DOI: 10.5061/dryad.4f4qrfjnb
title: Data from: A comparison of image statistics of peacock jumping spider colour patterns and natural scenes

description: The form of arbitrary sexual signals may be driven by the need to be
 detectable against the background or, alternatively, by selection for
 efficient processing by the nervous system. This latter alternative is a
 prediction of the sensory drive hypothesis extended to include efficient
 coding as a driver of the form of sexual signals. This hypothesis posits
 that animal visual systems are adapted to process the visual statistics of
 natural scenes, and that easily-processed stimuli induce a sensation of
 pleasure in the viewer. In support of this, natural scene statistics have
 been found to be preferred not only by humans, but by the peacock spider
 Maratus spicatus. Here we test if male peacock spiders of the highly
 sexually dimorphic Maratus genus generally (a) evolve colour patterns with
 image statistics that contrast with the natural background or (b) exploit
 a potential processing bias by evolving colour patterns with visual
 statistics similar to those of natural scenes. We analyse and compare
 multispectral images of male and female spiders of 21 Maratus species and
 of natural scenes similar to the spiders’ habitat. We find that the image
 statistics of male patterns diverge from those of natural scenes, whereas
 the statistics of female patterns do not. Our results support the idea
 that colour patterns evolve contrasting image statistics to increase
 conspicuousness and matching image statistics to be camouflaged. Any
 processing bias for natural scene image statistics in Maratus thus appears
 to play little role in the evolution of their sexual signals.
description: <strong>Multispectral imaging</strong>
 Multispectral imaging was done using a multispectral camera
 containing three bird-based optical filters (U, M, and L) previously
 described in Tedore and Nilsson (2019) and two additional filters
 previously described in Glenszczyk et al. (2021). By taking a weighted sum
 of these pre-existing camera filters, we calculated computational filters
 to generate new spectral sensitivities matching the spectral sensitivity
 of the salticid green receptor, which typically peaks around 530 nm (De
 Voe 1975; Yamashita and Tateda 1976; Blest et al. 1981; Zurek et al. 2015;
 Glenszczyk et al. 2021). The computational filter technique is further
 described in Tedore and Nilsson (2021) and Glenszczyk et al.
 (2021).
description: # A comparison of image statistics of peacock jumping spider colour
 patterns and natural scenes * Author: Marie-Christin Hardenbicker * Other
 contributors: Joseph Schubert, Cynthia Tedore * Date created: 2025-02-19
 #### Data and File Overview **Table of Contents** **File format: .txt** *
 spectralSlopesMaratus.txt * spectralSlopesNaturalScenes.txt * In
 Maratus.zip: * Data for Further Analysis contains 403 .txt files * In
 Natural Scenes.zip: * Data for Further Analysis contains 123 .txt files
 **File format: .mat (Matlab structure/table)** * imageSets.mat *
 salticidVirtualFilters_530nm_5realFilters.mat *
 salticidVirtualFilters_530nm_6realFilters.mat **File format: .m (Matlab
 script)** In Functions.zip: * circularWindow.m * prepMatFileNoMask.m *
 remGam.m * rotateAndCenter.m * round2even.m * squareCrop.m *
 developImgsAndFourierTransform.m **File format: .png** In Maratus.zip: *
 Images for Viewing on Digital Display contains 145 .png files * Images
 Edited for Fourier Transform contains 145 .png files * Fourier Plots 145
 .png files In Natural Scenes.zip: * Images for Viewing on Digital Display
 contains 41 .png files * Images Edited for Fourier Transform contains 41
 .png files * Fourier Plots 41 .png files **File format: .Rmd (R
 notebook)** * statisticalAnalysis.Rmd **Relationships between
 files/folders/code:** **File sets provided before running code** *
 imageSets.mat * salticidVirtualFilters_530nm_5realFilters.mat *
 salticidVirtualFilters_530nm_6realFilters.mat * Functions.zip **Code** *
 developImgsAndFourierTransform.m * statisticalAnalysis.Rmd **Files/Folders
 created by developImgsAndFourierTransform.m** * spectralSlopesMaratus.txt
 * spectralSlopesNaturalScenes.txt * Maratus * Natural Scenes * Recommended
 software/tools: Matlab R2024a; R version 4.4.1 **File/Folder/Code
 Details** **Details for: spectralSlopesMaratus.txt** * Description:
 Includes the calculated spectral slopes for Maratus. * Format(s): .txt,
 decimal separator = '.' * Size(s): 10 KB * Dimensions: 145 rows
 x 10 columns * Variables: * channel: spectral sensitivity of the channel
 that has been analysed (in nm) * species: species of Maratus * id: ID of
 the animal * sex: is the animal male, female or juvenile * extension_tube:
 size of the extension tube used in mm * slope: spectral slope calculated
 from multispectral image * hf: highest spatial frequency that was analysed
 * lf: lowest spatial frequency analysed * N: size of the squared image
 (one dimension) in pixels * Rsqrds: goodness of fit R^2 of the linear
 model **Details for: spectralNaturalScenes.txt** * Description: Includes
 the calculated spectral slopes for the multispectral images of random
 noise image stimuli. * Format(s): .txt, decimal separator = '.'
