Scientists unravel the molecular basis of monarch butterfly migration

Since its discovery, the annual migration of eastern North American monarch butterfly has captivated the human imagination and spirit. That millions of butterflies annually fly up to 2000 miles to reach a cluster of pine groves in central Mexico comprising just 70 square miles is for many an awesome and mysterious occurrence. However, over the past decade, scientists have begun to unveil the journey for what it is—a spectacular result of biology, driven by an intricate molecular mechanism in a tiny cluster of cells in the butterfly brain.

University of Massachusetts Medical School Professor and Chair of Neurobiology Steven M. Reppert, MD, has been a pioneering force in the effort to demystify the migration of the monarch. His previous research has demonstrated that the butterflies use a time-compensated sun compass and daylight cues to help them navigate to the pine groves. His studies have shown that time compensation is provided by the butterfly’s circadian clock, which allows the monarch to continually correct its flight direction to maintain a fixed flight bearing even as the sun moves across the sky.

Now, in two papers published in January 8 journals of the Public Library of Science (PLoS), Dr. Reppert and colleagues describe a novel circadian clock mechanism in monarch butterflies that is important for accurate navigation, and reveal for the first time a genomic resource for identifying the genes involved in monarch migration.

In “Cryptochromes Define a Novel Circadian Clock Mechanism in Monarch Butterflies That May Underlie Sun Compass Navigation, ” published in PLoS Biology, Reppert and colleagues reveal that the circadian clock of the monarch uses a novel molecular mechanism, heretofore not found in any other insect or mammal.

By studying the clock in two other organisms—the fruit fly (Drosophila) and the mouse—scientists thought that they had very good models for an understanding of the insect clock and the mammalian clock, respectively. Through these studies, scientists had described a clock mechanism that is essentially a loop where proteins are made and destroyed over a cycle that takes approximately 24 hours to complete. Further, investigators identified those factors that work together to drive this process.

Reppert and colleagues were particularly interested in one of these factors— cryptochrome (CRY), a protein that was initially discovered in plants and was subsequently found in the fly and the mouse. In the fly, CRY functions as a blue light photoreceptor, allowing light access to clock-containing cells. This enables the resetting of the clock by the light-dark cycle. In the mouse, CRY does not function to absorb light; rather it is one of the essential components that power the central clockwork enabling the feedback loop to continue. (In the mouse, light enters the clock through the animal’s eyes.)

Given the function of CRY in flies and the role of light in migration, scientists presumed that the monarch’s clock would resemble that of the fly. Reppert and his collaborators were stunned and elated to find that the clock of the butterfly was as spectacular as its migration. Genetic studies revealed that the monarch had not only the fly-like CRY, but also another cryptochrome that further tests identified as a new clock molecule in the butterfly. Surprisingly, this cryptochrome, dubbed CRY2, is more similar in structure to vertebrate CRY than to that of the fruit fly.

Notably, the scientists also found that the core components of the monarch clock resembled those of the mammalian clock. As in the mouse, CRY2 functions in the butterfly to maintain the feedback loop, while CRY1 still allows light to access the cells, as in the fly.

“This is a very interesting realignment of how one thinks about how insect clocks work. There was no reason to suspect that the butterfly clock would be different from that of Drosophila. That it is different has already told us something about how circadian clocks have evolved,” explained Reppert. “What we have in the butterfly is an astounding clock mechanism, one that is more similar to our own circadian clock and less similar to the clock of the fly! The presence and function of two distinct CRYs suggest that the monarch’s is an ancestral clock; a clock that, over the course of evolution, has changed differently in other insects and mammals.”

Reppert and co-workers not only discovered the function of CRY2 in the monarch clock, but they also found that CRY2 may function to mark a critical neural pathway from the circadian clock to the sun compass. This clock-to-compass pathway provides an essential link between the clock and the sun compass, as both are necessary for successful orientation and navigation during migration. As Reppert explains, “CRY2 appears to have a dual function— as a core clock component and as an output molecule, linking the clock to the compass.”

