Bees, ants and beings are considered social animals that selflessly work for their state – but only their own. However, some species of field wasp not only support their own colony, but also their more distant relatives, as researchers have observed. According to this, the workers also babysit larvae in neighboring nests. In doing so, they invest in the part of the genes that these “cousins” carry.
Animals naturally have the instinct to reproduce and thus pass on their genes. At first glance, the states of ants, bees and co. Seem to contradict this principle. Because in these eusocial communities only the queen lays eggs and the workers are sterile. But from an evolutionary point of view, this extreme altruism is advantageous. Because the queen and workers are sisters, all young animals carry a large part of the genes of every worker.
Why do wasps help in other nests?
However, in some social insects, altruism extends beyond the closest kinship, as researchers have now observed Neotropical field wasps of the genus Polistes. A large part of the workers help not only in their own colony, but also with the rearing of broods in neighboring nests. Researchers working with Patrick Kennedy from the University of Bristol have now analyzed how this behavior can be evolutionarily advantageous. “The fact that wood wasps are helping other colonies in Central and South America is really strange considering that most wasps, ants, and bees are extremely hostile to outsiders,” said Kennedy.
Scientists believe that there are several possible explanations for this behavior. The neighborhood help could increase the chance that the wasp workers will be helped themselves at a later point in time. On the other hand, investing in several colonies with less closely related conspecifics could also be an evolutionary advantage if a nest is destroyed by predators, for example. In addition, the researchers hypothesized that with a large number of workers in their own nest, some become “useless” and therefore help in less related colonies that require more care.
To test their hypotheses, the research team observed 20,000 wasp larvae and their caring workers of the species Polistes canadensis in various colonies that lived in the vicinity of the Panama Canal. The scientists compared the behavior of the workers in nests of different sizes and combined their field observations with mathematical models in which they documented the development of the larvae in the brood cells.
Over-supply of workers
It was shown that the more colony members in their own nest increased, the more workers left their colony and helped out in a foreign nest. The researchers attribute this to the fact that there is actually an oversupply of help in large colonies and that individual wasps are not needed there for rearing. “Our results show that worker wasps can be eliminated at home,” concludes Kennedy. “A wasp in a colony with few larvae, but many other workers becomes almost useless: It is best if it nurses the larvae of other relatives.” Then, overall, more wasp colonies survive and thus the less related offspring of the workers in the others Nests.
“By helping more distant relatives who are more needy, live next door, and have fewer carers, workers can pass on more copies of their genes overall,” said Kennedy’s colleague Andy Radford. “These wasps can act like wealthy family members helping their second cousins,” added Kennedy. “When you can’t do much to help your immediate family, you can turn to the extended family.” So these field wasps indirectly increase their fitness by investing in the offspring that carry fewer of their genes. “We believe that similar principles of diminishing utility could explain the seemingly paradoxical behaviors of altruism in many other social animals,” speculates Radford.
Source: University of Bristol, Article: Nature Ecology & Evolution, doi: s41559-020-01382-z