 * Size(s): 4 KB * Dimensions: 41 rows x 6 columns * Variables: * channel:
 spectral sensitivity of the channel that has been analysed (in nm) * id:
 ID of the multispectral photo * region: region the photo was taken at *
 location: region the photo was taken at * habitat: what kind of habitat
 the photo was taken at * slope: spectral slope calculated from
 multispectral image * Rsqrds: goodness of fit R^2 of the linear model
 **Details for: Data for Further Analysis (this folder can be found in
 Maratus.zip and Natural Scenes.zip)** * Description: This folder contains
 data of rotationally averaged amplitudes (of all, binned and cut
 frequencies, i.e., from low frequency cut off to high frequency cut off)
 that can be used for further analysis for example using a different
 software. It contains two subfolders: * File naming scheme:
 data_'range of frequencies'*'animal ID/photo
 ID'*'channel'.txt * File format(s): .txt, decimal separator
 = '.' * Folder size(s): * in Maratus.zip: 698 MB * in Natural
 Scenes.zip: 470 MB * File dimensions: varying number of rows depending on
 frequency range x 2 columns * Variables: * freqs: spatial frequency *
 meanAmpl: rotationally averaged amplitude **Details for: imageSets.mat** *
 Description: Matlab structure including multispectral imaging data and
 metadata for male and female Maratus abdomens and natural scenes *
 Format(s): .mat * Size(s): 2,13 GB * Dimensions: 112 rows x 15 columns *
 Variables: * id: image set ID * selection_data: not relevant * rgb_images:
 not relevant * project: which object was photographed M. spicatus
 ('Maratus') or 'Random Image Stimuli' *
 illumination_type: how were objects illuminated when photographed * taxon:
 species of the object * x_date_photographed: date and time photos were
 taken * gray_standard: logical array defining the gray standard in the
 image * transformation_variables: values that the image needs to be
 rotated and centered by (for images of M. spicatus) * square_mask: logical
 values needed to cut the biggest square out of M. spicatus abdomen *
 aperture: aperture of the camera * extension_tube_length: extension tube
 length used with the camera * lamp_tilt: vertical tilt of the lamp if used
 * animal_id: ID of M. spicatus * maturity: maturity of M. spicatus * sex:
 sex of M. spicatus * target_amplitude_spectrum: computer generated
 spectral slope of random image stimuli (before printing) * images: * id:
 image ID * exposure: exposure of the camera * filter: filter used (for
 more information on filters see Tedore and Nilsson (2019) and Glenszczyk
 et al. (2021). * quantum_catch_matrix: quantum catch image obtained by the
 camera * filter_position: filter position in the camera **Details for:
 salticidVirtualFilters_530nm_5realFilters.mat** * Description: Matfile
 containing coefficients to create computational Salticid green channel
 (530 nm) with 5 existing filters in multispectral camera. * Format(s):
 .mat * Size(s): 221 Byte **Details for:
 salticidVirtualFilters_530nm_6realFilters.mat** * Description: Matfile
 containing coefficients to create computational Salticid green channel
 (530 nm) with 6 existing filters in multispectral camera. * Format(s):
 .mat * Size(s): 228 Byte **Details for: Functions.zip** If you are running
 Matlab codes make sure to add the path of this folder to your code or have
 the functions in the same folder as your code and data. * Description:
 Folder containing custom written functions needed to run Matlab scripts.
