Trees in the rainforest experience elevated nighttime temperatures and new research shows that may mean increased growth as well. Photo courtesy of the Smithsonian Tropical Research Institute

As the world warms, certain parts warm faster than others and it’s there that researchers are finding climate change clues that may alter our understanding of plant growth in general.

While average global temperatures have been rising at roughly 0.2 degrees Celsius per decade since 1975, the tropics have been warming slightly faster, at a rate of 0.26 degrees per decade. And in tropical Panama at night, things are getting even hotter. Researchers Alexander Cheesman and Klaus Winter found an increase of 1.5 degrees in average nighttime temperature over the past four decades. Testing what that jump might mean for tropical plants, the pair took fig and balsa tree seedlings and measured their growth at a range of increasing nighttime temperatures. What they found runs counter to the conventional climate change wisdom: the plants put on more than twice as much weight as the seedlings kept at normal conditions.

Traditional thinking, says Cheesman, who recently completed his post-doc fellowship with the Smithsonian Tropical Research Institute, says that during the day, plants undergo photosynthesis, capturing carbon and at night, they undergo respiration, losing carbon. The difference between the two governs the growth of the plant. Warmer temperatures increase respiration and thus, reduce growth, according to the model. But Cheesman says his research seriously challenges that rather simplistic understanding of respiration.

“It’s not that it’s just carbon loss because in losing that carbon it’s also doing all these other things: it’s producing ATP (adenosine triphosphate), it’s producing metabolic precursors that can be then used in building new cells.” Building on research that supports the productive purposes of respiration, Cheesman and Winter were able to show that rising temperatures did not increase respiration and thus slow growth, as expected, but rather increased both.

Using controlled-environment chambers and open-top chambers, the pair tested the growth of two neotropical tree species. Seedlings were maintained under constant daytime temperatures, matching those of central Panama, and exposed to elevated nighttime temperatures ranging from22 degrees to 31 degrees Celsius, or 72 degrees to 88 degrees Fahrenheit.

The latter group saw growth rates more than twice that of the first group. Cheesman thinks it’s likely, however, that trees with accelerated growth would stop growing once they reached a certain size, meaning there would not necessarily be larger trees in the forest. “You have plants achieving the same overall growth but at a faster rate,” explains Cheesman, “so it could well be that the turnover of forests becomes faster. ”

“There’s been a lot of this work done in agricultural systems with perennial and annual crop plants and similar things have been shown there,” but he says, “with trees it’s just fundamentally harder to run an experiment for the whole generation, from the seedling up to producing seedlings itself.”

Nonetheless, Cheesman thinks there’s a strong possibility increased respiration might mean shorter generations, which would have a whole host of implications for the plants’ ecological systems.

The faster rate may also mean a weaker plant. Independent from this study, another researcher, Whitman Miller of the Smithsonian Environmental Research Center in Edgewater, Maryland, working with seagrass found ”that elevated CO2 resulted in faster growth (a good thing), but accompanying reductions in protective chemical compounds (a bad thing).”

Cheesman says the finding lines up with his own experience studying tropical species.

“We see something similar in seedlings,” he says. “Increased nighttime temperature can result in increased shoot height and an increase in the internode length between leaves and so that has implications for things like structural integrity and potentially water movement in mature trees.” Weaker structures may make plants more susceptible to parasites or fungus, something Miller also notes in his work.

Though he believes his paper does signal a need to rethink models of photosynthesis-driven growth, Cheesman acknowledges the study’s limitations and the many unknowns.

“There are very important caveats in so much as, increasing nighttime temperatures will result in very different precipitation patterns and water availability which may have very profound implications on tree growth itself,” he says, citing one such outstanding question. “You’ve got a direct influence of the temperature and then a lot of indirect influences on all sorts of other things.”

He hopes his future research can expand what he’s started with Winter. “I’m interested in how temperature interacts with other processes, so not just photosynthesis and respiration but things like meristematic activity, leaf development, all of these processes and how they all tie into together into an integrated response to temperature.”

In honor of Leap Day 2012, we’re featuring some of the leapingest creatures in the Smithsonian Institution: frogs from the Panama Amphibian Rescue and Conservation Project.

The project is a partnership of zoos, parks and organizations—including the Smithsonian Tropical Research Institute—to help preserve endangered frog species in Panama. Over the past few decades, a fungus known as Batrachochytrium dendrobatidis (or Bd) has swept through frog populations around the world, causing species in the United States, Australia, Costa Rica and Puerto Rico to go extinct. Eastern Panama is one of the few places left free of Bd, and in order to save the diverse pool of endemic frog species, the project will create protective breeding centers, as well as a new research center at the National Zoo to find a cure for the fungus.

To honor tree frogs, bush frogs, leaf frogs and frogs of all types on this Leap Day, our friends at the project pulled together a list of leaping frog facts:

Not all frogs can leap, or even hop. The desert rain frog (Breviceps macrops) has legs that are too short to hop. Instead, it walks.

Male frogs of the genus Pipa are known to defend their territory by jumping at and then wrestling other males.

The New Guinea bush frog (Asterophrys turpicola) takes jump attacks one step further: before it jumps at a strange frog, it inflates itself and shows off its blue tongue.

Stumpffia tridactyla are normally slow-moving critters, but when they’re startled they can abruptly jump up to 8 inches. That doesn’t sound very far, but these little guys are less than half an inch long!

Read more facts at the project’s website.

How much is the Hope Diamond worth? Ask Smithsonian.

Our inquisitive readers are rising to the challenge we gave them last month. The questions are pouring in and we’re ready for more. Do you have any questions for our curators? Submit your questions here.

