DOI: 10.5061/dryad.8w9ghx3zs
title: Data from: Color variation and visual modeling provide no support for adaptive coloration in a blue crayfish

description: The adaptationist dogma among research on animal colors has recently come
 into question, as several studies have suggested that bright, conspicuous
 colors in animals are not always adaptive, but evolutionarily neutral.
 However, demonstrating that a color trait is evolutionarily neutral is
 complicated—there is no consensus as to what qualifies as sufficient
 evidence for a color trait to be considered neutral. Our study discusses
 these issues while investigating the function of coloration in a
 conspicuously colored blue crayfish, Cambarus monongalensis, which
 inhabits semi-terrestrial burrows and rarely interacts with the surface.
 By correlating sex and size with color variables, we found that three body
 regions of C. monongalensis do not vary in color with respect to sex or
 size, thereby rejecting two of our adaptive hypotheses. Additionally,
 visual models of crayfish and predators suggest that crayfish may not be
 able to distinguish body colors across the body and against backgrounds,
 but that predators can distinguish these colors. By integrating these
 results with prior studies, we discuss how bright colors in crayfish may
 be an ideal system to investigate the neutral theory of color evolution.
 Ultimately, such research may challenge the adaptationist dogma in
 research on animal color and other phenotypes.
description: # Color variation and visual modeling provide no support for adaptive
 coloration in a blue crayfish Dataset DOI:
 [10.5061/dryad.8w9ghx3zs](10.5061/dryad.8w9ghx3zs) ## Description of the
 data and file structure This dataset was collected as part of a study
 investigating color variation in the Blue Crawfish, *Cambarus
 monongalensis*, and how these colors may be perceived by both conspecifics
 and potential predators. In March and April 2024, 88 adult crayfish were
 collected from a population in Claysville, Pennsylvania, using daytime
 burrow excavation and nighttime hand collection during surface activity
 following rainfall. Each individual was sexed and measured for carapace
 length as an indicator of body size. Juveniles (carapace length &lt;15 mm)
 were excluded to avoid ontogenetic variation. Reflectance spectra were
 measured using an Ocean Optics Jaz UV/VIS spectrometer from three body
 regions: the dorsal carapace, the dorsal claw (manus), and the pollex.
 Four key colorimetric variables (mean brightness, chroma in blue and red
 regions, and hue) were extracted for each region. Additionally,
 reflectance spectra were recorded for common background substrates (e.g.,
 brown leaves, green leaves, sand, burrow, and non-burrow soil) from the
 same habitat. ### Files and variables **File Description** The file
 **back_spec.csv** contains spectral reflectance measurements for various
 background objects associated with Cambarus monongalensis habitats. Each
 column represents a different measurement, with the wl column indicating
 the specific wavelength of light in nanometers. Variables: * wl:
 Wavelength of light (in nanometers) - Brownleaf: Measurements for brown
 leaves (5 replicates: 1.1 to 1.5) * Greenleaf: Measurements for green
 leaves (5 replicates: 1.1 to 1.5) - Sand: Measurements for sand (5
 replicates: 1.1 to 1.5) * Burrowmud: Measurements for mud from burrows (5
 replicates: 1.1 to 1.5) - Nonburrowmud: Measurements for mud not from
 burrows (5 replicates: 1.1 to 1.5) **File Description** The file
 **final_merged_monongalensis_data.xls** contains morphological,
 demographic, collection, and colorimetric data for individual Cambarus
 monongalensis crayfish. Each row corresponds to a single individual
 crayfish, and each column represents a different trait or measurement.
 Blank cells in this dataset indicate missing or unavailable data. Unlike
 placeholders (e.g., "NA" or "null"), true blank values
 prevent analysis errors by ensuring compatibility with statistical
 software. Data Structure Crayfish_ID: Unique identifier or name for each
 crayfish individual. Species: All entries are Cambarus monongalensis.
