DOI: 10.5061/dryad.8gtht7706
title: Breakpoint phenological responses in high-Arctic arthropods

description: Many arthropod species show earlier seasonal activity trends with warming,
 but these responses cannot continue indefinitely. Beyond a threshold,
 phenological responses may no longer keep pace with climate change. While
 many studies estimate linear phenological responses to climate, few test
 for breakpoint responses. Here, across a 28-year time series, we examined
 linear and breakpoint responses to temperature and snowmelt across 15
 arthropod taxa in seven plots from high-Arctic Greenland, a region
 experiencing pronounced warming. Our meta-analysis revealed support for a
 breakpoint response in two of six phenological driver and event
 combinations. This breakpoint response was found in the onset and peak of
 activity to the timing of snowmelt, where activity advanced with snowmelt
 until a threshold, after which the relationship levelled off. While we
 also found a breakpoint response in peak phenology to temperature, this
 disappeared when controlling for snowmelt in the model, underscoring the
 importance of considering multiple environmental cues to prevent incorrect
 inferences about plasticity limits. Most responses did not show evidence
 of a breakpoint in phenological response, and instead showed consistent
 phenological sensitivity to environmental cues across our study period.
 Our findings point to a need for a wider assessment of the prevalence of
 breakpoint phenological responses to climate change.
description: # Keeping up with climate change - have Arctic arthropods reached their
 phenological limits? ## Description of the data and file structure This
 repository contains the code and data necessary to replicate data
 analyses, figures, and tables in: ***Keeping up with climate change - have
 Arctic arthropods reached their phenological limits?*** ## Data usage
 guidelines ### *Note on data provenance and licensing:* This dataset
 includes original data and materials created by the authors, which are
 released under the Creative Commons Zero (CC0 1.0) Public Domain
 Dedication. These original contributions are free to use without
 restriction. ##### File: df\_phenology\_metrics ###### Description:
 Estimated phenological metrics (onset, peak, and end of annual activity)
 for all arthropod taxa sampled across years and plots at Zackenberg,
 Northeast Greenland. ###### *Variables* * **Year**: Year of sampling. *
 **Plot**: Vegetation type in which arthropods were sampled. *
 **SpeciesID**: Arthropod taxon sampled (taxonomic resolution: family,
 super-family, or order). * **TotalAbundance**: Total number of individuals
 of the arthropod taxon caught in a given plot and year. * **Onset**:
 Estimated start day of the year of activity. * **Peak**: Estimated peak
 day of the year of activity. * **End**: Estimated end day of the year of
 activity. * **Duration**: Estimated duration of activity, calculated as
 the number of days between onset and end. #### **Files with climate
 data:** **File:** Snowmelt_Climatestation*_*updated.csv
 **Description:** Annual estimates of snowmelt timing. ###### *Variables* *
 **Year**: Year of sampling. * **SnowmeltDOY**: Day of year of annual
 snowmelt. **File:** Air_temp*_*30_days*_*rolling.csv
 **Description:** Temperature data calculated as the 30-day average
 temperature preceding a mean phenological event. ###### *Variables* *
 **Year**: Year of sampling. * **Plot**: Vegetation type in which
 arthropods were sampled. * **SpeciesID**: Arthropod taxon sampled
 (taxonomic resolution: family, super-family, or order). *
 **TotalAbundance**: Total number of individuals of the arthropod taxon
 caught in a given plot and year. * **Onset**: Estimated start day of the
 year of activity. * **Peak**: Estimated peak day of the year of activity.
 * **End**: Estimated end day of the year of activity. * **Duration**:
 Estimated duration of activity, calculated as the number of days between
 onset and end. * **Onset_DOY**: Mean onset of activity across years. *
 **Peak_DOY**: Mean peak of activity across years. * **End_DOY**: Mean end
 of activity across years. * **Onset_temp**: Average air temperature (°C)
 over the 30 days preceding the mean phenological event (Onset_DOY) for
 each taxon-plot-year combination. * **Peak_temp**: Average air temperature
 (°C) over the 30 days preceding the mean phenological event (Peak_DOY) for
 each taxon-plot-year combination. * **End_temp**: Average air temperature
 (°C) over the 30 days preceding the mean phenological event (End_DOY) for
 each taxon-plot-year combination. #### **Files with output from the
 breakpoint analysis used for meta-analysis:**
 **File:** df_summary_onset_snow_final_new.csv
 **File:** df_summary_peak_snow_final_new.csv
 **File:** df_summary_end_snow_final_new.csv
 **File:** df_summary_onset_temp_final_new.csv
 **File:** df_summary_peak_temp_final_new.csv
 **File:** df_summary_end_temp_final_new.csv
 **File:** df_summary_onset_snow_temp_final_new.csv
 **File:** df_summary_peak_snow_temp_final_new.csv
 **File:** df_summary_end_snow_temp_final_new.csv
 **File:** df_summary_onset_temp_snow_final_new.csv
 **File:** df_summary_peak_temp_snow_final_new.csv
 **File:** df_summary_end_temp_snow_final_new.csv
 **Description:** Statistical output from the breakpoint analysis is
 calculated separately for each phenological event. There are three
 summaries for snowmelt as a single predictor, three summaries for
 temperature as a single predictor, three summaries for snowmelt
 controlling for temperature, and three summaries for temperature
 controlling for snowmelt. ###### *Variables* * **Plot**: Vegetation type
 in which arthropods were sampled. * **SpeciesID**: Arthropod taxon sampled
 (taxonomic resolution: family, super-family, or order). * **Intercept**:
 Intercept of the first segment before the breakpoint. * **Slope1**: Slope
 of the regression line before the breakpoint. * **Slopediff**: Difference
 in slope before and after the breakpoint (Slope2 - Slope1). * **Pvalue**:
 P-value associated with the test for a change in slope at the breakpoint.
