Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Instant Evolution in Whiteflies: Just Add Bacteria

In a case of rapid evolution, bacteria have been found to give whiteflies – crop-damaging insects of global importance – an edge over their uninfected peers, new research from the University of Arizona suggests.

In just six years, bacteria in the genus Rickettsia spread through a population of the sweet potato whitefly (Bemisia tabaci), an invasive pest of global importance. Infected insects lay more eggs, develop faster and are more likely to survive to adulthood compared to their uninfected peers. The discoveries were made by a University of Arizona-led team of scientists and are published in the April 8 issue of the journal Science.

"It's instant evolution," said Molly Hunter, a professor of entomology in the UA's College of Agriculture and Life Sciences and the study's principal investigator. "Our lab studies suggest that these bacteria can transform an insect population over a very short time."

"It is not uncommon to find a microbe providing some benefits to their hosts, but the magnitude of fitness benefits we found is unusual," she added.

In addition to the observed evolutionary advantages – which biologists call fitness benefits – Hunter's team discovered that the bacteria manipulate the sex ratio of the whiteflies' offspring by causing more females to be born than males.

According to Hunter, the bacteria are transmitted only through the maternal lineage (from mother to offspring). Therefore, it is beneficial for them to make sure more female than male whiteflies are born.

"However, we don't know how they're doing that yet," she said.

Anna Himler, a postdoctoral research associate in Hunter's lab and the lead author on the research paper, said her team was most surprised by the speed with which the bacteria moved through the whitefly population.

In 2000, the researchers found Rickettsia in only 1 percent of the whiteflies in Arizona. In 2003, the microbes had spread through half of the population, and today, almost all whiteflies in Arizona contain the bacterium.

Whiteflies come in many different species and variants within species called biotypes. Of those, none are considered as detrimental to agriculture as the "B Biotype" of the sweet potato whitefly, which originated in the Mediterranean.

Contrary to what their name implies, whiteflies belong to an order of insects known as Hemiptera and are related to aphids and true bugs. Like their kin, they puncture their host plants and suck out the sugary sap. In addition to stripping the plant of nutrients, larvae and adults produce copious amounts of honeydew, which attracts mold and leads to damage of the leaves. Finally, whiteflies transmit plant viruses; in the case of the sweet potato whitefly, more than a hundred different kinds.

Compared to the vast majority of whiteflies, which are highly specialized and feed only on particular host plants, the sweet potato whitefly feeds on more than 600 host plants, which means it can move from one plant to another through the seasons.

"Here in Arizona, it probably starts out on weeds in the spring, and then moves on to melons, and when melons are done, it moves in big numbers onto cotton and feeds on that all summer long," Hunter explained. "In the fall, it moves on to vegetables, and so it just keeps going."

What whiteflies lack in body size – they are about one-sixteenth of an inch long – they make up for in numbers. Whiteflies can colonize a host plant in large numbers and blanket leaves with larvae and sticky honeydew in a short time."

"In the late 1980s and early 1990s, when this new biotype arrived in the Southwest, the population just exploded," Hunter said. "Sometimes you could see clouds of whiteflies in the air, gumming up windshields. With integrated pest management practices, many developed by colleagues here at the UA, their impact has decreased tremendously, but they still are the worst pest in Arizona's cotton industry. If it wasn't for whiteflies, farmers would be spraying cotton a lot less."

The team is now trying to explain how Rickettsia increases whitefly fitness. In one conceivable scenario, the bacteria might turn down the plant defenses in an effort to make it easier for the whitefly to feed on the plant.

Himler said that because studies done elsewhere suggested fitness differences were not important, her team initially believed that in order for the microbes to spread so rapidly through the population, the whiteflies must pass them on through horizontal transfer (from individual to individual) rather than through vertical transfer (from mother to offspring).

"So we did this big horizontal transmission experiment but found almost nothing. At the same time, we saw these incredible differences between the Rickettsia-positive and Rickettsia-negative whitefly cultures. In evolution, fitness is the money. So I just saved a couple of leaves from my plants from the horizontal transmission experiment and thought, let's look at the offspring. Even though I only had a few leaves, the effect was strong. We found many more offspring coming from the Rickettsia-positive plants than from the control plants."

"Rickettsia-infected whiteflies lay more eggs, more of those eggs survive, and there is the reproductive manipulation toward producing more female than male offspring. These effects are not unheard of, but the strength that we found here is unusual."

According to Hunter, the interaction between host and bacteria is a tug-of-war between a positive and negative effect.