 Collection_date: Date the crayfish was collected (YYYY-MM-DD). Location:
 Collection location for the specimen. Sex: Sex of the individual (Male or
 Female). Demographic: Demographic category (Female, Male Form I, or Male
 Form II). Carapace_length: Carapace length in millimeters (body size
 measurement). Spec_data_collection_date: Date the spectral reflectance
 data were collected. Individual: Filename under which the individual’s
 spectral data was saved. **Colorimetric Variables:** These variables
 summarize reflectance properties of different body regions across the
 light spectrum (typically 300–700 nm), using metrics from the pavo R
 package. Each is named using the format:
 Metric_BodyRegion_LowerWavelength_UpperWavelength B1: Mean brightness B2:
 Brightness contrast H1: Mean hue H2: Hue contrast S1: Mean chroma
 (saturation) S2: Chroma contrast Examples: B1_carapace_300_700: Mean
 brightness of the carapace from 300–700 nm. S2_claw_400_700: Chroma
 contrast in the claw from 400–700 nm. H1_tip_300_700: Mean hue of the tip
 region from 300–700 nm. For detailed definitions of colorimetric metrics,
 see:
 [https://pavo.colrverse.com/reference/summary.rspec.html](https://pavo.colrverse.com/reference/summary.rspec.html) The file **Illumination.csv** contains spectral irradiance data representing different natural light environments, as reported in Johnsen (2006): "Ecological importance of color in aquatic organisms: biology and evolution of light environments" (Annual Review of Ecology, Evolution, and Systematics). Each column represents a distinct illumination condition, and the wl column indicates the wavelength of light in nanometers. Blank cells in this dataset indicate missing or unavailable data. Unlike placeholders (e.g., "NA" or "null"), true blank values prevent analysis errors by ensuring compatibility with statistical software. Data Structure wl: Wavelength of light (in nanometers) Starlight (sunspot max): Spectral irradiance measured in forested starlight (max) Starlight (sunspot min): Spectral irradiance measured in forested starlight (min) Full Moon: Spectral irradiance of forested full moon All irradiance values are in arbitrary units, normalized or scaled for comparative purposes, and measured across the visible and near-UV spectrum (approx. 300–700 nm). Reference Johnsen, S. (2006). Ecological importance of color in aquatic organisms: biology and evolution of light environments. Annual Review of Ecology, Evolution, and Systematics, 37, 57–88. [https://pubmed.ncbi.nlm.nih.gov/16481568/](https://pubmed.ncbi.nlm.nih.gov/16481568/) **R Scripts:** #### **`Color_analysis_monongalensis.r`** **Purpose**: Analyze color variation data using reflectance measurements. **Input File**: * `final_merged_monongalensis_data.csv` (contains merged reflectance/color data). * Generates statistical summaries, visualizations (e.g., plots), or processed datasets --- #### **`Visual_modeling_monongalensis.r`** **Purpose**: Models photoreceptor responses for varying environmental conditions (illumination, backgrounds). **Input Files**: * `final_merged_monongalensis_data.csv` (reflectance data). * `illumination.csv` (illumination condition spectra data). * `back_spec.csv` (background reflectance spectra). * **Various `.csv` files** containing modeled photoreceptor sensitivities for different combinations of: * **Visual systems** * **Illumination conditions** (e.g., forest shade, daylight) * **Background types** (e.g., green leaf, sand) * **File Naming Convention**: * Outputs are labeled systematically from the bootstrapping color distance modeling as `[VisualSystem]. [Illumination]. [Background].csv`* (e.g., *`databootds.garter.starmax.sand.csv`). **dS.mean** and **dL.mean:** Average short-term and long-term color distances, respectively. * **dS.lwr / dS.upr** and **dL.lwr / dL.upr:** Corresponding lower and upper bounds of 95% confidence intervals, indicating the precision of estimates. * All .csvs for different visual systems, illumination, and backgrounds for the visual modeling are in the vis.*model.csv.*files.zip file