Distance transform: a tool for the study of animal colour patterns
Article first published online: 7 JUN 2013
© 2013 The Authors. Methods in Ecology and Evolution © 2013 British Ecological Society
This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
Methods in Ecology and Evolution
Volume 4, Issue 8, pages 771–781, August 2013
How to Cite
Taylor, C. H., Gilbert, F., Reader, T. (2013), Distance transform: a tool for the study of animal colour patterns. Methods in Ecology and Evolution, 4: 771–781. doi: 10.1111/2041-210X.12063
- Issue published online: 9 AUG 2013
- Article first published online: 7 JUN 2013
- Accepted manuscript online: 25 APR 2013 07:46AM EST
- Manuscript Accepted: 17 APR 2013
- Manuscript Received: 3 JAN 2013
- image analysis;
- individual recognition;
- MATLAB ;
- The information in animal colour patterns plays a key role in many ecological interactions; quantification would help us to study them, but this is problematic. Comparing patterns using human judgement is subjective and inconsistent. Traditional shape analysis is unsuitable as patterns do not usually contain conserved landmarks. Alternative statistical approaches also have weaknesses, particularly as they are generally based on summary measures that discard most or all of the spatial information in a pattern.
- We present a method for quantifying the similarity of a pair of patterns based on the distance transform of a binary image. The method compares the whole pattern, pixel by pixel, while being robust to small spatial variations among images.
- We demonstrate the utility of the distance transform method using three ecological examples. We generate a measure of mimetic accuracy between hoverflies (Diptera: Syrphidae) and wasps (Hymenoptera) based on abdominal pattern and show that this correlates strongly with the perception of a model predator (humans). We calculate similarity values within a group of mimetic butterflies and compare this with proposed pairings of Müllerian comimics. Finally, we characterise variation in clypeal badges of a paper wasp (Polistes dominula) and compare this with previous measures of variation.
- While our results generally support the findings of existing studies that have used simpler ad hoc methods for measuring differences between patterns, our method is able to detect more subtle variation and hence reveal previously overlooked trends.