DOI: 10.5061/dryad.x95x69pv6
title: Data from: Responses of a widespread pest insect to extreme high temperatures are stage-dependent and divergent among seasonal cohorts

description: Insect populations in temperate climates can show seasonal differences in
 demographic rates. Extreme high-temperature events (EHTs) are increasing
 in frequency across all seasons. These may, in turn, disrupt insects’
 season-specific demographic strategies. However, whether insect
 populations respond to EHTs in a season-specific fashion is not known, but
 may be critical for forecasting their responses to climate change. We
 conducted a series of common garden experiments measuring the inherent
 vital rates of spring, summer, and autumn cohorts of a global nonmigratory
 pest, the oriental fruit moth (Grapholita molesta), under constant mild
 temperatures, EHT exposures at different life stages, and short-term
 heat-hardening followed by EHT exposure at different life stages. We
 simultaneously conducted a 4-year survey of G. molesta in orchards to link
 our experimental results to observed population dynamics in the field. We
 encountered intrinsic variation in vital rates and reproductive traits
 among seasonal cohorts, such that summer cohorts had higher intrinsic
 population growth rates but smaller eggs than spring and autumn cohorts.
 Moreover, these responses varied among life stages to which the EHT was
 applied. Pre-acclimation via heat-hardening did not strongly affect these
 results but did slightly increase growth rates when applied to late-stage
 larvae. These results were qualitatively recovered in natural population
 time-series, with moderate EHTs enhancing population growth in the spring
 and reducing it in autumn. Our results underscore the importance of
 climatic seasonality in shaping season-specific thermal responses to EHTs
 among ectotherms. Season-specific EHT responses can potentially enhance
 growth of weak spring cohorts and depress growth of autumn cohorts failing
 in dormancy, thereby contributing to insects’ annual population
 persistence. Our study helps clarify how a deeper understanding of season
 and life-stage-specific heat responses can enable a more informed
 forecasting and management of multivoltine insect populations under
 climate change. Here are the raw data of this research.
description: Lab experiment:  We conducted a common garden
 experiment to assess whether the three seasonal cohorts had different
 vital rates under benign climate conditions. For the grand-offsprings of
 each seasonal cohort, we added 40 newly laid eggs of <em>G.
 molesta</em> into the calyx cavity of a single apple. This was
 repeated for at least twenty apples per cohort. We then placed the
 inoculated apples under a mild climate (25±1°C, RH: 60±10%, and 16 Light:
 8 Dark). We randomly photographed and measured the length of over 47 newly
 laid eggs for each seasonal cohort. After hatching, the young larvae fed
 inside their apple until they became mature larvae
 (3<sup>rd</sup>-4<sup>th</sup> instar) and then
 left the apple. We counted the larvae emerging from fruits, then
 transferred each one to its own small plastic tube (0.6 cm in diameter and
 5 cm in length) for pupation. Once adults emerged, we randomly paired
 newly eclosing adults (male and female) into plastic cups (6 cm in
 diameter and 8 cm in length) fed with 5% honey-water solution in a cotton
 ball. Mated females could lay eggs on the wall of plastic cups. We renewed
 all cups every day and counted the number of eggs on the cup until the
 adults died. At least 20 pairs of adults were tested per seasonal
 cohort. To investigate the basal demographic responses
 to EHTs for seasonal cohorts of <em>G. molesta</em>, we
 conducted additional common garden experiments where EHTs were applied to
 a particular life stage (eggs, young larvae, mature larvae emerging from
 fruits and young adults). We did not choose the pupal stage to be tested
 in this experiment because a previous study (Zheng et al., 2017) in this
 species suggested pupae to be resistant to EHTs. For each seasonal cohort,
 we prepared 20 Fuji apples (replicates) in the test groups of EHT exposure
 on eggs, young larvae, or mature larvae, and prepared 10 Fuji apples
 (replicates) in the test group of EHT exposure on new-emerging adults. For
 all the treatments, we added 40 newly laid eggs of <em>G.
 molesta</em> in the calyx cavity of each apple, and then placed all
 inoculated apples under mild rearing conditions (25±1°C, RH: 60±10%, and
 16 Light: 8 Dark) in climate-controlled chambers. For each test group,
 when individuals developed into the first day of their focal life stage,
 we moved them into a new climate-controlled chamber with a heat-stress
 condition of 38±1°C, RH 60±10%, and light for 7 hours. We chose this
 heat-stress condition as an EHT exposure based on results from Zheng et
 al. (2017) and Liang et al. (2014), and natural high temperatures and
 durations in China’s temperate apple-growing regions in recent years which
 match the ‘typical’ EHTs. After this EHT exposure, we returned the
 individuals to the mild rearing condition and continued to rear them until
 they died. For the testing group of heating on eggs, young larvae (L1), or
 mature larvae (L3), we tracked the survival, age stage and sex of each
 tested individual across their entire life cycle. All resulting
 demographic rates were calculated as described above in the benign
 conditions.  To investigate the effects of
 heat-hardening on demographic responses, we ran a third set of experiments
 exactly as previously described, but this time with a brief heat-hardening
 phase preceding the EHT which consisted of a two-hour pre-treatment at
 35±1°C, RH: 60±10%, recovery at 25±1°C for 30 minutes, followed by a
 7-hour EHT exposure as previously described. We chose this heat-hardening
 condition based on Zheng et al. (2017) and our pilot experiments.
