Weller, H. I. | bioRxiv Science

bioRxiv2022

recolorize: improved color segmentation of digital images (for people with other things to do)

Color is an important source of biological information in fields ranging from disease ecology to sexual selection. Despite its importance, most metrics for color are restricted to point measurements. Methods for moving beyond point measurements rely on color maps, where every pixel in an image is assigned to one of a set of discrete color classes (color segmentation). Manual methods for color segmentation are slow and subjective, while existing automated methods often fail due to biological variation in pattern, technical variation in images, and poor scalability for batch clustering. As a result, color segmentation is the common bottleneck step for a majority of existing downstream analyses. Here we present recolorize, an R package for color segmentation that succeeds in many cases where existing methods fail. Recolorize has three major components: (1) an effective two-part clustering algorithm where color distributions are binned and combined according to perceived similarity in a frequency-independent manner; (2) a toolkit for minor manual adjustments to automatic output where needed; and (3) flexible export options. This paper illustrates how to use recolorize and compares it to existing methods, including examples where we segment formerly intractable images, and demonstrates the downstream use of methods that rely on color maps.

bioinformatics↗

bioRxiv2021

Evidence for a selective link between cooperation and individual recognition

The ability to recognize and discriminate among others is a frequent assumption of models of the evolution of cooperative behavior. At the same time, cooperative behavior has been proposed as a selective agent favoring the evolution of individual recognition abilities. While theory predicts that recognition and cooperation may co-evolve, data linking recognition abilities and cooperative behavior with fitness or evidence of selection are elusive. Here, we provide evidence of a fitness link between individual recognition and cooperation in the paper wasp Polistes fuscatus. Nest founding females in northern populations frequently form cooperative multiple foundress nests and possess highly variable facial patterns that mediate individual recognition. We describe a dearth of cooperative nesting, low phenotypic diversity, and a lack of individual recognition in southern populations. In a common garden experiment, northern co-foundress associations successfully reared offspring while all cooperative southern groups failed to rear any offspring, suggesting a fitness link between individual recognition and successful cooperation. Consistent with a selective link between individual recognition and cooperation, we find that rates of cooperative co-nesting correlate with identity-signaling color pattern diversity across the species range. Moreover, genomic evidence of recent positive selection on cognition loci likely to mediate individual recognition is substantially stronger in northern compared to southern P. fuscatus populations. Collectively, these data suggest that individual recognition and cooperative nesting behavior have co-evolved in P. fuscatus because recognition helps mediate conflict among co-nesting foundresses. This work provides evidence of a specific cognitive phenotype under selection because of social interactions, supporting the idea that social behavior can be a key driver of cognitive evolution.

animal behavior and cognition↗