How much is the Hope Diamond worth? — Marjorie Mathews, Silver Spring, Maryland

That’s the most popular question we get, but we don’t really satisfy people by giving them a number. There are a number of answers, but the best one is that we honestly don’t know. It’s a little bit like Liz Taylor’s jewels being sold in December—all kinds of people guessed at what they would sell for, but everybody I know was way off. Only when those pieces were opened up to bidding at a public auction could you find out what their values were. When they were sold, then at least for that day and that night you could say, well, they were worth that much. The Hope Diamond is kind of the same way, but more so. There’s simply nothing else like it. So how do you put a value on the history, on the fact it’s been here on display for over 50 years and a few hundred million people have seen it, and on that fact it’s a rare blue diamond on top of everything else? You don’t. – Jeffrey E. Post, mineralogist, National Museum of Natural History

What’s the worst impact of ocean acidification so far?- Nancy Schaefer, Virginia Beach, Virginia

The impacts of ocean acidification are really just starting to be felt, but two big reports that came out in 2011 show that it could have very serious effects on coral reefs. These studies did not measure the warming effect of carbon dioxide in the atmosphere, but rather its effect of making the ocean more acidic when it dissolves in the ocean. Places where large amounts of carbon dioxide seep into the water from the sea floor provide a natural experiment and show us how ocean waters might look, say, 50 or 100 years from now. Both studies showed branching, lacy, delicate coral forms are likely to disappear, and with them that kind of three-dimensional complexity so many species depend on. Also, other species that build a stony skeleton or shell, such as oysters or mussels, are likely to be affected. This happens because acidification makes carbonate ions, which these species need for their skeletons, less abundant.

Nancy Knowlton, marine biologist
National Museum of Natural History

Art and artifacts from ancient South Pacific and Pacific Northwest tribes have similarities in form and function. Is it possible that early Hawaiians caught part of the Kuroshio Current of the North Pacific Gyre to end up along the northwest coast of America from northern California to Alaska? — April Amy Croan, Maple Valley, Washington

Those similarities have given rise to various theories, including trans-Pacific navigation, independent drifts of floating artifacts, inadvertent crossings by ships that have lost their rudders or rigging, or whales harpooned in one area that died or were captured in a distant place. Some connections are well-known, like feather garment fragments found in an archaeological site in Southeast Alaska that appear to have been brought there by whaling ships that had stopped in the Hawaiian Islands, a regular route for 19th-century whalers. Before the period of European contact, the greatest similarities are with the southwest Pacific, not Hawaii. The Kushiro current would have facilitated Asian coastal contacts with northwestern North America, but would not have helped Hawaiians. The problem of identification is one of context, form and dating. Most of the reported similarities are either out of their original context (which can’t be reconstructed), or their form is not specific enough to relate to another area’s style, or the date of creation cannot be established. To date there is no acceptable proof for South Pacific-Northwest Coast historical connections that predates the European whaling era, except for links that follow the coastal region of the North Pacific into Alaska.

William Fitzhugh, archeologist
Natural History Museum

A recent study indicates that ancient peoples in Peru were eating popcorn. Photo courtesy of the Smithsonian Tropical Research Institute

Popcorn dates pretty far back—way earlier than Orville Redenbacher—according to a study published last week. The paper, which appeared in Proceedings of the National Academy of Sciences and was co-authored by Dolores Piperno, curator of New World archaeology at the Museum of Natural History, reveals that archaeologists have unearthed a number of corn samples from a pair of Peruvian excavation sites. Several of the specimens indicate that among many uses the ancient Peruvians found for the maize was one we still know well today: popcorn.

The samples include corncobs, husks and stalks, and date to 6,700 to 3,000 years ago, making the discovery the oldest corn sample ever found in South America, says Piperno. “Corn was first domesticated in Mexico nearly 9,000 years ago from a wild grass called teosinte,” she says. “Our results show that only a few thousand years later corn arrived in South America, where its evolution into different varieties that are now common in the Andean region began.”

The excavation sites, Paredones and Huaca Prieta, are located in a climate that allows such samples to be preserved for a long time. “The sites occur in a very, very arid climate, the coast of Peru, where it almost never rains,” Piperno says. “Those kinds of conditions are particularly good for preserving things, because it’s humidity that affects the preservation of plant remains over time.”

Some of the ancient corn cobs discovered in Peru. Photo courtesy of the Natural History Museum

Although there had been previous discoveries of microfossils—such as starch grains—finding entire cobs provides valuable information. “Microfossils give an excellent picture of if they’re eating corn, if corn is present, but what was missing was the morphological detail,” says Piperno. “This site provided actual cobs, information on the sizes of the cobs, and what they look like.” These findings will help researchers trace the early domestication of corn from teosinte, a complicated transformation that occurred thousands of years ago.

The samples indicate that the inhabitants of the site consumed the maize in several different ways—apart from popcorn, they consumed corn flour—but that it was still not a common food at the time. “It was probably a fairly minor component of the diet, because despite the very good preservation, not many cobs were found,” Piperno says.

How did the corn travel all the way from Mexico, its birthplace, to Peru, thousands of miles away? “People just passed it along,” says Piperno. “Farmers like to exchange goods and ideas, so it was probably just passed from person to person, from farmer to farmer.”

Got a burning question about popcorn or some other zany topic? We invite you to submit questions to our new reader forum, Ask Smithsonian. Each month, we’ll select a handful of reader-submitted questions to publish in Smithsonian magazine with answers from the Institution’s experts.

Laetitia Plaisance searches for crustaceans in a piece of dead coral. Photo courtesy of Laetitia Plaisance.

Despite having offices just across the National Mall from each other, it was in the tiny town of Bocas del Toro, Panama, that I met Laetitia Plaisance. It was September 2009, and I was at the Smithsonian Tropical Research Institute’s field station in Bocas tagging along with coral reef biologist Nancy Knowlton, as she studied a coral reef’s mass spawning event. Plaisance, a marine ecologist at the National Museum of Natural History, was on Knowlton’s scuba diving team.

