DOI: 10.5061/dryad.s1rn8pkhk
title: Population differences in melanin pigmentation plasticity in response to a seasonal cue

description: Adaptive plasticity allows organisms to interact with heterogeneous
 environments and respond to environmental change. Population-level
 comparisons of plasticity provide insights into the selective factors
 driving plasticity evolution and the properties of reaction norms that are
 likely to evolve. We test how thermal environments shape melanin
 pigmentation plasticity in response to a seasonal cue in the white-lined
 sphinx moth, Hyles lineata. We compare how melanization is affected by
 photoperiod in two populations that experience different thermal
 environments: Colorado and Arizona. In a common garden experiment, we
 quantified two aspects of melanin pigmentation, melanic area and darkness,
 and measured their reaction norms in response to photoperiod. If thermal
 environment drives differences in melanin plasticity in response to
 photoperiod, then the reaction norms should differ in intercept (higher
 melanization in Colorado larvae across the range of photoperiods, due to
 colder temperatures), slope (steeper in Arizona larvae, due to a larger
 range of temperatures across relevant photoperiods), and shape (linear in
 Arizona larvae and quadratic in Colorado larvae, due to the relationship
 between photoperiod and temperature). Results are partially consistent
 with these predictions: the Arizona population had a steeper slope, but a
 higher intercept. The Colorado population likely relies more heavily on
 temperature cues to inform melanization, requiring lower temperatures to
 increase melanin. Populations did not differ in reaction norm shape,
 suggesting that while slope and intercept are labile, there may be
 constraints on the evolution of shape. Because only two populations were
 compared in this study, replication at the level of population is needed
 to corroborate the generality of these results. This study highlights the
 complexity of plasticity evolution and the need to consider multiple cues
 and selective pressures, as well as potential constraints on the evolution
 of reaction norms.
description: # *Hyles* population comparison Comparison of melanin pigmentation
 plasticity in two populations of *Hyles lineata* larvae from Arizona and
 Colorado. Below is a description of the data and software files. 
 **Variable descriptions for "pop_data.csv":** * Larval ID =
 unique individual identifier * pop_origin = whether individual is
 descended from the AZ or CO wild-caught populations * photoperiod =
 daylength treatment * full_treatment = a concatenation of the population
 and photoperiod factors * 5th_day = date that 5th instar was reached *
 blocking_day = date that pupal stage was reached * development_time =
 duration of 5th star (blocking_day - 5th_day), left blank if pupal stage
 was not reached (see notes column for more details) * larval_mass = larval
 mass in grams, taken on same day as the photos * pupal_mass = pupal mass
 in grams, left blank if pupal stage was not reached (see notes column for
 more details) * sex = male or female if known, left blank if pupal stage
 was not reached because sexing not possible * Experiment_Notes = notes,
 especially on lost samples * percent_R, percent_G, percent_B = percent
 melanic area in the red, green, and blue spectra, note that only percent_G
 was used in final analyses * gray_R, gray_G, gray_B = grayscale values in
 the red, green, and blue spectra * darkness_G = darkness value calculated
 from gray_G * initials = initials of photo analyzer **Variable
 descriptions for "daylength__temp_data.csv":** * Population = CO
 or AZ * Date = Date without the year * Year = year from 2014-2023  * Max =
 maximum temperature on that date/ year in °F * max_temp = maximum
 temperature on that date/ year in °C, this was the variable used in
 analyses * Min = minimum temperature on that date/ year in °F * max_temp
 = minimum temperature on that date/ year in °C, this was the variable used
 in analyses * Average = mean temperature on that date/ year in °F *
 mean_temp = mean temperature on that date/ year in C, this was the
 variable used in analyses * daylight_hours = length of daylight hours on
 that date/year **Variable descriptions for
 "daylength__temp_data.csv":** * Population = CO or AZ * Date =
 Month * Year = Year 2014-2023  * Monthly_mean_min = Mean minimum temp for
 that month and year (°C) * Monthly_mean_max = Mean maximum temp for that
 month and year (°C) * Monthly_average_mean= Mean average temp for that
 month and year (°C) **Description of "Population_Photos.zip"
 file:** This zip archive includes all of the larval photographs used for
 image analysis. Images are in Canon cr2 raw image format. Images are named
 with the individual ID which matches individual ID in the data files.
 Names begin with either "AZ" or "CO" to designate the
 population origin.