DOI: 10.5061/dryad.9w0vt4bb6
title: From individuals to populations: How intraspecific competition shapes thermal reaction norms

description: 1. Most ectotherms follow the temperature-size rule (TSR): in cold
 environments individuals grow slowly but reach a large asymptotic length.
 Intraspecific competition can induce plastic changes of growth rate and
 asymptotic length and competition may itself be modulated by temperature.
 2. Our aim is to disentangle the joint effects of temperature and
 intraspecific competition on growth rate and asymptotic length. 3. We used
 two distinct clonal lineages of the Collembola Folsomia candida, to
 describe thermal reaction norms of growth rate, asymptotic length and
 reproduction over 6 temperatures between 6°C and 29°C. In parallel, we
 measured the long-term size-structure and dynamics of populations reared
 under the same temperatures to measure growth rates and asymptotic lengths
 in populations and to quantify the joint effects of competition and
 temperature on these traits. 4. We show that intraspecific competition
 modulates the temperature-size rule. In dense populations there is a
 direct negative effect of temperature on asymptotic length, but there is
 no temperature dependence of the growth rate, the dominant factor
 regulating growth being competition. The two lineages responded
 differently to the joint effects of temperature and competition on growth
 and asymptotic size and these genetic differences have marked effects on
 population structure along our temperature gradient. 5. Our results
 reinforce the idea that the TSR response of ectotherms can be modulated by
 biotic and abiotic stressors when studied in non-optimal laboratory
 experiments. Untangling complex interactions between environment and
 demography will help to understand how size will respond to environmental
 change and how climate change may influence population size structure.
description: These datasets come from two experiments made in the laboratory.
 In the first one we have raised isolated collembola from two lineages
 (labelled TO and HA) from the species Folsomia candida from birth to death
 and have recorded their growth and reproduction. This has been done at six
 different temperatures. We have used the growth trajectories of each
 individual to measure its growth rate and its asymptotic body
 length. In the second set of experiment we have raised
 populations of the same lineages from the same species at the same six
 temperatures. We have counted and measured the size of each individual
 every week or so to describe the dynamics of the population size structure
 over time. From these dynamics we have measured the
 growth rate and asymptotic size of some cohorts and the average adult and
 juvenile densities at the time of these measurements.
description: RData.zip <br> In the RData.zip file
 we have gathered all the information to describe the population size
 structure of the different populations.<br> The 06_HA_r1.RData file
 contains the information for the population structure size dynamics of the
 first replicate (r1) of the clone HA raised at 6°C (06).<br> The
 26_TO_r3.RData is for the population number 3 of TO raised at
 26°C.<br> <br> "SizeClass" "time"
 "counts" "Date" 0.0125 0 0
 2010-08-12     #zero individual between 0 and 0.0125mm long counted that
 day (2010-08-12).<br> 0.0375 0 0 2010-08-12<br> 0.0625 0 0
 2010-08-12<br> 0.0875 0 0 2010-08-12<br> 0.1125 0 0
 2010-08-12<br> 0.1375 0 0 2010-08-12<br> 0.1625 0 0.4
 2010-08-12<br> 0.1875 0 0.6 2010-08-12<br> 0.2125 0 0.6
 2010-08-12 #0.6 individual between 0.1875 and 0.2125mm long counted that
 day.<br> 0.2375 0 1 2010-08-12 <br>
 "counts" is the average number of collembola of size
 "SizeClass" (in mm) counted at the date "Date" which
 corresponds to a certain number of days ("time") after the
 beginning of the followup of that population.<br> Note that the
 number of individuals counted for each size class is not a whole number
 because it has been averaged over about 3 to 5 different photos of the
 same population taken the same day
 (see https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0064387 for details). <br> These files have been used to generate the different panels of the figure S2 in the article.   We also provide a spreadsheet with different sheets. Cumulative fecundity of isolated individuals This table gathers the data used to plot the Figure 2 A and B. It give the total number of eggs produced par individuals when they were raised individually.<br> 1.    Individual code : unique identification code for the individuals<br> 2.    Total number of eggs laid during the whole lifespan by each individual<br> 3.    Clone : either HA or TO<br> 4.    Temperature (°C) at which each individual has been raised. Clutch_size Individual code: : unique identification code for the individuals<br> Clutch number     : P1 is for the first clutch, P2 for the second clutch laid by an individual, etc.<br> Number of eggs : number of eggs in each clutch<br> Clone : either HA or TO<br> Temperature (°C): the t° at which each individual has been raised.<br> This dataset was used to plot the Figure S4A. <br> Growth and asymptotic size of isolated individuals and of cohorts in populations This table gathers all the growth rate and asymptotic body length measurements made on the isolated individuals and on the cohorts in the populations.<br> We have 6 columns:<br>     1.    Clone : either HA or TO, the labels of the two clones of Folsomia candida<br>     2.    Temperature : the temperature at which the individuals or population have been maintained (°C)<br>     3.    Adult density : the mean number of adults per container when the measurement has been made,  it is set to 1 for the isolated individuals...<br>     4.    Measure : the numeric value of the measure (either growth in mm/day or asymptotic length in mm)<br>     5.    Adult_type : it tells if the the measurement has been made  on large adults or small ones. Small adults are present in the trimodal populations where two type of adults can coexist. It therefore only concern the asymptotic body length made on some of the cohorts in these populations.<br>     6.    Variable : type of variable measured : either growth rate or asymptotic body length. Cohort asymptotic sizes in the populations Measurements of asymptotic length in the populations.<br>     1.    Cohort :  unique identification code for the studied cohorts in the populations<br>     2.    Box : unique identification code for the box or population<br>     3.    Clone : Clone label HA or TO<br>     4.    Temperature : °C<br>     5.    Time : number of days since the beginning of the population followup.<br>     6.    Size : asymptotic length (mm) of the cohort measured in a population.<br>     7.    Adult_type : adult type of the measured cohort - small or large - in the trimodal populations where two types of adults coexist<br>     8.    Mean_Adult_Density : mean number of large adults per container when the size measurement is made.<br>     9.    Mean_Juvenile_Density : mean number of juveniles per container when the size measurement is made<br> This dataset is used to plot the Figure 2C, Figure 4B, S4B. Cohort growth rates in the populations <br> Box : : unique identification code for the box or population<br> Clone:  : Clone label HA or TO<br> Temperature (°C)<br> Time : : number of days since the beginning of the population followup.<br> MeanAduL : Mean length of the adults already present in the population (mm) when the measurement of growth rate of the cohort is made.<br> MeanJuvL: Mean length of the juveniles already present in the population (mm) when the measurement of growth rate of the cohort is made<br> Density: total number of individuals present in the population when the measurement of growth rate of the cohort is made.<br> DensAdu: Mean number of adults in the population when the measurement of growth rate of the cohort is made.<br> DensJuv: Mean number of juveniles in the population when the measurement of growth rate of the cohort is made.<br> Biosurface: Mean total biosurface of Collembola in the population when the measurement of growth rate of the cohort is made.(mm^2)<br> BiosurfAdu: Mean biosurface of adult Collembola in the population when the measurement of growth rate of the cohort is made. (mm^2)<br> BiosurfJuv: Mean biosurface of juveniles in the population when the measurement of growth rate of the cohort is made. (mm^2)<br> t0 and t1: time in days since the beginning of the population followup that define the beginning and end of the growth period of the cohort on which the growth rate has been measured.<br> Growth rate: growth rate of the cohort measured on the population structure diagram in mm/day.<br> Cohort number: within each population we have measured one or several cohorts)<br> This dataset is used to plot the Figure S5.