Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Canceled flights: For monarch butterflies, loss of migration means more disease

30.01.2015

Planting tropical milkweed, available at many garden centers, makes the problem worse

Human activities are disrupting the migration patterns of many species, including monarch butterflies. Some monarchs have stopped migrating to their traditional overwintering sites in Mexico, remaining in the southern U.S. to breed during the winter.


A monarch caterpillar munches on tropical milkweed in a garden at The Landings in Savannah, Ga., in January 2014.

Credit: Dara Satterfield/University of Georgia

A new study by University of Georgia ecologists, just published in the journal Proceedings of the Royal Society B, has found that these sedentary winter-breeding butterflies are at increased risk of disease, a finding that could apply to other migratory species as well. But, for the monarchs at least, there may be a relatively simple solution.

Every year, millions of monarch butterflies travel from breeding grounds in the eastern U.S. and Canada to spend the winter in central Mexico. In recent years, however, their numbers have declined sharply as changing agricultural practices and land use patterns have reduced the availability of milkweed, the plant on which monarchs lay their eggs.

In response, concerned gardeners have started planting milkweed to help replace some of the butterflies' lost breeding habitat. The most readily available commercially grown milkweed sold by garden centers is the exotic species Asclepias curassavica, or tropical milkweed. Monarchs love it, but, according to the study's lead author Dara Satterfield, a doctoral student in the UGA Odum School of Ecology, tropical milkweed does not naturally die back in fall like perennial milkweeds native to North America. In fact, in parts of the southern U.S. from the Gulf Coast to the Atlantic, tropical milkweed can produce foliage and flowers year-round. This allows monarchs in those areas to stay put and keep breeding all winter.

And that's how problems with disease arise.

Satterfield and her colleagues processed more than 5,000 samples taken from monarchs at over 100 sites across the U.S., Canada and Mexico, testing them for infection by a debilitating protozoan parasite. The non-destructive samples, about half of which were collected by citizen scientists through Project Monarch Health, were taken by gently pressing clear tape against the butterfly's abdomen; the samples were then viewed under a microscope.

The researchers found that the non-migratory, winter-breeding monarchs in the southern U.S. were five times more likely to be infected with parasites than migratory monarchs sampled in their summer breeding range or at overwintering sites in Mexico.

Satterfield said that previous studies by co-author Sonia Altizer, Odum School associate dean and UGA Athletic Association Professor in Ecology, showed that for some wildlife species, including monarchs, long distance migration helps to reduce infectious disease transmission.

"Long distance migration can reduce disease in animal populations when it weeds out infected individuals during the strenuous journey, or when the migrating animals get to take a break and move away from contaminated habitats where parasites accumulate," she said. "Our non-migratory monarchs don't have those benefits of migration, so we see that in many cases the majority of monarchs at winter breeding sites are infected."

Satterfield said that this pattern is part of a larger problem.

"Many animal migrations are changing in response to human activities, whether climate change, habitat destruction or barriers to migration," she said. "Some migrations are changing in terms of timing or distance traveled. Some animals have stopped migrating altogether. So in these animals, some pathogens that have been historically kept in check by migration might now become a problem."

Fortunately for the monarchs, there is a large and dedicated core of gardeners and citizen scientists eager to help.

"It was members of the public and citizen scientists who alerted us to the winter breeding behaviors of monarchs in their gardens to begin with," Satterfield said. "So the public has helped us recognize the shift in monarch ecology and document the disease outcomes in a scientific way. And I think they can now help us manage monarch habitats in ways that might reduce disease problems."

Because the monarchs' winter-breeding behavior is made possible by the presence of tropical milkweed, Satterfield recommended that gardeners gradually replace it with native milkweeds as they become available.

"We encourage the planting of native milkweeds whenever possible," she said. "But if you do have tropical milkweed, we recommend cutting it back every few weeks to within 6 inches of the ground in fall and winter. That's especially important in coastal areas of the southern U.S. where we now know disease is a problem." Some locations such as the extreme southern portions of Texas and Florida have supported tropical milkweed for many decades or longer, and Satterfield said that tropical milkweed there can be left in place.

Satterfield's recommendations are based in part on ongoing research by Altizer and Ania Majewska, an Odum doctoral student and Wormsloe Fellow at the UGA Center for Research and Education at Wormsloe in Savannah, where they are testing butterflies' responses to native and non-native host plants in a series of experimental pollinator gardens.

