March 19, 2013
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.”
February 29, 2012
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.
February 7, 2012
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
January 27, 2012
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.”
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.
November 10, 2011
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.