Fewer bees, less plant diversity

In an unexpected twist in Darwin’s survival of the fittest, a research collaboration from Princeton University, USA, and the Swiss Federal Institute of Technology (ETH), Zurich, found that as plants compete for a declining population of visiting pollinators (bees, butterflies, and other insects), they experience population decline and an overall decrease in species diversity.

This goes against ecological theory, which suggests that environmental pressures, such as competition from pollinators, would drive adaptation among plants, making species more diverse, not less.

The research team planted five species of annual flowering plants (including poppies, cornflowers and wild fennel) in a meadow, gradually changing the planting density – which is the number of plants next to each other. Some sections were exposed to normal levels of pollination – by bees (bees, bees, solitary bees), flower flies and butterflies in this case. Other sections were given extra help (literally), with humans physically transferring extra pollen.

Cornflowers in a meadow
A meadow of cornflowers. Credit: Nick Brundle Photography / Getty Images

The researchers found that in situations where plants competed for the attention of bees, flies and butterflies (without human assistance), there was a greater decline in population growth and diversity.

To live as a successful population, plants develop niche differences that interact with the unique adaptations of other plants in a sort of equilibrium or equilibrium system. When this balance is disrupted – when the number of pollinators decreases, for example – the imbalance tends to favor common species over rare species. The reasons for this are many and complicated, but include factors such as the ease with which pollen is collected and dispersed by pollinators, the already inflated number of more common varieties, and the greater likelihood of receiving common pollen from a visiting pollinator.

A plane sprays crops with pesticides
A plane sprays the crops with pesticides. Credit: Don Mason/Getty Images

“Climate change, habitat modification and pesticides are believed to be the main drivers of pollinator decline,” says Christopher Johnson, research scientist and engineer at the University of Washington, USA, and one of the authors of this study. “change the competitive playing field for plants, causing some plant species to go extinct”.

There are some important implications; not just for how we understand ecological evolution in this scenario, but also potentially to feed a growing global population. “Food security is critical for a growing world population – which is also putting increasing pressure on plant and pollinator communities – so it is important to better understand plant pollinator communities and work to conserve them around the world” , explains Johnson.

In the future, we may have engineered pollinators like “RoboBees” that can help plants maintain diversity and population, but for now, it’s worth focusing on conserving natural pollinators. “What I can say about being out in the field, painting plants by hand with a brush is that insect pollinators are very, very good at their jobs, so there is no substitute for healthy, diverse communities of plant pollinators,” he says. Johnson.

For those lucky enough to have a backyard vegetable garden or flower garden, Johnson’s message is simple: “Grow a wide variety of plant species and enjoy the diversity of pollinators that visit your garden.”

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