Figure 2. A novel methodology shows color pattern diversity correlates with latitude.
A) 1. We took digital photographs of wasp faces, with antennae removed to allow a clear view of the color patterns. Photographs were standardized for potential differences in lighting using the MICA toolbox52 in ImageJ. 2. We placed landmarks on the images in homologous locations and then used patternize to align the images and mask out regions of noninterest for color patterns. 3. Pixels in each image were classified as black, red, or yellow, based on similarity to a color palette derived from the images using recolorize. 4. Binary rasters for each color in the zone map were subjected to a PCA transformation to represent color patterns in multi-dimensional space. The first two PCs of 23 statistically significant PCs are shown, as well as some representative faces to visualize how patterns are separated in PC space. A summary of the importance of each significant principal component is provided in Table S3.
B) The relationship between face diversity and latitude across the range of sampling sites fit with a linear regression line. Face diversity was measured as the mean Euclidean pairwise distance between all faces within a population from the PCA scores (shown in A4). Points representing sites in Louisiana are colored red, and those representing sites in New York are colored yellow. See also Figure S4.