Concurrent with their studies of the monarch clock and relevant to the identification of CRY2, Reppert and colleagues have been working to create a butterfly genomics resource.

In “Chasing Migration Genes: A Brain Expressed Sequence Tag Resource for Summer and Migratory Monarch Butterflies (Danaus plexippus),” published in PLoS One, Reppert and his collaborators describe a brain expressed sequence tag (EST) resource, used to identify genes involved in migratory behaviors by comparing the gene expression in the brains of migrating butterflies to those of non-migrating butterflies. They have already identified ~10,000 ESTs that likely represent over 50 percent of the genes that make up the monarch genome. The ESTs, which represent expression units of genes in the butterfly brain, are currently being analyzed and catalogued and Reppert hopes that the genetic information will be of wide use to scientists around the world.

“This information, along with genetic markers identified in the study, will help us distinguish genetic differences between populations or even between migrating and non-migrating subspecies of monarchs” Reppert said, adding, “This information sets the stage for the cloning of the butterfly genome.”

In fact, Reppert and his fellow investigators recently initiated a collaborative agreement with SymBio Corporation (www.sym-bio.com) of Menlo Park, Calif., to sequence the entire butterfly genome. According to Robert A. Feldman, President and CEO of SymBio, “We are very excited about the prospect of sequencing the monarch genome. The information gained will not only help elucidate the molecular basis of butterfly migration, but will also add substantial knowledge to comparative genomic studies.” SymBio specializes in sequencing the genomes of a wide range of organisms, from bacteria to mammals.

Ultimately, the Reppert laboratory will continue to work to understand how the monarch clock “talks” to the sun compass, with a focus on CRY2. The goal of the researchers’ studies is to understand the molecular mechanism and anatomical mechanisms for clock-compass interactions that enable migrants to maintain a set flight bearing as the sun moves across the sky during the day.

“The monarch provides a fascinating animal model for the study of neural processes. By understanding more about the way the circadian clock and the sun compass interact to allow the monarch to fulfill its biological destiny, we will gain valuable insights into how the brain functions to incorporate information about time and space, which has relevance far beyond the butterfly,” said Reppert.

Source UMASS Medical School press release

Vermont County Bird Quest 2011

Ready for a birding challenge and some 'friendly' cross-county competition? Grab your binocs, shoulder your spotting scope, and join the 2011 Vermont County Birding Quest. Many counties have challenged one another to identify as many species as possible during 2011.

Part fun, part discovery, part conservation, but mostly fun, this yearlong quest gives us all a welcome excuse to head outdoors and go birding. From the common to the rare, a diverse and fascinating array of birds resides in or passes through Vermont each year. Each county now seeks to document that diversity, with the added incentive of vying for top honors of the maximum species count. Vermont eBird will provide the tool for that documentation.

Expanding from the Norwich 2010 Birding Quest, which tallied 168 species within the town borders during the past year, now nearly all the counties are embarking on a friendly rivalry for 2011. We expect a great deal of cross-county collaboration, some good-natured taunting, and plenty of avian surprises.

The main idea behind the Quest is to get people out birding, promote camaraderie, and better document Vermont's bird life. We encourage each county that participates to organize periodic outings for the birding-interested public.

The bell has rung, the gloves are down, let the competition begin! Get out there, find some birds, and enter them all on Vermont eBird.

Researchers show environmental changes may affect vital cooperate bird behaviors

While scientists believe that climate change and related extreme weather events such as drought and flooding will likely affect the earth's flora and fauna, just how much is not known. A new study by researchers Walter Jetz from Yale University and Dustin Rubenstein from Columbia University however shows an important link between the natural variation in climate conditions and complex behaviors among birds.

The study, which appears in print in Current Biology on Jan. 11, 2011, has implications for understanding how organisms may respond behaviorally to increased climate variability resulting from climate change. They argue that species that live in families may be better guarded against the effects of unpredictable climatic conditions.

