Insect Interactions Speed Up Plant Evolution

Researchers at the University of Zurich have found that plants derive greater benefits from diverse interactions with pollinators and herbivores.

Plants that are pollinated by insects and must defend themselves against herbivores have evolved to be better adapted to various types of soil.

Plants draw water and nutrients from the soil. Because the chemical and physical composition of different soil types vary, plants must modify their physiology to maximize this process on a variety of soil types.

Ecotypes, or locally adapted "plant breeds," are created as a result of this evolutionary process. The breeds have slightly different appearances and may become difficult to crossbreed. The latter effect is thought to be the precursor to the emergence of distinct species. Crop adaptation to regional soil types is also essential for high agricultural yields.

Experiment with Bumblebees and Aphids

According to research led by biologist Florian Schiestl of the University of Zurich's Department of Systematic and Evolutionary Botany, the interaction between plants and herbivorous insects, as well as the soil types to which they adapt, affects the formation of ecotypes. During a two-year experiment, about 800 swede plants were cultivated over 10 generations on various soil types in a greenhouse. Aphids were used as herbivores in the cultivation of the plants, and bumblebees and humans pollinated separate groups of plants.

Following the evolutionary experiment, the scientists examined the degree of shape and compositional variation and soil adaptation of the plants on the two types of soil. The plants that were hand-pollinated stayed mostly the same, but only the plants pollinated by bumblebees displayed distinct variations in shape between the soil types.

Plants Pollinated by Bumblebees Adapt Best

After two years of experimental evolution, the researchers only observed significant adaptation to soil types in bumblebee-pollinated plants with aphids; no significant adaptation to soil types was observed in the other groups.

The findings demonstrate that biotic interactions can significantly impact plants' capacity to respond to abiotic stimuli and that plants respond most effectively to a range of interactions.