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Saturday, August 20, 2022

MSU is forecasting the future to help protect monarch butterflies 

MICHIGAN STATE UNIVERSITY

EAST LANSING, Mich. – The outlook for monarch butterflies isn’t great right now. In fact, the International Union for the Conservation of Nature, or IUCN, just added North America’s monarchs to its list of endangered species.

With news like this, it can be easy to overlook the reasons to be hopeful that we can protect these iconic insects from extinction. But those bright spots are there if people know where to look.

Now, there are forecasts to help guide conservation, thanks to Michigan State University’s Elise Zipkin and her colleagues.

Working with extensive data sets and established models, the team has forecasted which counties in the midwestern U.S. and Ontario, Canada, are most likely to offer the most hospitable breeding grounds for monarchs in the face of climate change. These forecasts, published Aug. 19 in the journal Global Change Biology, can help identify where the greatest opportunities to support monarch conservation may be.

“These projections let us look at how monarch populations will change across the Midwest and say, ‘Here’s where they’ll likely do a little better, here’s where they might do a little worse,’” said Erin Zylstra, the first author of the new report and a former postdoctoral researcher in the Zipkin Quantitative Ecology Lab.

The Midwest is an important summer breeding area for eastern monarch butterflies. Over the course of a year — and four generations — monarchs migrate between central Mexico and parts of the U.S. and southern Canada east of the Rocky Mountains.

But between 1996 and 2014, the eastern monarch population has decreased by more than 80%. Last year, Zylstra, Zipkin and their colleagues published a paper showing that climate conditions were the major driver of recent declines.

Building on that 2021 study, the team took its understanding of how climate influenced monarch populations since 2004 and used that to forecast what could happen over the next 80 years under a range of climate change scenarios.

Researchers have projected that climate change will continue driving monarch populations down. However, the areas that are least affected in the Midwest, such as northern Ohio and southern Michigan, can become targets to slow or reverse that trend.

CREDIT

Credit: Global Change Biology

“Climate change is a huge global problem that requires nations working together to solve. When we talk about conservation, though, we tend to want to know what we can do in our local communities,” said Zylstra, who is now a quantitative ecologist with the Tucson Audubon Society in Arizona. “If we can find the places where the impacts of climate change aren’t expected to be so bad, those could become the areas where we invest our resources.”

“In general, our research is informed by asking what are the conservation needs,” said Zipkin, the senior author of the study and an associate professor in the College of Natural Science’s Department of Integrative Biology. She’s also the director of the Ecology, Evolution and Behavior Program, a pillar of MSU’s overall ecology program, which was recently ranked No. 32 globally.

Zipkin and Zylstra’s latest work was supported by the National Science Foundation and U.S. Geological Survey’s Midwest Climate Adaptation Science Center, which facilitates partnerships between scientists, community leaders and natural resource managers.

“We’re answering scientific questions that we think are important, but we are also working with on-the-ground individuals and agencies that can use our work to implement strategic conservation,” Zipkin said. “The Midwest Climate Adaptation Science Center helps us get our research directly into the hands of those people who are thinking about next steps.”

Another unique feature of the work is how it considers sources of uncertainty and provides quantitative estimates for those, the researchers said. This approach — which explicitly considers what is unknown about the future — can help the research community better understand and utilize the team’s results and models. It also helps researchers identify what’s needed to improve the precision of future forecasts.

For example, unknowns about future climate are the largest source of uncertainty as the team forecasts what monarch populations will look like at the end of the 21st century. But in the immediate future, uncertainties about exactly how specific climate variables influence local monarch population abundances loom large. Collecting more robust, targeted monarch data could thus improve projections in the short term.

In the meantime, Zylstra and Zipkin have presented their best and most data-informed forecasts in collaboration with Naresh Neupane, a climate scientist at Georgetown University. The team forecasted monarch population changes in counties throughout the summer breeding grounds and on the overwintering grounds in Mexico under four different climate scenarios.

In each scenario, the forecasts suggest that the eastern monarch population will continue to decline, which is not surprising given the butterflies’ current trajectory. But identifying the pockets where, locally, populations are growing or holding constant provides hope that the decline can be slowed or reversed.

And if the approach helps save monarchs, it can help with other threatened species, too.

“Monarchs are special. They’re beautiful, easy to identify, widely distributed and they get people to care about conservation in general,” Zipkin said. “Absolutely, with action, we can protect our planet, we can protect other migratory species, we can protect pollinators and we can protect monarchs.”  