Satterfield said that while the chief driver of the monarch's decline is the loss of native milkweeds in the U.S. and Canada, it's important to tackle the issue of pathogen transmission in winter-breeding populations. "Things could get worse for the monarchs if we don't solve this problem now with the tropical milkweed supporting high levels of disease," she said.

###

More information about monarchs, parasites and milkweed is available online at http://www.monarchparasites.org and monarchjointventure.org/images/uploads/documents/Oe_fact_sheet.pdf. A list of native milkweeds by region is available at monarchjointventure.org/images/uploads/documents/MilkweedFactSheetFINAL.pdf.

The study's third co-author was John Maerz of the UGA Warnell School of Forestry and Natural Resources. The research, available online at http://rspb.royalsocietypublishing.org/content/282/1801/20141734.full, was supported by the National Science Foundation and the U.S. Forest Service.

Media Contact

Dara Satterfield
dara7@uga.edu
706-542-3485

 @universityofga

http://www.uga.edu

Dara Satterfield | EurekAlert!

Further reports about: UGA animals breeding citizen scientists migrating monarch butterflies native parasites tropical

More articles from Life Sciences:

nachricht Closing the carbon loop
08.12.2016 | University of Pittsburgh

nachricht Newly discovered bacteria-binding protein in the intestine
08.12.2016 | University of Gothenburg

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Significantly more productivity in USP lasers

In recent years, lasers with ultrashort pulses (USP) down to the femtosecond range have become established on an industrial scale. They could advance some applications with the much-lauded “cold ablation” – if that meant they would then achieve more throughput. A new generation of process engineering that will address this issue in particular will be discussed at the “4th UKP Workshop – Ultrafast Laser Technology” in April 2017.

Even back in the 1990s, scientists were comparing materials processing with nanosecond, picosecond and femtosesecond pulses. The result was surprising:...

Im Focus: Shape matters when light meets atom

Mapping the interaction of a single atom with a single photon may inform design of quantum devices

Have you ever wondered how you see the world? Vision is about photons of light, which are packets of energy, interacting with the atoms or molecules in what...

Im Focus: Novel silicon etching technique crafts 3-D gradient refractive index micro-optics

A multi-institutional research collaboration has created a novel approach for fabricating three-dimensional micro-optics through the shape-defined formation of porous silicon (PSi), with broad impacts in integrated optoelectronics, imaging, and photovoltaics.

Working with colleagues at Stanford and The Dow Chemical Company, researchers at the University of Illinois at Urbana-Champaign fabricated 3-D birefringent...

Im Focus: Quantum Particles Form Droplets

In experiments with magnetic atoms conducted at extremely low temperatures, scientists have demonstrated a unique phase of matter: The atoms form a new type of quantum liquid or quantum droplet state. These so called quantum droplets may preserve their form in absence of external confinement because of quantum effects. The joint team of experimental physicists from Innsbruck and theoretical physicists from Hannover report on their findings in the journal Physical Review X.

“Our Quantum droplets are in the gas phase but they still drop like a rock,” explains experimental physicist Francesca Ferlaino when talking about the...

Im Focus: MADMAX: Max Planck Institute for Physics takes up axion research

The Max Planck Institute for Physics (MPP) is opening up a new research field. A workshop from November 21 - 22, 2016 will mark the start of activities for an innovative axion experiment. Axions are still only purely hypothetical particles. Their detection could solve two fundamental problems in particle physics: What dark matter consists of and why it has not yet been possible to directly observe a CP violation for the strong interaction.

The “MADMAX” project is the MPP’s commitment to axion research. Axions are so far only a theoretical prediction and are difficult to detect: on the one hand,...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

ICTM Conference 2017: Production technology for turbomachine manufacturing of the future

16.11.2016 | Event News

Innovation Day Laser Technology – Laser Additive Manufacturing

01.11.2016 | Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

 
Latest News

Closing the carbon loop

08.12.2016 | Life Sciences

Applicability of dynamic facilitation theory to binary hard disk systems

08.12.2016 | Physics and Astronomy

Scientists track chemical and structural evolution of catalytic nanoparticles in 3-D

08.12.2016 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>