"In general, taking the sex ratio control away from the host is not a good thing for the host," she said. There is a reason why most living organisms have roughly equal proportions of sexes. If there were more females, then any individual producing more males would produce more progeny. This is one of the reasons a one-to-one sex ratio is really common in nature."

The team believes that discovering how profoundly and how fast microbes can change a population of a pest of global importance has implications for pest management strategies.

"It would be interesting to see if by having a microbe that has this big effect in one direction, if you could make it so that it has an effect in the other direction, to help control the pest," Hunter said. "Could we use symbionts in a way to make things less of a problem, to manage pest populations in a more sustainable way?"

The report,"Rapid Spread of a Bacterial Symbiont in an Invasive Whitefly Is Driven by Fitness Benefits and Female Bias," is online at:


Martha (Molly) S. Hunter
Department of Entomology
The University of Arizona
Daniel Stolte
University Communications
The University of Arizona

Daniel Stolte | University of Arizona
Further information:

More articles from Life Sciences:

nachricht North and South Cooperation to Combat Tuberculosis
22.03.2018 | Universität Zürich

nachricht Researchers Discover New Anti-Cancer Protein
22.03.2018 | Universität Basel

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Researchers Discover New Anti-Cancer Protein

An international team of researchers has discovered a new anti-cancer protein. The protein, called LHPP, prevents the uncontrolled proliferation of cancer cells in the liver. The researchers led by Prof. Michael N. Hall from the Biozentrum, University of Basel, report in “Nature” that LHPP can also serve as a biomarker for the diagnosis and prognosis of liver cancer.

The incidence of liver cancer, also known as hepatocellular carcinoma, is steadily increasing. In the last twenty years, the number of cases has almost doubled...

Im Focus: Researchers at Fraunhofer monitor re-entry of Chinese space station Tiangong-1

In just a few weeks from now, the Chinese space station Tiangong-1 will re-enter the Earth's atmosphere where it will to a large extent burn up. It is possible that some debris will reach the Earth's surface. Tiangong-1 is orbiting the Earth uncontrolled at a speed of approx. 29,000 km/h.Currently the prognosis relating to the time of impact currently lies within a window of several days. The scientists at Fraunhofer FHR have already been monitoring Tiangong-1 for a number of weeks with their TIRA system, one of the most powerful space observation radars in the world, with a view to supporting the German Space Situational Awareness Center and the ESA with their re-entry forecasts.

Following the loss of radio contact with Tiangong-1 in 2016 and due to the low orbital height, it is now inevitable that the Chinese space station will...

Im Focus: Alliance „OLED Licht Forum“ – Key partner for OLED lighting solutions

Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology FEP, provider of research and development services for OLED lighting solutions, announces the founding of the “OLED Licht Forum” and presents latest OLED design and lighting solutions during light+building, from March 18th – 23rd, 2018 in Frankfurt a.M./Germany, at booth no. F91 in Hall 4.0.

They are united in their passion for OLED (organic light emitting diodes) lighting with all of its unique facets and application possibilities. Thus experts in...

Im Focus: Mars' oceans formed early, possibly aided by massive volcanic eruptions

Oceans formed before Tharsis and evolved together, shaping climate history of Mars

A new scenario seeking to explain how Mars' putative oceans came and went over the last 4 billion years implies that the oceans formed several hundred million...

Im Focus: Tiny implants for cells are functional in vivo

For the first time, an interdisciplinary team from the University of Basel has succeeded in integrating artificial organelles into the cells of live zebrafish embryos. This innovative approach using artificial organelles as cellular implants offers new potential in treating a range of diseases, as the authors report in an article published in Nature Communications.

In the cells of higher organisms, organelles such as the nucleus or mitochondria perform a range of complex functions necessary for life. In the networks of...

All Focus news of the innovation-report >>>



Industry & Economy
Event News

Virtual reality conference comes to Reutlingen

19.03.2018 | Event News

Ultrafast Wireless and Chip Design at the DATE Conference in Dresden

16.03.2018 | Event News

International Tinnitus Conference of the Tinnitus Research Initiative in Regensburg

13.03.2018 | Event News

Latest News

Modular safety concept increases flexibility in plant conversion

22.03.2018 | Trade Fair News

New interactive map shows climate change everywhere in world

22.03.2018 | Earth Sciences

New technologies and computing power to help strengthen population data

22.03.2018 | Earth Sciences

Science & Research
Overview of more VideoLinks >>>