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Michigan State University has been advancing the common good with uncommon will for more than 165 years. One of the world's leading research universities, MSU pushes the boundaries of discovery to make a better, safer, healthier world for all while providing life-changing opportunities to a diverse and inclusive academic community through more than 200 programs of study in 17 degree-granting colleges.  

For MSU news on the Web, go to MSUToday. Follow MSU News on Twitter at twitter.com/MSUnews.

JOURNAL

Global Change Biology

DOI

10.1111/gcb.16349

Sweet sap, savory ants

Woodpeckers taste sweet, but wrynecks—unusual woodpeckers that specialize on ants—lost the ability to taste sugars

Peer-Reviewed Publication

MAX-PLANCK-GESELLSCHAFT

Great spotted woodpecker — IMAGE: GREAT SPOTTED WOODPECKER (DENDROCOPOS MAJOR). BY REPURPOSING THEIR SAVORY RECEPTORS, WOODPECKERS ARE ABLE TO DETECT SUGAR IN SAP, NECTAR OR FRUIT. view more
CREDIT: JAN ANDERSSON (MACAULAY LIBRARY ML211906341)

Many mammals have a sweet tooth, but birds lost their sweet receptor during evolution. Although hummingbirds and songbirds independently repurposed their savory receptor to sense sugars, how other birds taste sweet is unclear. Now, an international team lead by researchers from the Max Planck Institute for Biological Intelligence (in foundation) shows that woodpeckers also regained sweet taste. Interestingly, wrynecks, specialized ant-eating woodpeckers, selectively reversed this gain through a simple and unexpected change in the receptor. These results demonstrate a novel mechanism of sensory reversion and highlight how sensory systems adapt to the dietary needs of different species.

Birds, the descendants of carnivorous dinosaurs, lack part of the sweet receptor found in mammals. This should leave them insensitive to sugars. However, recent studies have shown that both hummingbirds and songbirds have regained the ability to sense sugar by repurposing their savory receptor to now detect carbohydrates in fruits and nectar. How other birds sense sugars, and the extent to which taste receptor responses track the immense dietary diversity of birds, is unclear. To investigate this question, Julia Cramer and Maude Baldwin from the Research Group Evolution of Sensory Systems and colleagues from other universities* focused on woodpeckers. Although primarily insectivorous, this group of birds also contains multiple species that include sugar-rich sap, nectar, and fruits in their diets.

Using behavioral tests of wild birds, Baldwin’s group showed that woodpeckers clearly prefer sugar and amino-acids over water. Surprisingly, wrynecks – a member of the woodpecker group whose diet is almost exclusively composed of ants – displayed preferences for amino acids but not sugars. “Our next question was whether the observed sugar preference is mirrored by the birds’ receptors,” recaps Baldwin.

Common ancestor possessed sugar receptor

Functional analyses of taste receptors confirmed that woodpecker receptors were sensitive to sugars, whereas those of wrynecks were not. Interestingly, ancestral reconstructions indicated that the common ancestor of wrynecks and woodpeckers already possessed a modified savory receptor capable of responding to sugars. “This finding unveiled a third case of independent sugar-sensing evolution via modification of the savory receptor in birds”, says Cramer, the study’s first author. “Yet, what was even more exciting was the implication that wrynecks subsequently lost the receptor’s new function.”

Cramer’s meticulous dissection of differences between wryneck and woodpecker receptors revealed unexpectedly that changes in only a single amino acid in the wryneck receptor selectively turned off sugar-sensing: the birds kept their ability to taste savory, which is likely important for insect-specialist birds that consume a protein-rich diet.

These results trace an evolutionary history in which an early gain of sugar sensing in woodpeckers —possibly arising in an earlier ancestor and therefore older than woodpeckers themselves — was followed by its reversion when the wryneck receptor was later altered. “We were very surprised to find that this reversion is caused by changes in only one single amino acid, acting as a molecular switch to selectively regulate sugar sensitivity in wrynecks,” explains Cramer. “Unexpectedly, the result of this small change is that wrynecks are now again unable to detect sugar in their food but have retained the receptor’s ability to gather information on specific amino acid content. This makes a lot of sense when most of your diet is made up of ants.”

Further investigation will be required to describe how specific changes in taste receptors, and in other physiological and sensory systems, are related to the rich dietary diversity across birds.

* This study was conducted as a collaboration of researchers from the Max Planck Institute of Ornithology, now Max Planck Institute for Biological Intelligence (in foundation), the Cornell Lab of Ornithology, the University of Vienna and the University of Veterinary Medicine, Vienna, the Meiji University, and the Swedish University of Agricultural Science.

CAPTION

Acorn woodpeckers (Melanerpes formicivorus) often visit hummingbird feeders to drink sugar solutions.