Family-living, or cooperative breeding, is common among birds. Cooperative breeding societies, such as humans, are typically characterized by groups of relatives that work together to raise young. Usually, some birds forgo their own reproduction to help raise others' offspring. However, some cooperative breeding societies consist of groups of non-relatives that also work together in raising young. From Australia to the Amazon, cooperatively breeding birds account for approximately 831 species—or nearly 10 percent—of the nearly 10,000 avian species worldwide.

Using a behavioral data set of more than 95 percent of the world's birds, and a global 40-year climate dataset, the researchers examined how environmental factors—like mean and variation in temperature and rainfall—and biotic factors—like body mass, diet breadth and type—influence the incidence and global distribution of family-living in birds.

"Scientists have long known that family-living birds are more common in some parts of the world than others," said Rubenstein, assistant professor of ecology, evolution & environmental biology. "But this is the first time that we have been able to study the geographic distribution of complex avian social behavior on a global scale, while simultaneously examining how the environment influences these geographic patterns."

By combining behavioral and climate data in a statistical modeling framework the researchers found dramatic spatial and environmental variation in social behavior globally. "We discovered 'hot-spots' in places like Australia and Africa where family-living species are overrepresented, as well as 'cold-spots' in places like South and Central America where there are fewer family-living species than we would have expected," said Jetz. This geographic unevenness coincided with the occurrence of specific bird lineages, but also carried a strong signal of environmental and biotic factors. In particular, among year variation, or climatic uncertainty, in rainfall emerged as a key predictor of family-living in birds.

The study demonstrates that even on a global scale, the incidence of complex avian social behavior may be greatly influenced by the consequences of living in unpredictable environments. Variable environments encompass a broad range of climate conditions that pose a greater range of challenges to survival and reproduction than predictable ones. Family-living among birds may therefore be a conservative "'best of a bad job'' strategy to maximize fitness when breeding conditions vary unpredictably from year to year.

"Families act as insurance against environmental uncertainty," said Rubenstein. "Just as predicting a drop in the stock market is difficult, so too is determining when food is going to be scarce." When times are bad and food is difficult to find, joining up to raise young may pay off for both parents and helpers.

This thinking may have implications for an entirely different group of animals: humans. "Think twice," cautions Rubenstein, "before you kick your grown kids out of the house, as you never know when you might need them."

Source: Columbia University press release.

Natural dissolved organic matter plays dual role in cycling of mercury

Nature has a bit of a Jekyll and Hyde relationship with mercury, but researchers at the Department of Energy's Oak Ridge National Laboratory have made a discovery that ultimately could help explain the split personality.

While scientists have known that microbes in aquatic environments make methylmercury, a more toxic form of mercury that accumulates in fish, they also know that nature and other types of bacteria can transform methylmercury to less toxic forms. What they haven't completely understood are the mechanisms that cause these transformations in anoxic environments – lacking in oxygen – in nature.

"Until now, reactions between elemental mercury and dissolved organic matter have rarely been studied in anoxic environments," said Baohua Gu of the the lab's Environmental Sciences Division.

In a paper published in the Proceedings of the National Academy of Sciences, a team led by Gu reports that compounds from the decay of organic matter in aquatic settings affect mercury cycling. Low concentrations of these compounds can chemically reduce mercury, but as those concentrations increase, that reaction is greatly inhibited. They performed their experiments by simulating conditions found in nature.

"This study demonstrates that in anoxic sediments and water, organic matter is not only capable of reducing mercury, but also binding to mercury," said co-author Liyuan Liang. "This binding could make mercury less available to microorganisms for making methylmercury."

The authors also noted that their paper offers a mechanism that helps explain the seemingly contradictory reports on the interaction of organic matter and mercury in nature.

Gu and Liang hope this newly gained knowledge will play a role in helping to understand how mercury cycles in aquatic and sediment environments and help in informed decision-making for mercury-impacted sites around the nation.

"Our long-term goal is to understand the mechanisms controlling the production of methylmercury in the environment, " Liang said. "This understanding could lead to ways to reduce levels of mercury in fish as this is a global problem of enormous significance."