During her stay at STRI, Plaisance was also deploying devices called autonomous reef monitoring structures, or ARMS, off the coast, for the purposes of her own study. In the past few years, she has collected crustaceans—ranging in size from five millimeters to five centimeters—from dead coral heads or ARMs at depths of 26 to 39 feet in designated sites in the Indian, Pacific and Caribbean oceans. Recently, using DNA barcoding, she determined that a far greater number of crustaceans—as many as 525 different species—far higher than expected, lived in the 20.6 square feet of natural and manmade structures. The results of her globe-trotting research, a study titled “The Diversity of Coral Reefs: What Are We Missing?” is now available in the journal PLoS ONE. I caught up with her the other day to discuss the study.

What sites did you include, and how were those sites selected?

We selected the sites to span the range of diversity that we find on a reef. Typically, there are more species in the North (Lizard Island, Australia) than in the South (Heron Island, Australia) and in the West (Great Barrier Reef sites) than in the East (French Frigate Shoals, Hawaii – The Line Islands – Moorea, Frecnh Polynesia) in the Pacific Ocean. We also added two other ocean basins—the Eastern Indian Ocean (Ningaloo Reef, Australia) and the Caribbean (Bocas del Toro, Panama) that have very different evolutionary histories and biogeographies. The Caribbean reefs are very degraded and it was interesting to see how they compare with Indo-Pacific sites.

Can you explain what an ARMS is?

The ARMS were developed by NOAA in Hawaii. Basically, it is a little home for all the different species to settle in. It is about 20 centimeters with layers, completely opened or closed, for the species that prefer open layers with a lot of currents or the species that like little caves. You have all these different habitats in it. It is a great sampling device that supposed to mimic, roughly, the complexity of dead coral. We can use them in sand, grass beds, in all different sorts of habitats. We can process them very easily, and we can compare the results from site to site.

How often did you visit the sites? And, how did you go about your collecting at each?

I visited the sites once or twice depending on how and when the field trips were organized. Usually, we would dive in the morning. We tried to find live coral heads. Sometimes we were successful and sometimes not. Then, we’d take them back to the lab. I worked mainly alone, but sometimes I had volunteers helping. I would start in the lab, opening the coral head, breaking them down. It took about a day to examine the whole coral head because there were so many things living in it. I just grabbed all of the crustaceans that I could see and stored them under running saltwater. I would take the crustaceans, take pictures, record data and then take a bit of tissue for molecular studies and store the rest of the body for morphological studies later on. I didn’t do any morphological studies, but we have collaborations with people who do, so I would save the rest of the crustaceans for them. Then, I would take back to Washington only the tissues to work on the DNA sequencing.

Why did you choose to focus on crustaceans?

They are probably the most numerous group living in the coral heads. It is about half crustaceans and the rest would be mollusk and other things. Crustaceans were really diverse and abundant. But also they are very easy to sequence. Mollusks are a hassle to sequence. To avoid those technical problems, we chose the crustaceans.

How did you use DNA barcoding?

People have been using DNA barcoding now for about 10 years. It is a short sequence fragment, and we sequence the same fragment for everything. We have universal primers. It’s not that easy, of course. You always have problems. But it is easier than all the other molecular techniques right now. I sequenced that short fragment in each crustacean and then compared all those fragments for all the different species. Basically, if it is five percent different, it is two different species. If it is less than five percent different, it is the same species. So it was really easy to determine how many species we had.

In total, you found 525 different species. How many did you expect to find?

Yes. We really didn’t expect that much. Compared with diversity estimations in coral reefs, we found a lot. In the Great Barrier Reef, we had about 200 decapods, when the Great Barrier Reef is supposed to have 900—and we only sequenced [what was found in] two square meters. So it is just so much more compared to the estimates that have been published.

After I sequenced everything, I compared my sequences with the sequences that have been published and are available. Only a few of the crustaceans have been sequenced previously, and a lot of them have probably not been described yet.

What’s next for you?

The highlight of this research was really to be able to dive on the reef and witness the beauty of it. But the shocking part was to see how everything can be destroyed so fast. When we went back to Panama in 2010, the reef had bleached completely. The temperatures were really high. Where we actually had deployed the ARMS there, it was a dead zone a year later. There was nothing living anymore.

I think coral reefs are much more important than the general public knows and the government knows. They have so many threats right now, locally and globally. It is unbearable to see the destruction. That is why right now I am actually transitioning to conservation.

I am interested in the resiliency of the reefs. Reefs can undergo a phase shift. Basically, you have plenty of healthy corals and a few weeks later you just have algae that has overgrown the reef. I am trying to find solutions to reverse these phase shifts.

The Sierra Nevada de Santa Marta range in Colombia has traveled over 1,300 miles. Photo courtesy of Image Science and Analysis Laboratory, NASA-Johnson Space Center, and the Smithsonian.

The Sierra Nevada de Santa Marta, a UNESCO world heritage site just 26 miles off the Caribbean coast of Colombia, is the tallest coastal mountain in the world. It’s peak towers at 18,942 feet, and it hosts 36 different streams and rivers.

No human force—be it faith or muscle—could move such a mountain. Nevertheless, the mountain has moved.

A recent collaborative study from researchers in Colombia, Europe and at the Smithsonian Tropical Research Institute (STRI) reveals that the Sierra Nevada de Santa Marta has traveled 1,367 miles from northern Peru to its current location over the past 170 million years.

One major indicator that the mountain had moved was discovered using a technique called paleo-magnetism, which analyzes the direction in which certain types of rock crystallized. (Crystals are influenced by the Earth’s magnetic field.) “The magnetic signature of these rocks says that they cannot be from where they are right now,” says Agustin Cardona, a postdoctoral research fellow with STRI and one of the authors of the study.

