A team of researchers from the University of Zurich has found that plants benefit from a greater variety of interactions with pollinators and herbivores. Plants that are pollinated by insects and need to defend themselves against herbivores have evolved to be better adapted to different soil types.
Plants obtain nutrients and water from the soil. Because different soil types differ in their chemical and physical composition, plants must adapt their physiology to optimize this process on different soil types.
This evolutionary process leads to the formation of ecotypes, i.e. locally adapted ‘plant varieties’ that differ slightly in appearance and may no longer be easily interbred. This latter effect is considered the first step toward the formation of separate species. The adaptation of crops to local soil types is also crucial for agricultural productivity.
Experiment with bumblebees and aphids
A team of researchers led by biologist Florian Schiestl from the Department of Systematic and Evolutionary Botany at the University of Zurich has now discovered that plants’ interactions with pollinators and herbivorous insects influence their adaptation to soil types and thus the formation of ecotypes. In a two-year experiment, approximately 800 turnip plants were grown on different soil types in a greenhouse for 10 generations. One group was pollinated by bumblebees, the other by hand; in addition, the plants were grown with and without aphids (as herbivores).
At the end of the evolutionary experiment, the researchers examined to what extent the plants on the two soil types differed in shape and composition and how well they had adapted to the soil. In terms of shape, it turned out that only the plants pollinated by bumblebees showed clear differences between the soil types, while the hand-pollinated plant groups remained largely the same.
Plants pollinated by bumblebees adapt best
In fact, when it comes to adaptation to soil types, after the two years of experimental evolution, the researchers only found significant adaptation in bumblebee-pollinated plants with aphids, while no significant adaptation to soil types was observed in the other groups.
The study also identified several genes that may play a crucial role in this adaptation process. The results show that biotic interactions can strongly influence the ability of plants to adapt to abiotic factors and that adaptation is most efficient when plants are exposed to a variety of interactions.
