DOI: 10.5061/dryad.gf1vhhmtk
title: The role of growing degree-days in explaining moth species distributions at broad scales

description: Growing degree-days (GDD), an estimate of an organism’s growing season
 length, has been shown to be an important predictor of Lepidopteran
 species’ distributions and could be influencing Lepidopteran range shifts
 to climate change. Yet, one understudied simplification in this literature
 is that the same thermal threshold is used in the calculations of GDD for
 all species instead of a species-specific threshold. By characterizing the
 phenological process influenced by climate, a species-specific estimate of
 GDD should improve the accuracy of species distribution models (SDMs). To
 test this hypothesis, we use published lab-estimated thermal thresholds
 and modeled the current geographic distribution of 30 moth species native
 to North America. We found that the predictive performance of models based
 on a species-specific estimate of GDD was indistinguishable from models
 based on a standard estimate of GDD. This is likely because GDD was not an
 important predictor of these species’ distributions. Our findings suggest
 that lab-estimated thermal thresholds may not always scale up to be
 predictive at broad scales and that more work is needed to leverage the
 data from lab experiments into SDMs to accurately predict species’ range
 shifts in response to climate change.
description: # The role of growing degree-days in explaining moth species distributions
 at broad scales Data used to generate the species' BDT and assess how
 the quality of the experiments may have influenced the accuracy of BDT.
 **Description of the Data and file structure** quality_test.csv: data used
 to assess the quality of the experiment that generated the base
 development temperature for the 30 species used in the analysis Column
 names, Definition, Units BDT: Base development temperature estimate from
 the experiment; in degrees Celsius ltm: lowest temperature treatment
 included in the experiment, stages included; in degrees Celsius adj_ltm:
 adjusted lowest temperature treatment included in the experiment if more
 than one ltm was provided; took the mean if the ltm was different for
 different life stages; in degrees Celsius ltd: lowest temperature with
 data on developmental rate (i.e., mortality or no development detected at
 temperature treatments lower than this, if different from lowest
 temperature measured), stages included; in degrees Celsius adj_ltd:
 adjusted lowest temperature with data on developmental rate; took the mean
 if the ltd was different for different life stages; in degrees Celcius
 ntm: number of temperature treatments, stages and other notes included
 adj_ntm: adjusted number of temperature treatments if more than one ntm
 was provided; only including constant temperature treatments; took the
 mean if the ntm was different for different life stages ls: number of life
 stages that developmental rate was measured lab_experiment: indication of
 whether the experiment took place in the lab; 1 = lab experiment; 0 = not
 a lab experiment field_experiment: indication of whether the experiment
 took place in the field; 1 = field experiment; 0 = not a field experiment
 notes: additional notes author - link: Reference information for the study
 Sharing/access Information Data was derived from: Jarok, V., Honk, A.,
 Magarey, R. D., & Skuhrovec, J. (2011). Developmental database for
 phenology models: Related insect and mite species have similar thermal
 requirements. Journal of Economic Entomology, 104(6), 18701876.
 [https://doi.org/10.1603/EC11247](https://doi.org/10.1603/EC11247)