Search

Paper wasps are a model system for the study of social evolution due to a high degree of inter- and intraspecific variation in cooperation, aggression, and visual signals of social status. Increasing the taxonomic coverage of genomic resources for this diverse clade will aid comparative genomic approaches for testing predictions about the molecular basis of social evolution. Here, we provide draft genome assemblies for two well-studied species of paper wasps, Polistes exclamans and Mischocyttarus mexicanus. The P. exclamans genome assembly is 221.5 Mb in length with a scaffold N50 of 4.11 Mb. The M. mexicanus genome assembly is 227 Mb in length with a scaffold N50 of 1.1 Mb. Genomes have low repeat content (9.54–10.75%) and low GC content (32.06–32.4%), typical of other social hymenopteran genomes. The DNA methyltransferase gene, Dnmt3  , was lost early in the evolution of Polistinae. We identified a second independent loss of Dnmt3 within hornets (genus: Vespa). [ABSTRACT FROM AUTHOR]

Why workers forfeit direct reproduction is a crucial question in eusocial evolution. Worker reproduction provides an excellent opportunity to understand the mechanism of kin conflict resolution between the queen and workers. We evaluated behavioral and physiological differences among females in the paper wasp Polistes chinensis antennalis to examine why some workers reproduce under queenright conditions. Reproductive workers were old and foraged less early in the season; their cuticular hydrocarbon (CHC) profiles overlapped with those of queens but were significantly different. The distinct CHC profile of the eggs of the queen likely represented a cue for policing against those by workers. Juvenile hormone (JH) and dopamine seemed to be associated with gonadotropic function, and the JH level of reproductive workers was similar to that of the queen. The high JH level of reproductive workers likely facilitated their reproduction even under queenright conditions. Gene expression levels of the queen and reproductive workers differed only in vitellogenin. These results suggest that worker reproduction is facilitated by an increase in JH level; however, CHC is not a fertility-linked signal, but a queen-linked signal; consequently, reproductive workers without a queen-linked signal might be allowed to stay within the colony. [ABSTRACT FROM AUTHOR]

Paper wasps negotiate over help using indicators of demand. Animal societies are composed of individuals whose genetic interests are often opposed. We conducted experiments on a cooperative paper wasp which reveal the behavioural rules by which group members settle these conflicts.Recent theory and empirical studies of avian biparental systems suggest that animals resolve conflict over parental care via a process of behavioral negotiation or “rules for responding.” Less is known, however, about whether negotiation over helping effort occurs in cooperatively breeding animal societies or whether behavioral negotiation requires a relatively large brain. In this study, we tested whether negotiation over help occurs in a social insect, the paper wasp Polistes dominulus, by recording individual responses to both observed and experimentally induced foraging returns by other group members. In our experiments, we manipulated food delivery to the nest in 2 ways: 1) by catching departing foragers and giving them larval food to take back to the nest and 2) by giving larval food directly to wasps on the nest, which they then fed to larvae, so increasing food delivery independently of helper effort. We found no evidence from Experiment 1 that helpers adjusted their own foraging effort according to the foraging effort of other group members. However, when food was provided directly to the nest, wasps did respond by reducing their own foraging effort. One interpretation of this result is that paper wasp helpers adjust their helping effort according to the level of offspring need rather than the work rate of other helpers. Negotiation based on indicators of demand rather than work rate is a likely mechanism to resolve conflict over investment in teams where helpers cannot observe each other’s work rate directly, as is commonly the case in insect and vertebrate societies. [ABSTRACT FROM PUBLISHER]

Identifying broad-scale evolutionary processes that maintain phenotypic polymorphisms has been a major goal of modern evolutionary biology. There are numerous mechanisms, such as negative frequency-dependent selection, that may maintain polymorphisms, although it is unknown which mechanisms are prominent in nature. Traits used for individual recognition are strikingly variable and have evolved independently in numerous lineages, providing an excellent model to investigate which factors maintain ecologically relevant phenotypic polymorphisms. Theoretical models suggest that individuals may benefit by advertising their identities with distinctive, recognizable phenotypes. Here, we test the benefits of advertising one's identity with a distinctive phenotype. We manipulated the appearance of Polistes fuscatus paper wasp groups so that three individuals had the same appearance and one individual had a unique, easily recognizable appearance. We found that individuals with distinctive appearances received less aggression than individuals with nondistinctive appearances. Therefore, individuals benefit by advertising their identity with a unique phenotype. Our results provide a potential mechanism through which negative frequency-dependent selection may maintain the polymorphic identity signals in P. fuscatus. Given that recognition is important for many social interactions, selection for distinctive identity signals may be an underappreciated and widespread mechanism underlying the evolution of phenotypic polymorphisms in social taxa. [ABSTRACT FROM AUTHOR]