Communication depends on reliability. Yet, the existence of stable honest signalling presents an evolutionary puzzle. Why should animals signal honestly in the face of a conflict of interest? While students of animal signalling have offered several theoretical answers to this puzzle, the most widely studied model, commonly called the 'handicap principle', postulates that the costs of signals stabilize honesty. This model is the motivating force behind an enormous research enterprise that explores signal costs-whether they are physiological, immunological, neural, developmental or caloric. While there can be no question that many signals are costly, we lack definitive experimental evidence demonstrating that costs stabilize honesty. This study presents a laboratory signalling game using blue jays (Cyanocitta cristata) that provides, to our knowledge, the first experimental evidence showing honesty persists when costs are high and disappears when costs are low.

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.

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ABSTRACT.-Urban-adapter species facultatively exploit human-subsidized resources in the urban and suburban matrix. We used the woodchuck (Marmota monax) to study how aspects of autecology in an urban-adapter can vary across a gradient of urbanization. We captured and monitored woodchucks by radiotelemetry in southern Illinois from summer 2007 to spring 2009. We captured 47 woodchucks (19 adults, 19 yearlings, 8 young-of-the-year) during the active seasons, and implanted radiotransmitters in 17 adults and 3 yearlings (13 F, 7 M). Overall annual survival was estimated to be 0.76 6 0.12, with three confirmed mortalities during the study period. Survival and home-range size did not vary by % urban landcover in a buffer surrounding an individual's home range. Habitat-selection analyses indicated that rural edge was the highest-ranked habitat at the home-range scale, whereas urban cover (specifically, developed areas with human structures) was most highly ranked at the withinhome-range scale. Body condition was negatively related to % urban landcover. Overall, our findings indicated no clear relationship between woodchuck ecology and urbanization level within our study area. However, our data on body condition and adipose composition, although preliminary, suggested a possible mechanism for variation in overwinter survival across the urban-rural gradient.