 Demographic data was collected during every life cycle stage and
 transition during the experiment as described above.
 Field survey: We conducted field surveys for
 population density of <em>G. molesta</em> during their growing
 season (March to September) from 2019 to 2021 at Xingcheng, China
 (40.62°N, 120.74°E) and from 2018 to 2021 at Yingkou, China (40.20°N,
 122.13°E). At each site, we selected between 1 apple orchard in Yingkou
 and 3 apple orchards in Xingcheng separated by at least 1 kilometer. Five
 <em>G. molesta </em>traps were installed in each orchard,
 which were spaced at least 200 meters apart. Traps consisted of a 30 cm
 diameter plastic basin filled 2/3 with water and a pheromone lure fixed
 above the center of the water. We counted the number of captured adults
 per device every day from Mar 1<sup>st</sup> to Sep
 30<sup>th </sup>in each year. We renewed water and removed all
 trapped adults every morning, and the lure was replaced once a month. We
 obtained hourly records of temperatures and precipitation of 2018-2021 in
 each site from the database of CPC Global Unified Temperature and CPC
 Global Unified Gauge-Based Analysis of Daily Precipitation (https://psl.noaa.gov/data/gridded/index.html) and calculated the corresponding daily average temperatures, daily maximum temperatures, and daily accumulated precipitation.
description: # Responses of a widespread pest insect to extreme high temperatures are
 stage-dependent and divergent among seasonal cohorts
 [https://doi.org/10.5061/dryad.x95x69pv6](https://doi.org/10.5061/dryad.x95x69pv6) ## Description of the data and file structure **Explanation for sheet names of the raw data (raw data.xlsx):** **Lab experiments:** "Adult trait under No EHT": Adult traits for the individuals of 3 cohorts experiencing no extreme high temperature events. "Development time under No EHT": Development time for the immature individuals of 3 cohorts experiencing no extreme high temperature events. "N in lifestage under No EHT": Numbers of moths in each life stage of 3 cohorts experiencing no extreme high temperature events. "Egg_length under No EHT": Length of eggs of 3 cohorts experiencing no extreme high temperature events. "Adult trait under EHT": Adult traits for the individuals of 3 cohorts experiencing high temperature events appied to different life stages. "Immature duration uder EHT": Development time for the immature individuals of 3 cohorts experiencing high temperature events appied to different life stages. "N in lifestage under EHT": Numbers of moths in each life stage of 3 cohorts experiencing high temperature events appied to different life stages. "Adult trait under harden+EHT": Adult traits for the individuals of 3 cohorts experiencing heat hardening and high temperature events appied to different life stages. "Immature duration uder harden+EHT": Development time for the immature individuals of 3 cohorts experiencing heat hardening and high temperature events appied to different life stages. "N in lifestage under harden+EHT": Numbers of moths in each life stage of 3 cohorts experiencing heat hardening and high temperature events appied to different life stages. **Field survey:** "Population dynamics of OFM": Population dynamics of oriental fruit moth in 2 sites. "Meteorological data": Time series of climatic data corresponding to the population dynamics in 2 sites. ### Files and variables #### File: raw\_data.xlsx **Description:**  ##### Variable: No EHT experiment: Seasonal cohorts of a species (Spring, Summer and Autumn cohorts) EHT experiment: Seasonal cohorts of a species (Spring, Summer and Autumn cohorts) and Life stages (egg, young larval, mature larval, adult) with a EHT treatment.  Harden+EHT experiment: Seasonal cohorts of a species (Spring, Summer and Autumn cohorts) and Life stages (egg, young larval, mature larval, adult) with a heat hardening and EHT treatment. In No EHT experiment, EHT experiment, and Harden+EHT experiment, the units of numeric variables:     fecundity: individuals; longevity_female: days; longevity_male: days; Duration of egg and larval in fruit: days; Duration of larval out of fruit: days; Pupa duration: days; Immature duration: days; egg_number: individuals; Larval_out_of_fruit_number: individuals; Pupa_number: individuals; Eclosion_number: individuals; egg_length: cm. Field survey on population dynamics: latitude, longitude, date, year, apple_orchards_id, Daily temperature, precipitation In Field survey on population dynamics, the units of numeric variables:     abundance: individuals. In Meteorological data, the units of numeric variables:     Daily maximum temperature: °C; Daily minimum temperature: °C; Daily mean temperature: °C; precipitation: mm. ## Code/software We used packages of base (v4.2.2; R Core Team, 2022),  car (v3.1-1; John and Sanford, 2019), MASS (v7.3-58.2; Venables & Ripley, 2002), stats (v4.2.2; R Core Team, 2022), mvgam (v1.10; Clark & Wells, 2023), multcomp (v1.4-22; Hothorn et al., 2008) in R (v4.2.2; R Core Team, 2022) to analyze our datasets.