July 12, 2011
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September 28, 2010
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.
August 23, 2010
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.”
April 1, 2010
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.
September 16, 2009
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.”