 Includes: * circularWindow.m * prepMatFileNoMask.m * remGam.m: removes
 Gamma * rotateAndCenter.m * round2even.m * squareCrop.m * File format(s):
 .m * Folder size(s): 6 KB **Details for:
 developImgsAndFourierTransform.m** * Description: Matlab code that
 develops multispectral images and creates virtual filters from existing
 real filters in the multispectral camera. These virtual filter images are
 then analyzed for their spectral slope with a Fourier transform. This code
 can be used either to analyse multispectral images of Maratus (set
 imageType to ‚Maratus‘) or to analyze multispectral images of natural
 scenes (set imageType to ‚Natural Scenes‘). * Format(s): .m * Size(s): 19
 KB * Instructions: To use this code you have to first download all
 functions that are stored in the functions folder and the image data set
 called imageSets.mat as well as the coefficient files
 salticidVirtualFilters_530nm_5realFilters.mat and
 salticidVirtualFilters_530nm_6realFilters.mat. All files have to be in the
 same folder to run the code. Choose if you want to analyse multispectral
 images of Maratus or of natural scenes by specifying imageType. This code
 produces one folder named Maratus or Natural Scenes depending on what is
 specified under image Type. The Folder contains for folders: Images for
 Viewing on Digital Display, Images Edited for Fourier Transform, Fourier
 Plots, Data for Further Analysis. The code also produces a text file:
 either spectralSlopesMaratus.txt or spectralSlopesImageStimuli.txt
 depending on which image type is specified. **Details for: Images for
 Viewing on Digital Display (this folder can be found in Maratus.zip and
 Natural Scenes.zip)** * Description:This folder contains multispectral
 images with the typical sRGB gamma scaling removed such that brightness
 scales linearly with intensity when viewed on an sRGB-calibrated screen
 (not to be used for further analysis). * File format(s): .png * Folder
 size(s): * in Maratus.zip: 193.3 MB * in Natural Scenes.zip: 32.8 MB *
 File naming scheme: * in Maratus.zip: 'species_sex'*'animal
 ID'*'channel'.png * in Natural Scenes.zip:
 'photo_ID'_'channel'.png **Details for: Images Edited
 for Fourier Transform (this folder can be found in Maratus.zip and Natural
 Scenes.zip)** * Description:This folder contains multispectral images
 prepped for the Fourier transform (Maratus: cropped to squares, rotated
 and centered and windowed; Natural Scenes: cropped to squares and
 windowed). * File format(s): .png * Folder size(s): * in Maratus.zip: 7.7
 MB * in Natural Scenes.zip: 16.3 MB * File naming scheme: * in
 Maratus.zip: 'species_sex'*'animal
 ID'*'channel'.png * in Natural Scenes.zip:
 'photo_ID'_'channel'.png **Details for: Fourier Plots
 (this folder can be found in Maratus.zip and Natural Scenes.zip)** *
 Description:This folder contains plots of the results of the Fourier
 analysis of each of the multispectral images (prepped image, amplitude
 spectrum and rotationally averaged amplitude plotted against frequency). *
 File format(s): .png * Folder size(s): * in Maratus.zip: 51.2 MB * in
 Natural Scenes.zip: 58.3 MB * File naming scheme: * in Maratus.zip:
 'species_sex'*'animal ID'*'channel'.png * in
 Natural Scenes.zip: 'photo_ID'_'channel'.png **Details
 for: statisticalAnalysis.Rmd** * Description: R Notebook that reads in
 spectralSlopesMaratus.txt and spectralSlopesNaturalScenes.txt file and
 models the data as described in the statistical methods part of the
 manuscript. * Format(s): .Rmd * Size(s): 8 KB * Instructions: To use this
 code download the files spectralSlopesMaratus.txt and
 spectralSlopesNaturalScenes.txt and save in the same folder. Run the code.