Mercury is distributed around the globe mainly through the burning of coal, industrial uses and through natural processes such as volcano eruptions. Various forms of mercury are widely found in sediments and water.

This research benefits from ORNL's expertise in field-to-laboratory geochemistry and microbiology, computational modeling and simulation, world-class neutron sources and high-performance computing.

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Other authors of the paper, "Mercury reduction and complexation by natural organic matter in anoxic environments," are Carrie Miller and Wenming Dong of ORNL and Yongrong Bian and Xin Jiang, visiting scientists from the Chinese Academy of Science.

You can read about VCE's mercury studies at http://www.vtecostudies.org/BITH/mercury.html

Recent Bird Kills Only Tip of the Iceberg

Recent reports of thousands of dead birds falling from the sky in Arkansas, while getting much attention in the press, only represent a tiny fraction of birds killed each year due to human causes, according to American Bird Conservancy, the nation’s leading bird conservation organization.

“There are many human-related causes of bird mortality including buildings, outdoor cats, pesticides, communication towers, automobiles, wind farms, and lead poisoning from spent ammunition and lost fishing tackle. But because most of the deaths from those sources often occur in ones or twos, they often go unnoticed or unreported,” said ABC Vice President Mike Parr.

According to Parr, estimates from various studies show that up to one billion birds may be killed each year in collisions with buildings; another half a billion may die due to predation by outdoor cats; up to 50 million may die in collisions with communication towers; perhaps 15 million die annually due to pesticide poisoning and there is growing concern about bird mortality caused by the burgeoning wind industry.

“When you look at the totality of human-caused threats to birds, it has got to give cause for serious concern about our cumulative effects on their populations,” Parr said.

Several threats have been dramatically reduced, but much still needs to be done. For example, thanks to advocacy efforts by ABC and other members of the National Pesticide Reform Coalition, the cancellation or restriction of some of the most toxic pesticides to birds, such as carbofuran, fenthion and ethyl parathion, has reduced bird mortality by as much as 75%, yet millions still die as a result of pesticide poisoning each year.

Collisions with buildings could be drastically reduced if technology continues to advance in the development of bird-friendly or bird-safe glass for buildings. Several products have already been developed to reduce the incidence of bird impacts, but architects and city planners still need a greater understanding of the problem and the importance of making buildings bird safe.

“Bird-safe building glass is no longer a pie-in-the-sky dream. Its reality is on the horizon – we are close. The manufacturers are working with the scientists; they’re working with us. And local communities are getting into the act as well, with more and more cities – such as San Francisco – looking at policies that implement bird-friendly construction,” Parr added.

Last Spring, an agreement was reached between ABC and its partners and the telecommunications industry, that would dramatically reduce the number of birds killed at communication towers. If that agreement is accepted by the Federal Communications Commission, new tall towers that pose the highest threat to birds would be subject to a greater level of environmental review – including independent assessment. A preferred standard of lighting styles would also be implemented. Groundbreaking as this agreement is, it does not address the thousands of towers already permitted and built across the American landscape that continue to kill birds.

Efforts continue to reduce the number of birds killed by wind turbines. A key action that will likely be decided in the next few months will involve a decision by the Department of the Interior to implement wind turbine siting and operational guidelines. ABC believes these guidelines should be made mandatory .

“Voluntary guidelines don’t work. We wouldn’t expect people to pay voluntary taxes. We can’t expect the wind industry to follow voluntary environmental guidelines either,” Parr said.

Wind farms such as the one shown above at Altamont Pass in California are already killing hundreds of thousands of birds each year. Photo: Mike Parr. High resolution photo available on request.

Vermont County Birding Quest Takes Flight

Ready for a birding challenge and some 'friendly' cross-county competition? Grab your binocs, shoulder your spotting scope, and join the 2011 Vermont County Birding Quest. The adjoining counties of Windsor, Washington, and Orange have challenged one another to identify as many species as possible during 2011.

