10.5061/DRYAD.VB549
Badiane, Arnaud
Macquarie University
University of Valencia
Pérez i de Lanuza, Guillem
University of Porto
García-Custodio, María del Carmen
University of Valencia
Carazo, Pau
University of Valencia
Font, Enrique
University of Valencia
Data from: Colour patch size and measurement error using reflectance
spectrometry
Dryad
dataset
2018
Podarcis muralis
2018-04-25T00:00:00Z
2018-04-25T00:00:00Z
en
https://doi.org/10.1111/2041-210x.12801
33398745 bytes
1
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
1. Over the past twenty years, portable and relatively affordable
spectrophotometers have greatly advanced the study of animal coloration.
However, the small size of many colour patches poses methodological
challenges that have not, to date, been assessed in the literature. Here,
we tackle this issue for a reflectance spectrophotometry set-up widely
used in ecology and evolution (the beam method). 2. We reviewed the
literature on animal coloration reporting the use of reflectance
spectrophotometry to explore how the minimum measurable size of a colour
patch is determined. We then used coloured plastic sheets to create
artificial colour patches, and quantify the relationship between colour
patch size and distortions induced by resulting chimeric spectra (spectra
contaminated by an adjacent colour patch). Finally, we assessed the
generality of our findings using natural colour spots in the lizard
Podarcis muralis, as a biologically realistic model. 3. We found a lack of
consensus in the literature, frequently resulting in the rejection of
valid data or the potential inclusion of unreliable data. As expected, we
show that decreasing colour patch size reduces the reliability of
reflectance measurements, but also that spectral distortions resulting
from chimeric spectra depend on patch/background colour combinations. We
found similar results using natural colour spots in P. muralis. 4. We
propose a series of steps to avoid the pitfalls described above. First, we
provide guidelines on how to identify chimeric spectra and estimate the
minimum size of a measurable colour patch in order to avoid them. Second,
we show that reducing the probe-to-surface distance allows for more
accurate measurements and therefore improves the spectrophotometric
assessment of small colour patches. Third, we suggest that, as a general
rule of thumb, very small (< 2 mm) colour patches should be avoided
when using traditional spectrophotometry methods.
Spectra_3mmSpectra obtained at a 3-mm distance of the different
centre/surround colour combinations of the artificial coloured plastic
plates used in Experiment 1.Data_3mm.xlsxSpectra_5mmSpectra obtained at a
5-mm distance of the different colour combinations of the artificial
coloured plastic sheets used in experiment
1.Data_5mm.xlsxPmuralis_spectra_OVSSpectra of the UV outer-ventral scale
(OVS) displayed by Podarcis muralis, spectra of their orange ventral
coloration, and spectra of their black coloration. We also took chimeric
spectra including UV-OVS with the orange ventral coloration and with the
black colorationPmuralis_spectra.xlsx