Unexpected benefits from food competitors | Max Planck Society

During spawning, tobacco hawks adopt beetles that compete for food to protect themselves from parasitic wasps.

A research team from the Max Planck Institute for Chemical Ecology has found that female tobacco enthusiasts have an unusual preference for thorny apple plants, which are already infested with leaf beetles when they lay eggs. Beetles and their larvae actually compete with tobacco hawk caterpillars for food. Plants infested with beetles emit a strange odor containing a substance called alpha-cobain and are highly attractive to tobacco enthusiasts. Despite the food competition, caterpillars benefit from selecting such host plants because they are better protected from parasitic wasps and avoid plants that are a nuisance to beetles. The researchers were able to identify the odor receptor of tobacco enthusiasts that controls this behavior.

By selecting the best spawning site, many insects set the path for the best growth of their offspring: there must be adequate food, and the larvae hatching from eggs must be as safe as possible from pathogens and predators.

In a previous study, a research team led by Marcus Nadon and Bill Hanson Department of Evolutionary Neurology It can already be demonstrated that tobacco enthusiasts avoid laying eggs on plants. “So they want to avoid food competition. Therefore, we asked ourselves whether moths avoid plants that are susceptible to other plant pests,” first author Jin Zhang summarizes the research question in the current study.

Beetle-infested moths

Behavioral experiments with thorn apple plants Tadura WrightThey belong to the Colorado beetle genus daturaphila motto Infectious, but gave completely unexpected results: it is obvious that even female tobacco hawks prefer to lay their eggs there, compared to plants that are not affected by beetles. “Honestly, we were a little disappointed at first because we expected the experiments to confirm our initial hypothesis that egg-laying female hawks avoid food competitors. However, in our case, the unexpected result was abrupt. We also found that parasitic wasps, which use plant odors to detect beetles, are less effective at tracking tobacco caterpillar caterpillars in beetle-infested plants, ”explains research leader Marcus Gnaton.

It is not always possible to avoid all the threats in nature, but at the same time choose a place with plenty of food. Studies show that 90 percent of tobacco hawk caterpillars come from wasps. Codicia Congregata Be parasitic. This parasitic wasp species lays its eggs on caterpillars and transmits germs. The parasitic caterpillars eventually die and the wasp hatches.

Affected plants have a distinctive odor

Researchers have used this knowledge to study the behavior of tobacco enthusiasts, who initially seemed strange. They examined the odor of thorn apple plants attacked by Colorado beetles and compared them to non-infectious control plants. After all, there was an extraordinary increase in the meaning of alpha-cobain in the fragrant flower of plants.

The next question the team answered was how moths perceive and process this odor. Since tobacco enthusiasts have about 70 alfactory receptors, they may be candidates for detecting alpha cobain, which can be very time consuming to test all candidates individually. In contrast, the combination of complex molecular biological methods helped to reduce the number of potential alfactory receptors from approximately 70 to about 6, and eventually Or35 was involved in egg selection and activated by alpha cobain.

The researchers also tested the odor-controlled behavior of parasitic wasps. Tests of wasps choosing between two scents, on the one hand, show preference Codicia Congregata For the smell of caterpillar-eating plants. On the other hand, they also showed that wasps avoid the smell of plants affected by Colorado beetles. These results can only be confirmed by behavioral tests in a testing tent where thorn apple plants are infested with tobacco hawks or tobacco hawks and Colorado beetles only.

Cost benefit analysis

Although caterpillars of tobacco hawks do not grow on beetle-infested plants as well as non-infected plants, female moths accept this shortcoming when laying eggs because the benefit of protection against parasitic wasps is obvious. This cost-benefit analysis, also known as “trade”, plays an insignificant role in ecological interactions. “Our conclusions show that simple explanations are often inadequate in nature. Tobacco enthusiasts should not only consider whether a plant is suitable for their offspring as food, but also consider whether there are already potential competitors and whether their presence helps to avoid the dangers of predators,” says Bill Johnson.

Further studies will show why thorn apple plants emit different odors, depending on which insects eat them. Both caterpillars of tobacco hawks and larvae of the Colorado beetle species daturaphila motto Chewing insects cause similar damage to plant tissues. Presumably, microorganisms play a role in the oral secretions of animals. For example, intermediate approaches focusing on the role of microorganisms in these complex interactions help to discover other striking features of different interactions between organisms.