Part fun, part discovery, part conservation, but mostly fun, this yearlong quest gives us all a welcome excuse to head outdoors and go birding. From the common to the rare, a diverse and fascinating array of birds resides in or passes through Vermont each year. These three counties now seek to document that diversity, with the added incentive of vying for top honors of the maximum species count. Vermont eBird will provide the tool for that documentation.

Expanding from the Norwich 2010 Birding Quest, which tallied 168 species within the town borders during the past year, Windsor, Washington and Orange Counties are embarking on a friendly rivalry for 2011. We expect a great deal of cross-county collaboration, some good-natured taunting, and plenty of avian surprises. Washington surged to an early lead in eliciting birder envy among its county rivals, with the late December discovery in Berlin of a Northern Hawk Owl, which lingered through January 2. Windsor and Orange County birders are, of course, hoping the bird flew south and east and will reappear in our neck of the woods!

VCE and North Branch Nature Center are co-sponsoring the County Quest challenge, and there will be prizes awarded in several categories. Stay tuned for further details and updates as we all sharpen our birding skills and share our finds in the months ahead. We hope that the Vermont County Quest will expand statewide in 2012. In the meantime, we encourage any and all birders from both inside and outside Vermont to join us in the 2011 Quest!


Photo of Northern Hawk Owl courtesy of Bryan Pfeiffer, Wings Photography

VCE Research Associate Jason Townsend Awarded AFO Best Presentation 2010

Jason Townsend, a Ph.D. candidate at SUNY College of Environmental Science and Forestry in Syracuse New York and VCE research associate, was awarded Best Presentation by Association of Field Ornithologists at their annual meeting. His presentation was titled, Catharus thrushes as bioindicators of mercury hotpots: from the Catskills to the Caribbean. VCE co-authors on the presentation were Chris Rimmer and Kent McFarland and Charles T. Driscoll from Syracuse University, Center for Environmental Systems Engineering.

Jason’s research documented mercury bioaccumulation in a densely forested watershed of the Catskill Mountains, NY. Mercury is a potent neurotoxin that accumulates in the environment as a result of global atmospheric pollution. While many studies have documented mercury accumulation in aquatic ecosystems, little is known about mercury cycling in strictly terrestrial ecosystems. Jason’s study showed that mercury accumulation in the soil and leaf litter increased with elevation in this watershed. Thrushes of the genus Catharus, which are arrayed along this elevational gradient, also showed increased blood mercury content with increasing elevation. High elevation Bicknell’s Thrushes (C. bick- nelli) and Swainson’s Thrushes (C. ustulatus) showed significantly greater blood mercury levels than did lower elevation congeners, Hermit Thrush (C. guttatus) and Veery (C. fuscescens). This finding could have particularly important health and conservation implications for Bicknell’s Thrush, which is generally restricted to forests above 1000 m in the northeastern United States. Furthermore, blood mercury levels in all species declined with season, indicating that early-season thrushes either carry mercury from their winter grounds or consume a diet higher in mercury during the early part of the breeding season (May –June 15).

An additional analysis of mercury in Bicknell’s Thrushes wintering on Hispaniola showed the highest blood mercury levels of any birds in this study and also wide, site-specific variance, potentially reflecting local pollution patterns.

Patterns of widespread decline in North American bumble bees

Bumble bees (Bombus) are vitally important pollinators of wild plants and agricultural crops worldwide. Fragmentary observations, however, have suggested population declines in several North American species. Despite rising concern over these observations in the United States, highlighted in a recent National Academy of Sciences report, a national assessment of the geographic scope and possible causal factors of bumble bee decline is lacking. Here, we report results of a 3-y interdisciplinary study of changing distributions, population genetic structure, and levels of pathogen infection in bumble bee populations across the United States. We compare current and historical distributions of eight species, compiling a database of >73,000 museum records for comparison with data from intensive nationwide surveys of >16,000 specimens. We show that the relative abundances of four species have declined by up to 96% and that their surveyed geographic ranges have contracted by 23–87%, some within the last 20 y. We also show that declining populations have significantly higher infection levels of the microsporidian pathogen Nosema bombi and lower genetic diversity compared with co-occurring populations of the stable (nondeclining) species. Higher pathogen prevalence and reduced genetic diversity are, thus, realistic predictors of these alarming patterns of decline in North America, although cause and effect remain uncertain.