The study shows that the Sierra Nevada de Santa Marta began its initial move from northern Peru due to pressure by the tectonic plates of the Pacific. Over millions of years, the mountain moved constantly, undergoing periods of more accelerated movement, and finally joining the Colombian Andes. Then, around 45 million years ago, the Pacific plates isolated the Santa Marta from the Andes, pushing it all the way out to the Caribbean coast.

By measuring the depths of specific minerals (silicon, for example) in the rock, researchers were also able to date some specific parts of the mountain. They discovered that its ancient foundation is over one billion years old, dating to the Pangean supercontinent. They also learned that the mountain contains many rock fragments that were uprooted in the course of its journey. This is likely responsible for the equally fragmented fossil record of the Santa Marta area.

“The next step is to test which fragments have moved, and which have stayed in place,” says Cardona. “Then we’ll have a truly robust paleo-geography for the region.”

With this complete geological history, Cardona says scientists will be better suited to understand the specific effects of global phenomena such as climate change on the highly biodiverse environment of the Santa Marta mountains. The mountain’s height, combined with its tropical location, has created numerous microclimates that provide habitat for many rare species, including 46 amphibian species and 628 different species of bird, not to mention unique mammals like the giant anteater and the white-lipped peccary. Some 26,500 indigenous people also live on the mountain, including the Kogi, Arhuaco and Wiwa tribes, among others. “This is a living, breathing, mountain,” says Cardona.

And the mountain is still on the move. Though the Pacific forces have stopped acting on it, the tectonic plates of the Caribbean are now pushing the mountain. The entire region is slowly shifting towards the Caribbean, and is not scheduled to stop anytime soon. Of course, we will barely notice the change during our lifetimes. But the odyssey of the Sierra Nevada de Santa Marta will continue nonetheless.

This rain frog, from the genus Pristimantis, has a distinctive red stomach that suggests it is likely a new species. Photo courtesy of Brian Gratwicke, Smithsonian Conservation Biology Institute.

According to Andrew Crawford, a former postdoctoral fellow at the Smithsonian Tropical Research Institute (STRI) and a current researcher at the Universidad de los Andes, the amphibian skin disease chytridiomycosis (known as chytrid) has already eliminated nearly 100 different frog species in Panama and threatens one-third of all amphibian species worldwide.

A recent study suggests that some frogs species were wiped out by chytrid even before scientists knew of their existence. In another new study, three new frog species have been discovered in an area of Panama not yet affected by the deadly pathogen. The newfound frogs give even more urgency to those researchers already feverishly working to save species from extinction.

The three species—including two frogs from the genus Pristimantis and a robber frog from the genus Craugastor—were discovered in the disease-free mountains of eastern Panama. In Panama and the Central American highlands, chytrid is spreading at a rate of 19 miles per year. Scientists at the Panama Amphibian Rescue and Conservation Project—an initiative sponsored by the National Zoo to save the frogs of Panama—anticipate that chytrid will soon sweep across the site, perhaps within the next six years. When it comes, it will be there to stay. And as of yet, nobody has found a way to stop it.

The amphibian disease was first detected in Queensland, Australia in 1993, and genetic evidence suggests that it was present in Africa even before that and traveled the world on the back of a carrier frog, the African clawed frog. Not susceptible to the disease, the African clawed frog is traded globally as food, as a pet and as a laboratory animal.

One bizarre use of the creature was for pregnancy tests in Europe, Australia and the Americas in the middle of the 20th century. (The frog was injected with a pregnant woman’s urine and if it spawned, well, that was like getting a plus sign.) With the advent of modern pregnancy tests, the frogs were no longer needed. Many were subsequently released or escaped into the wild, where they spread the disease. Now amphibian populations around the world are in grave danger.

“The diversity of species getting hit by this one pathogen is remarkable,” says Crawford.

The project is on the hunt for a solution, however, and its members have initiated a two-pronged approach to save threatened frog species. First, the project is attempting to capture frogs and raise them in captivity, where they can be protected from chytrid. The frogs will ideally be reintroduced to their native habitats at a later date. “We have a decent idea of susceptible species,” says Crawford, who has worked with the project. “We don’t know when we’ll solve the problem, but until then we can get those species in captivity, and try to get at least 100 to 200 individuals of a certain species, to ensure breeding potential.”

The newly discovered robber frog is one such species that is particularly vulnerable to chytrid.

The second step—finding a cure—is a bit more complicated. “Either we have to kill the fungus or make the frogs resistant,” says Crawford. “The best hope right now is finding a bacteria that can confer resistance to frogs.” Field researchers have been painting frogs with cultures of various bacteria and then testing the frogs’ resistance to chytrid in their habitat. Recently, one frog species in the infected Sierra Nevada mountains of California has experienced a high survival rate from chytrid with the help of a specific bacteria. “It’s one avenue for now that seems to show some promise,” Crawford says.

In the face of this global threat, Karen Lips, a University of Maryland wildlife biologist teamed up with Crawford to make the discovery that the disease is already killing species yet to be documented by scientists. By analyzing the genomes of frog specimens that Lips collected in the 1990s (using a technique called “DNA barcoding”), Crawford and Lips identified several previously undescribed frog species that were no longer present today in the Panamanian site where they were first collected.

As if the battle against chytrid weren’t tough enough already, evidence suggests a correlation between higher temperatures due to climate change and the increased rate of frog deaths from chytrid. “The solutions to climate change and infectious disease and contaminants are not always obvious. And these are big, wicked problems that are complex, they’re synergistic, they interact, and so if you’re dealing with problems like climate change or infectious disease, its not enough to go stake out another park,” says Lips. “The thinking has to change.”

