DOI: 10.5061/dryad.2v6wwpzvp
title: Data from: Temperature has an overriding role compared to photoperiod in regulating the seasonal timing of winter moth egg hatching

description: To accurately predict species’ phenology under climate change, we need to
 gain a detailed mechanistic understanding of how different environmental
 cues interact to produce the seasonal timing response. In the winter moth
 (Operophtera brumata), seasonal timing of egg hatching is strongly
 affected by ambient temperature and has been under strong climate
 change-induced selection over the past 25 years. However, it is unclear
 whether photoperiod received at the egg stage also influences timing of
 egg hatching. Here, we investigated the relative contribution of
 photoperiod and temperature in regulating winter moth egg development
 using two split-brood experiments. We experimentally shifted the
 photoperiod eggs received by 2-4 weeks compared to the actual calendar
 date and measured the timing of egg hatching, both at a constant
 temperature and in combination with two naturally changing temperature
 treatments – mimicking a cold and a warm year. We found an eight-fold
 larger effect of temperature compared to photoperiod on egg development
 time. Moreover, the very small photoperiod effects we found were
 outweighed by both between- and within-clutch variation in egg development
 time. Thus, we conclude that photoperiod received at the egg stage does
 likely not play a substantial role in regulating the seasonal timing of
 egg hatching in the winter moth. These insights into the regulatory
 mechanism of seasonal timing could have important implications for
 predicting insect climate change adaptation, as we might expect different
 targets of selection depending on the relative contribution of different
 environmental cues.
description: We investigated whether photoperiod received at the egg stage
 influences the seasonal timing of egg hatching in the winter moth, both as
 a cue on its own and in interaction with temperature. In two split-brood
 experiments, we determined egg hatching date after giving eggs either an
 early or late season photoperiod treatment, with naturally changing day
 lengths shifted 2-4 weeks earlier or later compared to the actual calendar
 date. Temperature was kept constant in the first experiment, while the
 second experiment also incorporated two naturally changing temperature
 treatments – mimicking a cold and a warm year – to investigate the
 relative contribution of temperature and photoperiod.
 Eggs were collected from wild females (31 clutches and 20
 clutches, for experiment 1 and 2 respectively), with each clutch of eggs
 split into sub-clutches and divided over the different photoperiod and
 photoperiod-temperature treatments. Raw egg hatching data (i.e. 2-3
 observations per week of the number of freshly hatched caterpillars per
 sub-clutch) have been processed by calculating the median hatching date
 per sub-clutch (D50, i.e. the day at which 50% of the sub-clutch has
 hatched). D50 data were used for the statistical analyses and have been
 deposited here, together with the raw temperature logger data from the
 experiment.
description: # Temperature has an overriding role compared to photoperiod in regulating
 the seasonal timing of winter moth egg hatching
 ## Description of the data
 and file structure Raw data belonging to the manuscript "Temperature
 has an overriding role compared to photoperiod in regulating the seasonal
 timing of winter moth egg hatching". We investigated whether
 photoperiod received at the egg stage influences the seasonal timing of
 egg hatching in the winter moth, both as a cue on its own and in
 interaction with temperature. In two split-brood experiments, we
 determined egg hatching date after giving eggs either an early or late
 season photoperiod treatment, with naturally changing day lengths shifted
 2-4 weeks earlier or later compared to the actual calendar date.