Source: Abstract from paper published in PNAS

Photo: Bumblebee landing on a turtlehead flower in Vermont. By K.P. McFarland

News Article: http://news.nationalgeographic.com/news/2011/01/110104-bumblebees-bees-decline-fungus-mystery-science-animals/

Norwich 2010 Birding Quest Tops its Goal

The annual Christmas Bird Count (CBC) punctuated both ends of the Norwich 2010 Birding Quest, which exceeded all expectations by tallying 168 species. On January 1 a year ago, the Hanover-Norwich CBC ushered in a strong start for the Quest and included a ' southerner', Carolina Wren. A year later, last weekend's CBC on December 31 produced a number of noteworthy finds inside the Norwich town lines, although none were new for the year. Belted Kingfisher and Swamp Sparrow were surprises, as was a Barred Owl mantling a freshly-killed American Crow!

As expected once fall migration subsided, November and December brought a major slowdown in additions of species to the Norwich Quest master list, with only 5 newcomers. However, all were welcome finds and included, in chronological order:

164 Black Scoter -- Ompompanoosuc River mouth, 5 November
165 Eurasian Collared-Dove -- Union Village Road, 6 November
166 Tundra Swan -- Ompompanoosuc River mouth, 20 November (a one-day wonder)
167 Red-bellied Woodpecker -- Kendall Station Road, 16 December
168 Common Redpoll -- Route 5 south, 17 December

The Eurasian Collared-Dove was especially intriguing, in that it appeared at the same Union Village Road feeder as did a bird (Vermont's first-ever record) in November of 2009. It is tempting to suspect that this wayward individual, which lingered only 2 days, was the same bird that appeared a year earlier, though its whereabouts and activities in the intervening year would be anyone's guess.

The final Norwich 2010 Quest species, Common Redpoll, is now fairly common throughout the Upper Valley, as it has staged a moderate invasion from its subarctic Canada range. Few other boreal finches are currently about, but we're all hoping Pine Grosbeaks and crossbills will show up soon. Birders should watch for mixed flocks of Cedar and Bohemian Waxwings on ornamental fruit trees.

Our final tally of 168 species easily eclipsed our original goal of 150. Avian highlights within Norwich during 2010 included Northern Shoveler, Long-tailed Duck, Northern Harrier, Short-billed Dowitcher, Olive-sided Flycatcher, Philadelphia Vireo, Bicknell's Thrush, Bay-breasted Warbler, Rusty Blackbird, and Orchard Oriole. With Vermont eBird enabling us to systematically track species, a remarkable total of 773 eBird checklists were submitted! This more than admirably fulfilled one of the Quest's goals of encouraging greater use of this invaluable birding and conservation tool.

We were also pleased to offer monthly birding excursions to the public, beginning and ending with the two CBCs. Nearly 200 people participated in these outings, which ranged from leisurely walks around the village, to a bird banding demonstration at the Milton Frye Nature Area, to trips along the Connecticut River. Participants included youth and senior citizens, and all were enthusiastic to learn more about Norwich's birdlife and explore its special places.

Plans for 2011 involve an expansion to all of Windsor County, with a special "challenge" in the form of a friendly rivalry with our birding colleagues in neighboring Washington and Orange Counties. Stay tuned for details on this yearlong effort, which promises to be fun, entertaining, and full of surprises. We think 200 species is entirely within reach in Windsor County, and we're off to a good start already!

Thanks to everyone who participated in the Norwich 2010 Birding Quest. We'll again keep careful track of all species encountered within the town lines during 2011, even as we set our sights on the entire county.

Chris Rimmer
Doug Hardy
Spencer Hardy
George Clark

Common Redpoll photo courtesy of Steve Faccio