The global reach of chytrid will require a large-scale solution. Instead of thinking globally and acting locally, as the saying goes, Crawford believes scientists and conservationists will have to do the reverse.

“It’s as if somebody were ripping chapters out of the book of evolutionary history,” says Crawford. “The truth is, if we never see it, then we never know what we’re losing.”

A Megalopta genalis, a tropical sweat bee that is about the size of a shelled peanut, digs through a soft tree branch in its nest. Photo courtesy of Adam Smith.

In Panama, at the Smithsonian Tropical Research Institute’s new neurobiology laboratory, researchers are studying how the brain of the tropical sweat bee Megalopta genalis relates to the behavior of the species’ social queens and solitary queens. The study is helping scientists make large strides in understanding the insects’ social behavior.

After observing the bees during daily activities (gathering food and laying eggs), researchers found an interesting pattern in the brain region that is responsible for learning and memory. In social bee queens, who are responsible for coordinating a social network of bee workers, a larger portion of their brain is dedicated to learning and memory than in solitary queens, who have to do much of the work themselves.

We spoke with Adam Smith, a post-doctoral fellow on the study, to learn more about the species and what makes them tick.

There have been other studies that have looked at brain size among social and non-social animals. Why did you decide to focus on bees, instead of another social species?

Of the four major groups of social insects—termites, bees, wasps, and ants—bees are the only ones with species that can switch between being social and solitary.  All ants and all termites are social.  There are both social and solitary wasps, but, at least of the species investigated to date, no single wasp species can reproduce solitarily and socially, as the Megalopta genalis bees can.

Also, the neurobiology and development of the honeybee brain is very well studied, and a few other species have been studied to a much lesser extent.  Together, these studies suggest that environmental influences, even on adult insects, influence brain development.  This led us to suspect that the social environment of the Megalopta genalis might also influence brain development.

What is the difference between social bee queens and solitary queens?

The most important similarity between the two is that they both reproduce—that is, lay eggs.  The major difference is that the social queens rarely leave their nest, and rarely forage for pollen and nectar.  They only lay eggs.  Solitary queens, on the other hand, have to do all the duties of reproduction. They must gather the food (pollen and nectar) for their offspring, as well as develop eggs in their ovaries and lay them in individual nest cells with the provisioned food. Social bee queens leave many of those duties to their workers. The other major difference between the social and solitary queens is that social queens must establish and maintain social dominance over their daughters, who stay in the nest as workers.

From the perspective of brain development, it is important to note that even social nests began as solitary nests: a female builds a nest and lays eggs, then the first generation of daughters either leave the nest to go initiate their own nests, or they stay in their natal nests as subordinate workers.  Thus, while social queens rarely forage, they had to, at one point, in order to establish their nest.  The dominance relationship associated with social nests, on the other hand, is unique to social queens.

Could you explain the social brain hypothesis, which you explored in this study?

The social brain hypothesis proposes that the complexities of social life—keeping track of dominance hierarchies, family relationships, individual identity—are so cognitively demanding that they require increased intelligence above and beyond what animals would otherwise need for the rest of their lives.

The basic prediction of the social brain hypothesis is that, all other things being equal, social species will be more intelligent than solitary ones.  However, there are a few practical problems with this.  One is that “intelligence” is not a specific trait that can be measured, so brain size, or the size of specific regions of the brain (such as the cortex in mammals) are usually measured instead.  Another problem is that “all other things” are rarely equal between species.  Even closely related species differ in a host of other traits.  Lastly, it is difficult to quantify “sociality.”  For instance, some species may live in large groups, but with little complex interaction between individuals.  Other species may live in small groups, but with long-lasting, subtle relationships between individuals.  Which of these would be more cognitively demanding?  The difficulties inherent in between-species comparisons are what motivated us to use the Megalopta genalis, because the individuals within the species are very similar.

You found that the brain region responsible for learning and memory is bigger in social bee queens. Does that mean the brain itself is bigger, or that it works differently?

The brain region was not larger in absolute terms, nor were the brains themselves larger.  What was larger was the ratio of one part of this brain region (the mushroom body neuropil) to another (the Kenyon cell bodies).  In previous studies of bee brain development, higher values of this ratio result from increased cognitive challenges, such as learning new landmark locations around the nest.  Thus, our data suggest that, as predicted by the social brain hypothesis, establishing and maintaining dominance over a social subordinate is more cognitively demanding than solitary life.

The last part of your question really hits at the heart of the matter:  We don’t know what these differences mean in terms of how the brain works—either for the previous studies, which focused on more traditional learning challenges or our own, which focused on social differences.  Future studies looking at the nature of the neural connections, rather than just the differences in brain development, are needed to figure out how the developmental differences lead to functional differences.

How is this information useful? How can it further future bee research?

In terms of future bee research, I hope it motivates more comparative studies.  For instance, many bees in the same family as Megalopta are communal, meaning that they live together, but do not have dominance hierarchies.  Do they show similar patterns of brain development? And even among the purely solitary species of bees, there are those who forage on just one type of flower, and others who gather a wide variety of pollen.  Do the latter show more flexible patterns of brain development, while the former are more “hard wired” to forage?

This study should be useful for researchers interested in brain evolution because it shows that you don’t need to just use primates, with all the logistical, ethical, and scientific difficulties they entail, to study the evolution of social intelligence.  Social insects as a group permit a wider range of comparisons than do vertebrates.

With green light sticks at the ready, Nancy Knowlton, Don Levitan and their dive team prepare for the coral spawning event. Photo by Megan Gambino

ATM blogger Megan Gambino spent a week in Panama reporting on research taking place at two locations—Barro Colorado Island and Bocas del Toro—of the Smithsonian Tropical Research Institute (STRI). Read on in this final dispatch to follow her day-to-day adventures.

