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Flower evolution is influenced by the animals that visit

Flower evolution seems to be influenced by the various animals that visit, according to a new study from the University of Tsukuba. The researchers have proposed a new theory that trade-offs caused by different visitors play a central role in shaping floral diversity.

When it comes to interactions between animals and flowers, some visitors are beneficial, like pollinators, while others can be detrimental. As a result, different selection pressures influence flower traits such as scent or color. 

“On the basis of this theory, you’d expect that flowers would mostly be visited by one particular group of pollinators,” said study lead author Professor Kazuharu Ohashi. “But flowers often host many different visitors at the same time and flowers appear to meet the needs of multiple visitors. The question we wanted to answer is how this happens in nature.”

In the case where a scent attracts one pollinator but deters another, the flower would attempt to accommodate the best pollinator. 

For example, diurnal bees and nocturnal moths can both pollinate goat willow, yet they prefer different smells. The researchers explained that balancing the demands of multiple visitors involves trade-offs.

The experts developed a conceptual framework to examine different types of trade-offs, as well as how flower evolution may be affected. Next, the team analyzed relevant studies to determine whether the research supported the proposed framework.

The researchers discovered a variety of strategies for mitigating trade-offs. In the case of goat willow, flowers produce different scents during the day and night, and therefore attract both pollinators. Furthermore, floral color can change to attract both bees and flies. 

All of the strategies that were mentioned by the researchers involved acquiring novel combinations of traits to attract, or deter, different visitors.

“Most flowers are ecologically generalized and the assumption to date has been that this is a suboptimal solution,” said Professor Ohashi. “But our findings suggest that interactions with multiple animals can actually be optimized by minimizing trade-offs in various ways, and such evolutionary processes may have enriched the diversity of flowers.”

The researchers predict that future studies will find that the structure of flower-visitor communities and the associated trade-offs have played critical roles in flower evolution.

“Identifying convergent adaptations to particular community contexts may help us to understand better the evolutionary link between diverse floral phenotypes and their visitors.’

The study is published in the journal Biological Reviews.

By Chrissy Sexton, Staff Writer

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