Predicting when plants face extinction threat

June 18, 2012 By Iqbal Pittalwala
A field experiment using the yellowflower tarweed (Holocarpha virgata), shown here growing at the study site, the Donald and Sylvia McLaughlin Reserve in central California, confirms key predictions of the model. Credit: C. Essenberg, UC Riverside.

( -- Drawn to dense stands of wildflowers in search of food, bees and other pollinators carry pollen between plants and provide a vital service for the survival of many plant species.

But human activities can disrupt this mutually-beneficial relationship. , , and the spread of exotic species can all transform previously abundant plant populations into sparse remnants incapable of attracting pollinators and doomed to spiral into extinction.

Carla Essenberg, a Ph.D. candidate in the Department of Biology at the University of California, Riverside, has developed a to predict when plants are at risk of losing their pollinators, which could guide decisions that help prevent extinctions of wildflower species.

Assuming only that flower-visiting insects attempt as quickly as possible to harvest energy in the form of , the model predicts key threshold densities below which plants become much less attractive to pollinators.

Developed at UC Riverside, Essenberg’s model shows that plant species with widely-scattered, inconspicuous flowers are the most likely to lose their ability to attract pollinators as their densities decline.

“This could be a problem because with these traits probably won’t be very attractive to pollinators in the first place and can ill afford to lose the few pollinator visits they normally receive,” said Essenberg, who studied music and philosophy during her undergraduate days at St. Olaf College, Minn., before turning her attention to pollination ecology at UCR.

The model first obtains several estimates: how quickly the pollinators travel between flowers, how much time they need to extract pollen and nectar from a flower, how large their foraging range is, what the flower density outside of the population being studied is, and how dense the pollinator population is.  With these estimates, the model then generates a plot showing the relationship between flower density and per-flower visitation rates.  Typically, predicted visitation rates drop very rapidly towards low densities, whereas they respond less to flower density at higher densities.

“The model’s predictions provide a starting point for field studies investigating the factors that put at risk of reproductive failures and ultimately extinction,” Essenberg said.

Study results appear in the August issue of the American Naturalist.

Over the past few hundred years, human activities have increased species extinction rates by as much as a thousand times their previous levels.

“With resources available for rescuing threatened species stretched thin, predicting which species are in the greatest danger could play a vital role in conserving the rich biodiversity we have today for our children and grandchildren to enjoy,” Essenberg said.

Explore further: Wild plants are good for pollinators

Related Stories

Wild plants are good for pollinators

October 6, 2011

A new study has shown that encouraging strips of wild plants at the edges of fields is important for supporting bees and other important pollinators.

Biodiversity can promote survival on a warming planet

November 4, 2011

Whether a species can evolve to survive climate change may depend on the biodiversity of its ecological community, according to a new mathematical model that simulates the effect of climate change on plants and pollinators.

New research explains orchids' sexual trickery

December 17, 2009

A new study reveals the reason why orchids use sexual trickery to lure insect pollinators. The study, published in the January issue of The American Naturalist, finds that sexual deception in orchids leads to a more efficient ...

Probing Question: Why are flowers beautiful?

January 24, 2008

In the 1930s, American artist Georgia O'Keefe wrote: "What is my experience of the flower if it is not color?" O'Keefe is best known for her vibrantly colorful close-ups of petals and stamens on large canvases.

Recommended for you

Stressed-out meerkats less likely to help group

September 22, 2017

Dominant female meerkats use aggression to keep subordinates from breeding, but a new study finds this negative behavior also can result in the latter becoming less willing to help within the group.

Why poison frogs don't poison themselves

September 21, 2017

Don't let their appearance fool you: Thimble-sized, dappled in cheerful colors and squishy, poison frogs in fact harbor some of the most potent neurotoxins we know. With a new paper published in the journal Science, scientists ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.