 Temperature was kept constant in the first experiment, while the second
 experiment also incorporated two naturally changing temperature treatments
 – mimicking a cold and a warm year – to investigate the relative
 contribution of temperature and photoperiod. **NB: Treatment names consist
 of photoperiod treatment: (1) control [0 weeks shift], (2) very early
 season photoperiod [-4 weeks], (3) early season photoperiod [-2 weeks/K],
 (4) late season photoperiod [+2 weeks/L], and (5) very late season
 photoperiod [+4 weeks]; and temperature treatment: mimicking cold year
 1999 [K] and warm year [W]** \--- Split-brood experiment 1: Photoperiod
 experiment 2013-2014 files \ Contains all
 experimental data collected from the photoperiod experiment (EggPhot2014),
 incl. for each sub-clutch (ClutchID) their origin (TubeID=female parent -
 31 females in total - incl. catch info for this female parent i.e. Area,
 Site, Tree and NovemberDate=Catch date as julian dates with origin
 2013-10-31); the treatment the ClutchID was assigned to (Treatment); the
 number of eggs in the sub-clutch (Eggs, at least 12); and when the
 sub-clutch hatched (D50Calc, i.e. julian dates with origin 2014-03-31).
 **NB: Median hatching date (D50Calc) per sub-clutch was only calculated if
 at least 10 eggs in the sub-clutch hatched.**
 \ Specifies the photoperiod treatment
 assignment for each ventilated box that eggs were kept in during the
 experiment. Needed to interpret the temperature data from the temperature
 loggers (see below). In total, 3 boxes per treatment (3x5 treatments = 15
 boxes). \ Temperature logger
 data for boxes 1-5. \
 Temperature logger data for boxes 6-10.
 \ Temperature logger data
 for boxes 11-15. Logger data per logger (LoggerName) measuring the
 Temperature for each ventilated box(LocationName/Location) for each
 measuring timepoint (Year, Month, Day, Date, Hour, Minute, Time), as
 obtained from the internal winter moth Access database (SysUser=who
 entered the data in the database, SysDate=when data entry happened, TempID
 and LocationID=database specific IDs). \--- Split-brood experiment 2:
 Photoperiod-temperature experiment 2000-2001 files
 \ Contains all experimental data
 collected from the photoperiod experiment (EggPhotTemp2001,
 ExperimentName=RN2001), with the same variables as described for above for
 . Treatment [KK]=Cold year and -2 weeks
 photoperiod; Treatment [WL]=Warm year and +2 weeks photoperiod.
 \ Temperature logger data for
 used incubators (indicated by Treatment name), with the same variables as
 described for above for .
 \--- Experimental photoperiod and temperature treatments
 \ Photoperiod treatments as used in the
 Photoperiod experiment (1 tab per treatment), giving the sunrise and
 sunset times in hours (HH:MM) for the calendar day the treatment was
 shifted to (date) for every day of the experiment (actual date). Note that
 this experiment started on January 15, while the same [-2 weeks] and [+2
 weeks] treatments were used in the Photoperiod-temperature experiment, but
 starting earlier on December 12. \
 \ Temperature treatments mimicked a specific
 year (Cold: 1973, Warm: 1999). For each day, a three-phase temperature
 cycle was used: 6 hours at the daily minimum temperature (h1), 12 hours at
 the mean of the daily maximum and the daily average (h7), and 6 hours at
 the daily average for each year (h19). ## Code/Software All code needed to
 reproduce the manuscript's data analysis using R are included.See the
 file for used R version and package versions. \---
 Split-brood experiment 1 Script: &lt;1_EggPhotoExp2014_analysis.R&gt; R
 script to reproduce the analysis and visualization (incl. manuscript
 figures) of the 2014 winter moth egg photoperiod experiment: Does
 photoperiod received at the egg stage affect the seasonal timing of egg
 hatching? \--- Split-brood experiment 2 Script:
 &lt;2_scripts/2_EggPhotoTempExp2001_analysis.R&gt; R script to reproduce
 the analysis and visualization (incl. manuscript figures) of the 2001
 winter moth egg photoperiod-temperature experiment: What is the relative
 contribution of photoperiod and temperature on the timing of egg hatching?
 \--- Visualization of experimental photoperiod and temperature treatments
 Script: &lt;3_visualize-treatments.R&gt; R script to visualize the
 photoperiod and temperature treatments as used in the two experiments,
 showing how they change over the season to mimic naturally changing
 environmental conditions. See for used R version and
 package versions.