Different plant species are competing with each other to win the attention of birds, bees and… Different plant species are competing with each other to win the attention of birds, bees and other pollinators in biodiversity hot spots such as rainforests.

Three Pitt researchers participated in a study that found that plants outnumber pollinators in these hot spots, and this could cause extinction of certain plant species as well as problems for humans.

Tia-Lynn Ashman, associate professor of biological sciences at Pitt, worked on the project along with two former biology graduate students, Janette A. Steets and Tiffany Knight. Steets is currently a postdoctoral fellow at the University of Alaska Fairbanks, and Knight is currently an assistant professor at Washington University in St. Louis.

Since 2002, the research group has reviewed more than 1,000 published pollen limitation studies.

They have found that in areas where there are many different plant species, such as the jungles of South America and Southeast Asia, plants have low pollination success. Therefore, the plants are not reproducing as much as they should be.

There are a few speculations as to why there is a decline in these highly populated areas, according to Steets.

“Habitat destruction is occurring at alarming rates in the tropics,” Steets said. “Our study identifies an interesting pattern, plants located in biodiverse areas are more pollen limited than those in less diverse regions.”

Steets said that they don’t know if this pattern is the result of habitat destruction – which would cause more competition in the regions – or if the pattern is a naturally occurring phenomenon that happens in such areas where plant species are constantly faced with new competitors and cannot evolve rapidly enough.

Since there are many different plant species, including new competitors, in these dense areas, pollinators often have to fly long distances to deliver pollen from one plant to another of the same species.

Knight explained that plants compete to gain the attention of the pollinators.

“Plants that have showy flowers or offer more nectar and pollen rewards may ‘steal’ pollinators away from less rewarding species,” Knight said. “What our study does [show] is that competition for pollinators among different plant species might be important at a more regional spatial scale. It might explain global patterns of pollen limitation.”

Pollen limitation lowers seed production, and some plants are heading toward extinction, and the things that people need from plants may begin to disappear along with plant diversity.

Plants in these regions provide people with medicine, food and nutrient cycling – the exchange of oxygen and carbon dioxide – for example.

Ashman said that attention must be focused on ways to preserve pollinators that live in these areas. She and Knight also noted that people should try to avoid development of these areas.

“Human influences also cause pollen limitation, and we should try to avoid making these disturbances that might further exacerbate the pollen limitation,” Knight said.

The research was an international effort. The leader of the project was Jana Vamosi, of the University of Calgary, and another author was Martin Burd, who is from Australia. The data that they reviewed was taken from studies that were conducted by researchers from Asia, Africa, Australia, North and South America and Europe.

The same research group is doing more studies focused on causes and consequences of pollen limitation.