Day 5 and Day 6: Coral Spawning!

By day five of my Panama trip, after a night of watching bats forage at Barro Colorado Island and two nights of diving near Bocas del Toro, I was beginning to think I was going to get a moon burn.

Only a couple of young corals “still learning the ropes,” according to coral reef biologist Nancy Knowlton, spawned on the second night dive. By the next day, the suspense was building. (Better, I thought, for the story I’ll write for the magazine!) At lunch, Nancy jokingly hit her fist on the table and said, defiantly, “It will happen.”

As the day went on, the jokes got worse. Barry “Oh Baby” White was suggested as mood music. Kylee Pawluk, one of the research assistants, suggested that before the dive we all eat aphrodisiacs, such as oysters and strawberries, to spawn the spawning. And coral reef expert Don Levitan sported his lucky red swim trunks. He asked if anyone had cigarettes for post-dive.

That night, a few more people joined the dive team patrolling the reef, as well as a camera crew that wanted to catch the spawning on video. Around 7:25, just as everyone began putting on their wetsuits, sea worms called palolo worms began spawning around the boat. The worms break in half and the tail section, containing reproductive cells, swims to the surface and releases eggs and sperm in a cloud of bioluminescence. According to the scientists, the worms’ spawning was a precursor to what the coral would soon do.

“This is it,” said Nancy. “Everybody’s in the mood for sex.”

Sure enough, at 8, just as the scientists predicted, M. franksi, the species of coral in the deeper section of the study site, began setting (fyi: that’s when the gamete bundles reach the surface of the coral, making it look pimply). The divers placed red glow sticks on setting corals, and the sea floor began to look, as Nancy had described, like “a garden of red tulips.”

Like clockwork, the coral colonies started spawning around 8:20, one triggering another triggering another. Only a couple of the late-spawning species, M. annularis and M. faveolata, spawned that night. The majority of those would spawn the next night, and as a snorkeler, I was in a better position to witness them since they are generally found in shallower water. I swam down to a large colony and watched as its gamete bundles, about two millimeters in diameter, lifted in unison.

It felt like I was in a snow globe, or maybe bubble tea.  The bundles, made up of about 100 eggs and one million sperm, slowly drifted upward, where they broke apart. I laid there among millions of tiny eggs covering the surface of the water.

Later that night, Nancy and Don explained how zygotes would form on the surface and then drift down current for about five days before settling on the bottom. Coral colonies typically grow a centimeter per year, and given that the population of the coral in the area is pretty stable, the researchers estimate that only about two coral babies from every large, 500 to 1,000-year-old coral survive. (Basically, each coral colony produces a replacement just one or two offspring for when it dies.)

“To me, coral spawning is like an eclipse of the sun,” said Nancy. “You should see it once in your life.”

The dock at STRI's Bocas del Toro research station. Photo by Megan Gambino.

ATM blogger Megan Gambino spent a week in Panama reporting on research taking place at two locations—Barro Colorado Island and Bocas del Toro—of the Smithsonian Tropical Research Institute (STRI). Read on to follow her day-to-day adventures.

Day 3: Arriving at Bocas

Today I left Panama City for Bocas del Toro, a town on Isla Colon, a 24-square-mile island on Panama’s Caribbean coast just 22 miles south of the Costa Rican border and an hour’s flight from the capital. Just outside of Bocas town is another of STRI’s research stations, where I will be staying for the next four days to report a story on a mass coral spawning that happens every year just days after the September full moon.

Since 2000, coral reef biologists Nancy Knowlton, the Smithsonian’s Sant Chair of Marine Science; Don Levitan of Florida State University; and a team of research divers have been studying the spawning of the Montastraea annularis complex—three closely related species once thought to be one and the same—here in Bocas.

Just off the coast of Solarte Island (one of the other 68 islands and mangrove keys in the archipelago)—about a 20-minute boat ride from the station—they’ve marked an 80-meter arc of coral reef with nine underwater buoys that they light at night with green glow sticks. Over the nine years of the project, they have tied pink flags to coral colonies they have witnessed spawn. (The outermost layer of coral is a community of living animals that eat, reproduce and die, thus making up the foundation of the rocky substrate of the reef.)

Each colony is also numbered with a blue metal tag and all have been mapped and genetically analyzed and identified. The researchers have found that M. franski, one of the species, spawns on average 100 minutes after sunset, typically five or six days after the full moon. The other two, M. annularis and M. faveolata, spawn about 200 minutes after sunset. The colonies use the lunar and sunset cues, and most likely a chemical cue (it’s possible they smell each other spawn), to synchronize their spawning. The latter two species cannot cross-fertilize, but M. franski and M. annularis are reproductively compatible. So the researchers have been studying what reproductive barriers or ecological conditions are in play that prevent hybridization. Also, they’re beginning to wonder, if reproductive success depends on mass spawning, then what will happen as coral reefs become few and far between as a result of the damaging effects of climate change and human development.

Wetsuits hanging to dry outside STRI's dive locker. Photo by Megan Gambino.

The team was gearing up for its first night dive. In years past, they have found that a few colonies typically jump the gun and spawn early. The group spent the morning making sure the tags on the coral were visible, while I snorkeled above to get my bearings of the study site. The next time I’d be there I’d only have a flashlight and the green glow sticks on the buoys to orient myself!

At about 5 p.m., six divers and I gathered in the lab to hear Don’s instructions. The dive team would be making two back-to-back dives, one in timing with when M. franksi spawns and the other when M. annularis and M. faveolata do. The operation was impeccably organized, like a coral raid. Armed with red glow sticks, the divers were told to crack and place them on setting corals, or corals that became pimpled with gamete bundles almost ready to be released. They were to record set and spawn times on waterproof slate boards. (On average, spawning happens about 20 minutes after the coral sets.)

