DOI: 10.5061/dryad.zs7h44j8z
title: Limited plasticity in thermally tolerant ectotherm populations: evidence for a trade-off

description: Many species face extinction risks owing to climate change, and there is
 an urgent need to identify which species' populations will be most
 vulnerable. Plasticity in heat tolerance, which includes acclimation or
 hardening, occurs when prior exposure to a warmer temperature changes an
 organism's upper thermal limit. The capacity for thermal acclimation
 could provide protection against warming, but prior work has found few
 generalizable patterns to explain variation in this trait. Here, we report
 the results of, to our knowledge, the first meta-analysis to examine
 within-species variation in thermal plasticity, using results from 20
 studies (19 species) that quantified thermal acclimation capacities across
 78 populations. We used meta-regression to evaluate two leading
 hypotheses. The climate variability hypothesis predicts that populations
 from more thermally variable habitats will have greater plasticity, while
 the trade-off hypothesis predicts that populations with the lowest heat
 tolerance will have the greatest plasticity. Our analysis indicates strong
 support for the trade-off hypothesis because populations with greater
 thermal tolerance had reduced plasticity. These results advance our
 understanding of variation in populations' susceptibility to climate
 change and imply that populations with the highest thermal tolerance may
 have limited phenotypic plasticity to adjust to ongoing climate warming.
description: Studies which measure thermal tolerance plasticity typically
 collect organisms from nature and acclimate them to different temperatures
 for defined periods of time in the lab before measuring thermal tolerance.
 Important methodological considerations for these types of studies include
 (1) for how long and at what temperature organisms are acclimated, (2) how
 fast the temperature is changed, and (3) whether measurements are made on
 field collected or F1 individuals, given that parental conditions are
 known to influence thermal plasticity. To identify publications for use in
 our study, we followed PRISMA (Preferred Reporting Items for Systematic
 reviews and Meta-Analyses) guidelines (supplemental figure S1). We
 searched titles, abstracts, and key words in Web of Science (Clarivate
 Analytics, Philadelphia, USA) using the following search string: (Thermal
 OR temperatures) AND (Lethal OR “Thermal tolerance” OR “Thermal limit” OR
 CTmax OR CTmin OR LT50 OR “freezing tolerance”) AND ("Local*
 Adapt*" OR "“Latitud* Var” OR Intraspecific). We conducted an
 initial literature search on 24 August 2019 and updated the search on 28
 July 2020. We also added studies that we were aware of but were not
 returned in the literature search. We used the following criteria for
 inclusion, where each study must have: (1) reported new results of
 whole-organism upper thermal limit in degrees Celsius for at least 2
 populations of the same species, (2) experimentally measured thermal
 tolerance after acclimating all individuals to at least two temperatures,
 (3) reported a measure of error for the thermal tolerance estimate, and
 (4) not measured tolerance of introduced species, hybrid lines, cultivars,
 domesticated species, or later generations of experimental laboratory
 populations (greater than F2). Although we initially included both cold
 and heat tolerance studies, we later excluded cold tolerance studies from
 our analysis due to insufficient data. Studies of cold tolerance, and
 additional studies that met criteria (1) and (2) but were excluded based
 on (3) and/or (4) are listed in supplemental table S1. We screened 400
 publications that measured thermal tolerances across populations and
 identified 20 studies to include in our meta-analysis, representing 19
 species. The studies that were accepted after looking through titles and
 abstracts but were later excluded from our analysis are listed in Table
 S1. We extracted data from each publication using relevant figures,
 tables, text, or supplementary material. In the case of figures, we used
 WebPlotDigitizer to extract means and error estimates.
description: GENERAL INFORMATION 1. Title of Dataset:
 acc_data_commoncontrol.csv and acc_data_reformatted_sorted.xlsx
 2. Author Information<br>     A. Principal Investigator
 Contact Information<br>         Name: Jordanna Barley<br>   
      Institution: University of Massachusetts Amherst<br>       
  Address: 160 Holdsworth Way, Amherst, MA 01003<br>         Email:
 jbarley@umass.edu 3. Date of data collection:
 2019-08-24 and 2020-07-28 4. Geographic location of
 data collection: CT, USA <br> DATA & FILE
 OVERVIEW 1. File List:<br>
 acc_data_commoncontrol.csv: dataset used in the main weighted
 meta-analytic models<br> acc_data_reformatted_sorted.xslx: dataset
 used earlier in the analysis process before the common control approach
 was decided on <br> DATA-SPECIFIC INFORMATION
 FOR: acc_data_commoncontrol.csv and
 acc_data_reformatted_sorted.xlsx 1. Number of
 variables: 33 2. Variable List:<br> study: study
 data was extracted from<br> taxon: latin name of species<br>
 phylum: phylum species bolongs to<br> common_name: common name of
 species<br> number_of_populations: number of populations for each
 species<br> ecosystem: ecosystem species inhabits (ocean,
 intertidal, terrestrial, freshwater)  <br> dispersal_mode: mode of
 dispersal for larval phase<br> acclimation_time: time researchers
 acclimated individuals in GENERATION TIME (ie. less than one generation,
 one generation, etc)<br> source_population: population that
 individual was obtained from, as defined by the researcher<br>
 latitude: latitude of the source population<br> longitude: longitude
 of the source population<br> life_history_stage: life history stage
 of the individual used in experimentation<br> sex: sex of the
 individual used in experimentation<br> acclimation_temperature_1:
 lower temperature in pairwaise contrast between acclimation temperature
 used<br> acclimation_temperature_2: upper temperature in pairwaise
 contrast between acclimation temperature used<br> measurement_level:
 level of the thermal tolerance measurement (ie. CTmax is an individual
 level measurement, LT50 is a population level measurement)<br>
 thermal_limit_type: type of thermal limit measuremed (CTmax, CTmin,
 LD50_high, LD50_lower)<br> thermal_limit_1: thermal limit for
 acclimation temperature #1<br> thermal_limit_2: thermal limit for
 acclimation temperature #2<br> thermal_limit_error_type: type of
 error association with the mean thermal limit (standard error, standard
 deviation, confidence intervals)<br> thermal_limit_error_1: error
 measurement for thermal_limit_1, given by the researchers<br>
 thermal_limit_error_2: error measurement for thermal_limit_2, given by the
 researchers<br> n_1: sample size for a given population 1<br>
 n_2: sample size for a given population 2<br> ni: total sample sized
 used for each population<br> max_temp: maximum temp. measured at the
 source population lat/long<br> min_temp: minimum temp. measured at
 the source population lat/long<br> mean_temp: mean temp. measured at
 the source population lat/long<br> temp_range: difference between
 max_temp and min_temp<br> upper_lower: factor distinguishing between
 upper and lower thermal limits<br> ARR: acclimation response ratio
 for a given comparison between two acclimation temperatures; (thermal
 limit 2- thermal limit 1)/(temp 2-temp 1)