this study, we
 examined the evolutionary responses of a metazoan rotifer species to two
 prevalent freshwater stressors: nutrient limitation and increased
 salinization. We subjected rotifer populations with distinct selection
 histories (salt-adapted, low phosphorus-adapted, and ancestral clones) to
 a reciprocal common garden experiment and monitored their population
 growth rates. Our results revealed an asymmetric evolutionary response to
 phosphorus (P) limitation and increased salinity. Specifically, adaptation
 to low P conditions reduced rotifer tolerance to increased salinity,
 whereas adaptation to saline conditions enhanced tolerance to P
 limitation, and such evolved cross-tolerance was more pronounced under
 moderately saline conditions. Our findings, therefore, underscore the
 importance of considering historical stressor regimes to improve our
 understanding and predictions of organismal responses to multiple
 stressors, and also have significant implications for ecosystem
 management.
description: # Data from: Asymmetrical evolution of cross inhibition in zooplankton:
 Insights from contrasting phosphorus limitation and salinization exposure
 sequences
 [https://doi.org/10.5061/dryad.pk0p2ngxs](https://doi.org/10.5061/dryad.pk0p2ngxs) **Short description of experiment**: To test the impact of adaptation to P limitation or increased salinization on rotifer population growth rate when confronting the alternative stressor, we performed a factorial-designed common garden experiment. Specifically, we assigned rotifer populations with different selection histories (SelHist), i.e., LP adapted, salt adapted and ancestral populations, to the combination of 2 food quality treatments (FoodQual: High P and Low P food) and 2 salinity treatments (SAL: High Sline and Low Saline).  For each treatments, we applied 3 clone replictes (Clone) and 3 chemostat replicates (Chem_repl), resulting a total of 108 experimental units. During the experiment, the size of each population were monitored to calculate their population growth rates at daily basis. Meanwhile, we refreshed the food medium and restarted each population by randomly selected and transferred 10 individuals to fresh medium. The experimetn lasted for 9 days and we analyzed the data for last three days where population growth rates for all populations had stabilized. Features for the algal food, such as cell size and density in the chemostats, were measured by the coulter counter every day. Algal stoichiometric features (i.e., carbon, nitrogen and phosphorus) were also measured at the start of the experiment. This studies consists of three datafiles: (1) The dataset ‘Population growth rates.csv’ contains rotifer population counts during the common garden experiment (2) the dataset ‘Food algae_size_density.csv’ contains cell sizes and cell densities of chemostat cultures used as food source for the rotifers during the common garden experiment (3) the dataset ‘Algal_stoichiometry.csv’ contains data on the elemental content (carbon, nitrogen and phosphorus) of the algae in the chemostat cultures **Explanation of variables:** **Explanatory variables used in multiple data files** * Day: day in the experiment - Chem_repl: chemostat replicate (3 replicates) * FoodQual: food quality treatment in common garden experiment: LP: P-limited chemostats; HP: P sufficient chemostats) **Population_growth_rates.csv** Variable names: * SelHist: factor to which population had  adapted during prior selection experiment (LP: LP-food, Salt: saline; Ancest: naieve ancestral) - Clone: genotype * SAL: salinity treatment in common garden treatment (in LP treatments: 1.5 g/L NaCl; in HP treatments: 3 g/L NaCl) - initial: total number of female rotifers at start of time interval * final: total number of female rotifers at end of time interval - r: calculated exponential population growth rate (day-1) **Food_algae_size_density.csv** Cell diameters and densities of food algae as characterized with a Coultercounter Variable names: * diameter: average cell diameter (µm) - density: number of cells per mL **Algal_stoichiometry.csv** Variable names: * Nconc: nitrogen concentration (µmol/L) - Cconc: carbon concentration (µmol/L) * Pconc: phosphorus concentration (µmol/L) - CtoP: molar C:P ratio * CtoN: molar C:N ratio - NtoP:  molar N:P ratio #### Code/Software **Data_Analysis_Annotated.R**: This script analyzes how zooplankton evolve cross-tolerance to phosphorus limitation and salinization by modeling growth-rate responses across different environmental and selection histories. It fits mixed-effects models, compares treatment effects, and calculates tolerance differences using paired contrasts and Holm-corrected statistics.