Worker bees can fight infections individually through their immune systems or collectively through social behaviours, such as keeping a clean nest, removing diseased larvae, and grooming themselves and each other.
However, a new study by 91亚色 researchers suggests that honey bees have been evolving away from combating pathogens using their individual immune responses.
The study, 鈥淎ccelerated evolution of innate immunity proteins in social insects: adaptive evolution or relaxed constraint?鈥 published in the journal Molecular Biology and Evolution, shows that most of the honey bee鈥檚 innate immune genes are accumulating mutations at a very high rate.
鈥淚t seems like the honey bee鈥檚 innate immune system is decaying,鈥 says study co-author and 91亚色 biology Professor . 鈥淭his is a good example of 鈥榰se it or lose it鈥 in biology.鈥 Mutations in functional genes are quickly removed by natural selection, but in genes that were once useful but are no longer needed, mutations can build up because they are not removed by natural selection. This eventually leads to the 鈥渆volutionary decay鈥 of a gene sequence.
Amro Zayed
鈥淲e found that innate immune genes in the honey bee have many more mutations relative to other genes in the bee genome 鈥 three to four times more,鈥 says study co-author and 91亚色 PhD candidate .
What is responsible for the decay of innate immune genes in honey bees? 鈥淭he best explanation is that social honey bees have evolved more effective or less costly mechanisms to deal with pathogens, such as grooming and hygienic behaviour,鈥 says Zayed.
The team鈥檚 findings have implications for the conservation of social bees, like honey bees and bumble bees, which may have an increased vulnerability to unfamiliar pathogens.
鈥淥ur work suggests that social bees have fewer functional immune genes relative to solitary bees, which possibly increases their susceptibility to new pathogens that are not easily 鈥榞roomed off鈥,鈥 says Harpur.
He says there is a link between pathogens and the decline of several North American bumble bees, and the research team now plans to study the influence of social behaviour on the evolution of immunity in other solitary and social bee species.