Information theory has explained the arms race with insects and plants

The redundancy range of volatile organic compounds (VOCS)emitted by plants, can be explained from the standpoint of information theory, reported in Science. Insects analyze olfactory signals and capitalize on them, knowing which plants you can eat, and the plants are trying to create around these signals and information noise, highlighting all of the new LOS, the value of which arthropods is unclear.

Long known that plants and insects exchange information, mostly represented by chemical signals — volatile organic compounds that you can smell. Some of these compounds repel insects, some drawing them, some poison, some attract predators, these insects are able to eat. However, the majority of data on VOCS and their effect on insects obtained in studies where considered the minimum number of types — for example, one plant and one animal. Work, which would take into account interactions across the whole community, almost none.

Environmentalists from Austria, Mexico, USA and other countries under the leadership of Juan Peng zu (Zu Pengjuan) from the Massachusetts Institute of technology presented a study that analyzed relationships to a variety of types of insects and plants. To do this, they in 2018 conducted field observations in dry tropical forest of the Mexican reserve Camela-Cuixmala. Researchers were interested in the caterpillars of 28 butterfly species and leaves of 20 species of plants. In the air directly surrounding the leaves, looking for volatile organic compounds and compared them with known ones. The scientists also determined, whose caterpillars eat which plants.

The data collected is analyzed from the point of view of information theory. Environmental studies conducted with its use, suggest that the nature of the interaction between the sender and receiver of signals determines the quality of transmitted data. Relatively speaking, organisms will try to give the enemies of the noisy signals that can be interpreted in different ways, and the friendly creatures — an unambiguous signal without interference. Based on this logic, the plants should broadcast herbivorous insects data that are confusing, and insects have to learn to understand them correctly and to isolate important information from the noise.

Zu and colleagues made up of a matrix of relations, volatile organic compounds, and insects, as well as LOS and plants. It turned out that each species of butterfly is associated with a small number of plant species — from 1 to 9. However, one plant produces an average of 26 different VOCS, so the caterpillar of a particular species have to interact with dozens of volatile organic compounds and to understand what information each of them carries. All the authors have identified 56 LOS of biological origin, so it turns out that different species produce similar sets of such connections is likely that insects do not distinguish between the types of scent.

In computer simulations of the relationship of caterpillars and plants, the researchers made changes in the elements of the resulting matrices so that the quality of information transmitted is increased or decreased. They’ve started with options when insects are poorly understood signals of plants (and/or the plants produce quite a bit different VOCS), and variants when the caterpillars are already well identificeret the set of volatile organic compounds. In some cases, considered all views, in some others only some of the studied. It was necessary to test the validity of the hypothesis, since it is known that the sample strongly affects the results of studies of the interaction of organisms.

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