In the boat, “Team Spawn,” as Don jokingly named the divers, synchronized their watches and donned life vests. At the site, we waited for sunset and then all of us made our way to the lit transect by 7:45 p.m. Pairs of divers were assigned to scan certain sections of the marked reef for setting and spawning corals, and I snorkeled above to observe.

It was my first-ever night snorkel, and it was such a different experience. At first, just having my light and the lights of the divers to follow was unnerving, but I settled into it. With their lights cast downward, the dark silhouettes of the divers made them look like aquanauts. The whole landscape was otherworldly.

When I shut off my flashlight, flipped my fins and waved my hands through the water, bioluminescence kicked up like fireworks around me. I could hear Latin music blaring from the nearby town of Bastamentos whenever I lifted my ears above the surface, and the combination of the bioluminescence, music and glow sticks created this rave-like quality—surely, I thought, a fitting scene for a coral orgy.

But no such luck. M. franksi, the early spawner of the group, held off, meaning the later spawning species would too, and so we returned to the boat, canceling the second dive. Maybe tomorrow night….

The personalized gear of Elizabeth Kalko, right, one of the foremost authorities on bats. Photos by Megan Gambino

ATM blogger Megan Gambino is spending this week in Panama reporting on research taking place at two locations—Barro Colorado Island and Bocas del Toro—of the Smithsonian Tropical Research Institute (STRI). Read on in this dispatch and in future installments to follow her day-to-day adventures.

Day 1, Part 2: A Visit to Bat Cove

Elisabeth Kalko, one of the foremost experts on bats, spends two months a year, usually March and sometime between July and October, conducting research at Barro Colorado Island. Luckily, I managed to catch her there just before she planned to head back to Germany, where she is the head of the experimental ecology department at the University of Ulm. And I couldn’t pass up her offer to take me out to “Bat Cove,” just a five-minute boat ride from BCI.

We left just before sunset and anchored in the cove. On the edge of the forest, Elisabeth explained, there is a 65-foot-tall hollow tree where Noctilio leporinus, the only bat on the island with fish as its primary diet, has a roost. Also known as the greater bulldog bat, Noctilio swoops down over the water, snatching fish in its talons. Apparently, it curls its head down to grab the fish to eat, chews it and fills its cheek pouches like a hamster. Elisabeth and a grad student working with her set up their echolocation recording equipment in the boat as we waited for dark to set in and the first bats to start foraging.

Elizabeth Kalko, photo by Megan Gambino

To put things in perspective, there are 1,100 species of bats in the world. Around 120 (over a tenth of those worldwide) live in Panama, and of those, 73, ranging in size from three grams to the notorious vampire bat that’s the size of a small puppy, can be found on BCI.  Elisabeth has worked closely on understanding the behaviors of a quarter of the 73 and probably observed 60 of them. Her interest is the various foraging strategies and other behaviors that have allowed so many species to coexist. In her research, she has found bats that live in termite nests; bats off the coast of Baja, Mexico, that forage miles into the ocean; and bats that use echolocation to find stationary prey, like dragonflies perched on leaves.

Elizabeth had a bat detector with her on the boat that could pick up the high frequency echolocation calls of nearby bats and make them audible. Slowed down, the calls sounded like the chirps of birds, and Elizabeth can recognize the species from the frequency and pattern of the calls. The chirps would come in loud on the detector, and her research assistant would cast his headlamp across the surface of the water. “Wah!” Elisabeth would exclaim as one flitted by the boat.

In the beginning, several circled the area. But as the night wore on, the activity calmed down, mostly because it was just a day or two after the full moon, and bats don’t like that much moonlight; most insects don’t come out then. It was certainly a surreal experience. I think Elisabeth put it best when, perched on the bow of the boat, looking up at the moon, she said, “So many billions of people in the world are doing the same thing, day in and day out. But we three are the only people out here, looking for fishing bats.”

An agouti, a small rodent that is related to a guinea pig, makes a surprise appearance during Megan's tour of the forest at STRI. (Photo by Megan Gambino)

ATM blogger Megan Gambino is spending this week in Panama reporting on research taking place at two locations—Barro Colorado Island and Bocas del Toro—of the Smithsonian Tropical Research Institute (STRI). Read on in this dispatch and in future installments to follow her day-to-day adventures.

Day 1: Trekking around Barro Colorado Island

After arriving in Panama City last night, I woke up early this morning and drove 40 minutes north out to Gamboa. The further I got from the city, the denser the forest seemed to grow. The transition was quite remarkable. The leaves got bigger and bigger—palm fronds drooping under their weight and fern-like leaves seemingly on steroids. It reminded me of what I had read in Elizabeth Royte’s book The Tapir’s Morning Bath just days earlier: “Here things got large, even unseemly: flower petals the size of cake plates, beetles like grenades, leaves as long as coffee tables.” Gamboa, a Smithsonian Tropical Research Institute outpost, is flanked by Soberania National Park and the Panama Canal. About 3,000 people called Gamboa home in the mid-20th century. But now the population hovers around 300, half STRI employees and half canal workers. Just beyond the town, STRI has a dock, from which they ferry researchers and visitors about 40 minutes further up the canal to Barro Colorado Island.

Once on the ferry, it was the passing freighters that were gargantuan, disproportionately tall compared to the width of the canal. Needless to say, they dwarfed our little tug. But we motored along until, around a bend, yellow stucco buildings with red roofs came into sight.

