The competition-tolerance trade-off as a cause of species turnover along environmental gradients: The role of population differentiation
Data files
Jan 27, 2026 version files 299.32 KB
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Germination_rate_of_Anatolian_pops_for_competition_experiment.csv
8.68 KB
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Length_of_longest_leaf_through_time_for_Anatolian_pops.csv
32.21 KB
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Pappus_seed_mass_of_Anatolian_populations.csv
43.94 KB
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Precipitation_and_temperature_in_the_10_Mediterranean_and_10_steppe_sites_in_Anatolia.csv
17.23 KB
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README.md
6.47 KB
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RIIs_for_Anatolian_populations.csv
24.94 KB
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Seedling_emergence_Anatolian_pops_for_257_days.csv
162.74 KB
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SLA_of_Anatolian_populations.csv
3.11 KB
Abstract
One of the latest advances in studying species distribution proposes that the universal occurrence of a trade-off between competition and environmental tolerance explains the segregated distribution of closely related species along environmental gradients. Given that this proposition applies to species that are closely related, here we moved one step down and explored the possibility that a trade-off between competition and tolerance also controls the distribution of populations within species that occupy different environments. We tested our hypothesis with populations of the annual herb Centaurea solstitialis that grow at low versus high elevation (hereafter, Mediterranean versus steppe populations, respectively) in Anatolia. We characterized climatic conditions in which these populations grow and conducted a common garden, where we measured traits predicted to affect environmental tolerance, and an intraspecific competition experiment, that included different densities, with Mediterranean and steppe populations. We found that Mediterranean populations experience climatic conditions that appear more favorable for early growth than those experienced by steppe populations. Specifically, conditions are warmer and wetter upon this species emergence in the Mediterranean than steppe region. In addition, Mediterranean populations exhibited trait attributes typically associated with benign environments, whereas steppe populations displayed attributes thought to cope with harsh environments. These attributes included smaller seeds, lower dormancy, faster emergence and seedling growth, and higher specific leaf area in Mediterranean than steppe populations. Finally, individuals from Mediterranean populations were stronger competitors than those from steppe populations. Together, these findings suggest that adaptation to harsh environments comes at the expense of competitive ability in our study populations, and that this compromise may control their separated distribution along elevational/climatic gradients. Population differentiation may thus precede the later observed turnover of related species along environmental gradients proposed to be caused by the competition-tolerance trade-off.
Dataset DOI: 10.5061/dryad.gf1vhhn3d
Description of the data and file structure
Data are from two experiments conducted under common conditions in the greenhouse.
Files and variables
File: Length_of_longest_leaf_through_time_for_Anatolian_pops.csv
Description: This file includes the length of the longest leaf at 30, 60, and 105 days after emergence in our common garden experiment.
Variables
- Sampling (days): Days after seedling emergence on which leaf length was recorded.
- Region: Region from where populations were collected; that is, Mediterranean or Steppe.
- Population: Number given to study populations.
- Individual: Number of the individual measured within each population.
- Length longest leaf (cm): Length of the longest leaf in cm. Empty cells respond to the fact that there was no individual to measure in pots.
- rgr (cm day-1): Relative growth rate in cm per day. That is, the length of the leaf divided by 30, 60, or 105. Empty cells respond to the fact that there was no individual to measure in pots.
File: Pappus_seed_mass_of_Anatolian_populations.csv
Description: This file includes the mass of seeds with a pappus used in our common garden experiment.
Variables
- Date: Weighing date.
- Region: Region from where populations were collected; that is, Mediterranean or Steppe.
- Pop#: Number given to study populations.
- Ind#: Number of the individual measured within each population.
- Pappus seed#: Number of the seed measured within each individual.
- Pappus seed mass (g): Seed mass in grams.
File: Precipitation_and_temperature_in_the_10_Mediterranean_and_10_steppe_sites_in_Anatolia.csv
Description: This file has precipitation and temperature data of weather stations located near Mediterranean and steppe populations in our study.
Variables
- Site: Name of the site where the weather station is located.
- Latitude (N): Latitude coordinate where sites are located.
- Longitude (E): Longitude coordinate where sites are located.
- Elevation (m): Meters above sea level at which sites are located.
- Month: Name of the month of the year.
- Mean precipitation (kg/m2): Average precipitation for the given month across years in kilograms per meter square.
- Mean temperature (ºC): Average temperature for a given month across years in Celsius degrees.
File: SLA_of_Anatolian_populations.csv
Description: File with data of specific leaf area (sla) of Anatolian populations in our common garden experiment.
Variables
- Region: Region from where populations were collected; that is, Mediterranean or Steppe.
- Population: Number given to study populations.
- Individual: Number of the individual measured within each population.
- Leaf weight (g): Dry weight in grams of the leaf used to calculate sla.
- Leaf area (cm2): Area in square centimeters of the leaf used to calculate sla.
- SLA: Specific leaf area (leaf area divided by leaf weight).
File: RIIs_for_Anatolian_populations.csv
Description: File with data of relative interaction indices (RIIs) of Anatolian populations in our competition experiment.
Variables
- Pot: Pot number
- Density: Number of plants per pot.
- Ind within pot: Number of the individual measured within the pot.
- Target: Origin of the individual measured within the pot.
- Competitor: Origin of the individual serving as a competitor within the pot.
- Pop: Name of the population included in the study.
- Ind within pop: Number of the individual within a given population.
- Dry weight (g): Dry weight of the aboveground biomass of seedlings in grams. This variable has empty cells for cases in which individuals were missing in the pot.
- RII: Relative interaction index. This column has empty cells for density 1 and for cases where the target or the competitor was missing in the pot.
File: Seedling_emergence_Anatolian_pops_for_257_days.csv
Description: This file contains the data for seedling emergence in our common garden experiment.
Variables
- Region: Region from where populations were collected; that is, Mediterranean or Steppe.
- Population: Number given to study populations.
- Individual: Number of the individual measured within each population.
- Seeds added to pots: Number of seeds added to pots.
- D1 to D257: Days at which emergence within pots was recorded. This variable has empty cells when no emergence was observed.
- prop: This variable is repeated from D4 (first day after seeding with emergence in pots) to D257 (last day at which emergence was observed). This variable is the proportion of seedlings that emerged at a give day (emerged seedling divided the number of seeds added to pots).
- cum: This variable is repeated from D4 (first day after seeding with emergence in pots) to D257 (last day at which emergence was observed). This variable is the cumulative proportional emergence for a given sampling day.
- Timson: Timson’s index. Column with empty cells for pots with no emergence.
File: Germination_rate_of_Anatolian_pops_for_competition_experiment.csv
Description: This file includes germination data of populations used in the competition experiment of our study. Specifically, they are linked to the following sentence in our manuscript: “Seeds were pre-germinated at room temperature on one Whatman paper (#3) placed inside plastic dishes (9 cm diameter) watered with 10 mL distilled water [n=3 dishes (one per individual) with 20 seeds per dish]. Seed germination was used to estimate germination rate for 15 days (Timson’s index).”
Variables
- Region: Region from where populations were collected; that is, Mediterranean or Steppe.
- Population: Number given to study populations.
- Dish: Replicate the number of the dish where seeds were germinated. Values go from 1 to 3.
- Seeds added to dishes: Number of seeds placed within each dish for germination.
- 1-15: Days at which germination was recorded.
- Prop1-15: Proportion of seeds germinated at each sampling day from day 1 to day 15. Sampling was conducted on days 1, 2, 3, 4, 5, 6, 7, 9, 11, 13, and 15.
- Cum1-10: Cumulative germination proportion for each sampling day.
- Timson: Timson’s index.