Population differences in melanin pigmentation plasticity in response to a seasonal cue
Data files
Jul 01, 2025 version files 7.91 GB
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daylength_temp_data.csv
273.41 KB
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monthly_means.csv
6.27 KB
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pop_data.csv
42.90 KB
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Population_Photos.zip
7.91 GB
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README.md
2.74 KB
Abstract
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.
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.