The yellow stucco buildings with red roofs is home to the Smithsonian's Panama research facility, the Smithsonian Tropical Research Institute. Photo by Megan Gambino

Situated on a hillside in a quiet cove, the field station attracts researchers from all over the world who want to study the rich biodiversity of the nearly six square mile Barro Colorado Island. (Close to half of the 220 mammal species in Panama live and reproduce in Barro Colorado Island, as well as one-tenth of the world’s bats.) To provide a quick history of the island, in 1912, the construction of the Panama Canal caused the Chagres River to rise, forming Gatun Lake and isolating the island. Eleven years later, a group of scientists convinced the governor of the Canal Zone to declare the island a biological reserve. In 1940, the U.S. Congress took control of it, and by 1946, the Smithsonian Institution became its official steward. STRI, the research station, really got off the ground in 1966. Since then, it has grown into a mini campus complete with offices, dorms, a dining hall and a visitors’ center. Researchers flock there for the biodiversity, of course, as well as the access to technology (there are seven radio towers on the island that track tagged animals) and posh (well, for field stations) accommodations.

The first person I met up with on the island was Robert Horan, a researcher from the University of Georgia, who will be working at BCI for six months to track tree frogs. He offered to guide me on a walk through the forest, and we hiked a figure eight on the trails in the northern part of the island. I saw evidence of the research being done on the island—leaf nets collecting falling leaves and fruit so that scientists can better understand the pollination schedules of little-known trees; a radio tower that collects data from tagged ocelots, agoutis and other animals; cages set as traps for ocelots in order to tag them; and heat and motion activated cameras. Hoots, chirps and howls filled the humid, earthy air, and it seemed like there was a surprise—agoutis, howler and spider monkeys, lizards, tamarin, stingless bees, land crabs and crested guan—lurking around every corner.

The two and a half hour hike, in which we spent some time wandering off trail, was certainly not the 10-cent tour, which I appreciated. Robert agreed with me: you really need to get out and sweat to write a story.

Scientists have excavated hundreds of 20-million-year-old fossils at the Panama Canal expansion sites. (Courtesy of STRI.)

There was a time when North and South America did not share a land border. Instead, a large river separated the two land masses. The animals and plants on the continents kept to themselves mostly, with the exception of the birds that refused to call any one place home.

Then, 15 million years ago, the North and South collided, volcanoes erupted and the Atlantic was separated from the Pacific. About 12-million years later, a land bridge formed between the two continents, and the animals and plants began to travel freely.

This land bridge formation occurred near the site of today’s Panama Canal, which makes the area an attractive site for paleontologists who want to learn the continental origins of individual species. Thousands of fossils, ripe for analysis, lie in the canal walls. But the scientists who want them must act fast. The Panama Canal widening project, due to be completed in 2011, has already removed 10-million cubic meters of earth, with more to come.

Teeth belonging to the three-toed browsing horse were unearthed in a Panama Canal widening site. Proof that the horse's range expanded from South Dakota to Panama 15-to-18 million years ago. (Courtesy of STRI)

Smithsonian researchers are now trying to stay one step ahead of the bulldozers. Working in collaboration with the University of Florida and the Panama Canal Authority, the scientists move in, following dynamite blasts, to map and collect fossils. As of last July, 500 fossils, from rodents, horses, crocodiles and turtles, some dating back 20-million years, have been uncovered.

“We expect the fossils that we have been salvaging to resolve some major scientific mysteries,” says Carlos Jaramillo, a Smithsonian Tropical Research Institute scientist. “What geological forces combined to create the Panama land bridge? Was the flora and fauna in Panama before the land bridge closed similar to that in North America, or did it include other elements?”

At least one answer to Jaramillo’s second question has already been found. Aldo Rincon, a paleontology intern, unearthed a set of fossilized chops belonging to the three-toed browsing horse, known to have grazed in Florida, Nebraska and South Dakota between 15-to-18-million years ago.

According to Beth King, the Institute’s science interpreter, (who was recently featured in a Scientific American podcast), the presence of this horse in Panama significantly extends the southern tip of its range from previous finds, supporting the hypothesis that the habitat was probably a mosaic of relatively dense forest and open woodlands.

There are many more fossils to be found at the Panama Canal widening site, and King expects there to be many papers published within the next five years regarding their significance.

A lone jaguar captured by a camera on Barro Colorado Island, Panama, home to the Smithsonian Tropical Research Institute. (Courtesy of Jackie Willis.)

The size of a human at the same location offers a relative comparison to the jaguar (not shown). (Courtesy of Jackie Willis.)

Dry season on Barro Colorodo Island brings sun and low humidity to the plants, animals and researchers that dwell on this scientific nature reserve in the middle of the Panama Canal.

Just the right conditions for scientists Jackie and Greg Willis to take their their annual 62-mile walk to count the island’s mammal populations.

For 27 years, the Willises have made this trek, observing dozens of exotic mammals, including pumas, ocelots, and margays. But only once, in 1983, have they seen a jaguar.

That 1983 sighting was the first time a jaguar had been spotted on Barro Colorodo Island since the Smithsonian took over its administration in 1946. Only two to three more have been seen since.

“It’s pretty amazing that in such a highly-studied little place [the island is just nine square miles and three miles across] that there’s only been a limited number of jaguar sightings,” says Beth King, science interpreter for the Smithsonian’s Tropical Research Institute.

So when a jaguar was photographed walking by a tree last week around 11 p.m., Smithsonian researchers were thrilled. The pictures were taken by a surveillance camera installed in 1994 that is wired to go off in reaction to a warm body. The photos are the first visual evidence that jaguars come to the island.

According to King, jaguar populations are shrinking and have been hunted to extinction in some places in South America. “The photo of a jaguar on Barro Colorado is a sign of hope that jaguars are still present in the area,” she says.

There isn’t an established population on the island, however. Jaguars are known to swim, and the one spotted last week is just passing by. Because of the island’s size and the presence of other predatory wildcats, an adult jaguar wouldn’t have enough to eat even if it stayed. Though it must make a nice vacation spot.