 * **Break**: Estimated year or position of the breakpoint (i.e., where the
 slope changes). * **Meanslope**: Mean slope across the full time series
 (no breakpoint model). * **Meanslopediff**: Difference between the mean
 slope and Slope1. * **SEslope**: Standard error of the slope before the
 breakpoint. * **SEslopediff**: Standard error of the slope difference. *
 **CI_lwr**: Lower bound of the confidence interval for the slope
 difference. * **CI_upr**: Upper bound of the confidence interval for the
 slope difference. * **n**: Number of years (observations) used in the
 model. * **AIC_0**: Akaike Information Criterion (AIC) for the
 no-breakpoint model (single slope). * **AIC_1**: AIC for the segmented
 (breakpoint) model. * **OriginalSlope**: Slope from the original
 unsegmented model (prior to breakpoint analysis). * **OriginalSE**:
 Standard error of the original slope. * **Order**: Ecological role or
 trophic guild of the arthropod taxon (e.g., "Decomposer"). *
 **Habitat**: Dominant habitat or vegetation type where the taxon was
 found. ### Code/software Software used: R Statistical Software (v4.4.1; R
 Core Team 2024) Packages: “tidyverse” v. 2.0.0, “mgcv” v. 1.9-1,
 "metafor" v. 4.8-0 ### Access information #### Other publicly
 accessible locations of the data: This dataset was originally informed by
 environmental and phenological observations published by the Greenland
 Ecosystem Monitoring Programme under the Creative Commons
 Attribution-ShareAlike 4.0 International (CC-BY-SA-4.0) license. However,
 no raw data or materials under that license are included in this Dryad
 submission. Only derived summaries or references to those external sources
 remain, and all third-party content has been clearly cited below for
 attribution and reproducibility. ##### Appropriate ways to cite
 third-party sources: **Phenological observations:** Observations at
 Zackenberg were provided by the Greenland Ecosystem Monitoring Programme.
 Family data for arthropods are available at:
 [https://data.g-e-m.dk/](https://data.g-e-m.dk/). **Cite as:** Greenland
 Ecosystem Monitoring (2025). BioBasis Zackenberg - Arthropods - Arthropod
 emergence (Version 1.0). [Data set] [CC-BY-SA-4.0]. Greenland Ecosystem
 Monitoring.
 [https://doi.org/10.17897/V285-Z265](https://doi.org/10.17897/V285-Z265)
 **Environmental predictors:** Temperature and snowmelt observations for
 Zackenberg were also provided by the Greenland Ecosystem Monitoring
 Programme. Data are available at:
 [https://data.g-e-m.dk/](https://data.g-e-m.dk/). A formatted version,
 including all estimated temperature and snowmelt timing values, is
 included in this repository. If using the original data downloaded
 directly from the database, please cite as: * Greenland Ecosystem
 Monitoring (2025). *ClimateBasis Zackenberg – Air temperature – Air
 temperature, 200 cm @ 60 min sample (°C)* (Version 1.0). [Data set]
 [CC-BY-SA-4.0]. Greenland Ecosystem Monitoring.
 [https://doi.org/10.17897/XV96-HC57](https://doi.org/10.17897/XV96-HC57) *
 Greenland Ecosystem Monitoring (2025). *ClimateBasis Zackenberg –
 Precipitation – Snow depth – 180 min sample (m)* (Version 1.0). [Data set]
 [CC-BY-SA-4.0]. Greenland Ecosystem Monitoring.
 [https://doi.org/10.17897/7RVV-Z412](https://doi.org/10.17897/7RVV-Z412)