Smithsonian Tropical Research Institute
Smithsonian Tropical Research Institute
The Smithsonian Tropical Research Institute in Panama, the only bureau of the Smithsonian Institution based outside of the United States, is dedicated to understanding biological diversity. What began in 1923 as a small field station on Barro Colorado Island in the Panama Canal Zone has developed into one of the world's leading research institutions. STRI’s facilities provide a unique opportunity for long-term ecological studies in the tropics, and are used extensively by some 600 visiting scientists from academic and research institutions in the United States and around the world every year. The work of resident scientists has allowed STRI to better understand tropical habitats and has trained hundreds of tropical biologists. Wikipedia.
News Article | May 18, 2017
By deploying green clay caterpillars across six continents, researchers unmasked an important global pattern. Their study will be published in Science on May 19. Their discovery that predation is most intense near sea level in the tropics--in places like their study sites at the Smithsonian Tropical Research Institute (STRI) in Panama--provides a foundation for understanding biological processes from crop protection and carbon storage to the effects of climate change on biodiversity. Insects drove the trend, not mammals or birds. "As someone who has studied insect biodiversity in the tropics for most of my life, I wasn't surprised that insects were responsible for most of the predation observed," said Yves Basset, leader of the ForestGEO Arthropod Initiative at STRI. The team put out almost 3,000 model caterpillars for four to 18 days at 31 different sites from Australia to Greenland at different altitudes, from zero to 2,100 meters above sea level. Based on characteristic marks left by predators in the clay, they could tell whether the models were attacked by birds, mammals or insects. Tropical sites were the most dangerous. In Greenland, the daily chances of a caterpillar model being attacked by a predator were only 13 percent of the odds at the equator. And for every 100 meters of increase in altitude, the chance of being attacked fell by almost 6.6 percent. At the highest forested site, the daily odds of a predator attack was only 24 percent of the odds of attack at sea level. "Most previous studies that didn't support the conclusion that predation is more intense in the tropics were pieced together from evidence gathered in different ways by different groups of people," Basset said. "My colleagues and I were part of a team of people from around the world who all used the same method at different sites, including a few of the ForestGEO sites. We deployed many replicates of fake caterpillars, modeled after a geometrid moth, and analyzed our results together." "This seems like a very simple experiment but the results are relevant to the way we understand some of the important processes in nature, like the innovation of defenses and how temperature changes may affect biodiversity," Basset said. "The results further emphasize the power of citizen science for simple, yet significant experiments." "Caterpillars eat plants, therefore causing crop damage and forcing plants to create new chemicals in their leaves to defend themselves," Basset said. "Caterpillars also defend themselves from predators. Our finding that predation pressure is stronger in the tropics also suggests that insects in the tropics have to be more innovative in order to defend themselves." The authors of this study represented 35 research centers and universities, including STRI; the Swedish University of Agricultural Sciences; the University of Helsinki, Finland; the Institute of Entomology, Czech Academy of Sciences; the University of South Bohemia, Czech Republic; the New Guinea Binatang Research Center; the University of California-Irvine; Eidgenossische Technische Hochshule, Zurich; the University of Texas-Arlington; the University of New England, Australia; the University of Alberta, Edmonton; the University of Iceland; the University of Sao Paolo; the University of Hong Kong; the Natural History Museum of Denmark, Copenhagen; Instituto de Ecología, Xalapa, Mexico; Escuela Politécnica Nacional, Ecuador; the University of Ostrava, Czech Republic; Zoological Society of London, the University of Oxford; the University of Turku, Finland; Chinese Academy of Sciences; the University of Aberdeen; Makerere University, Uganda; Swarthmore College, U.S.; the State Institution of Education, Zditovo, Belarus; Aarhus University, Demark; the University of Tartu, Estonia; the University of Bergen, Norway; the University of Beyruth, Germany; and the University of Lancaster, UK. The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a part of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. STRI website: http://www. . Roslin. T., Hardwick, B., Novotny, et al. 2017. Higher predation risk for insect prey at low latitudes and elevations. Science.
News Article | May 23, 2017
Female vampire bats form strong social bonds with their mothers and daughters as they groom and share regurgitated meals of blood. They also form friendships with less closely related bats. Gerry Carter, post-doctoral fellow at the Smithsonian Tropical Research Institute (STRI), and colleagues discovered that unrelated friends are important backup support when family members go missing. When they remove a major food donor, like a mother or daughter, from a bat's social network, females who previously built up more friendships with non-relatives cope better with their loss. They score more food than do female bats who only invest in close kin. "Is it better to have a few strong social bonds or a greater number of weaker social ties?" asks Carter. "Theory suggests you should always invest in the cooperative partner that provides the best returns. But clearly, a social animal should not put all its social time and energy in just one relationship, especially in an unpredictable social environment. That's like putting all your eggs in one basket." "Females don't begin reproducing until they are two years old," said co-author Gerald Wilkinson professor of biology at the University of Maryland. "They only have one pup per year, so the number of closely related females tends to be low." "Vampire bats who feed more non-relatives don't usually do better at getting fed when they are hungry," Carter said. "So why cultivate non-kin "friends"? We discovered that on the rare occasion that they lose a major food donor, they do much better. Their social network of food donors is wider and more robust." Vampire bats live on the edge. If they do not get enough to eat, it does not take long before they die of starvation. Their close relatives and friends often step in, sharing blood meals. Strengthening relationships by feeding a possible donor is one way to increase the chances of being fed. Having a larger number of potential donors is another. Carter calls the balance between these two strategies "social bet hedging". To understand how social bet hedging works for vampire bats, Carter's team monitored social interactions in a captive colony of about 30 marked common vampire bats (Desmodus rotundus) for four years. They worked out how the bats were related based on their genes. Carter removed individual females from the group for a 24-hour fasting period. Just before returning them to the group, he removed one of the bat's key food donors, usually its mother or daughter. Then he looked at how each bat coped with this change to its social network. Common vampire bats are native to the American tropics and sub-tropics, where they often feed on cattle, especially where forests have been replaced by pastureland. "It's not uncommon that a bat goes out to forage and fails to get food, and it's not uncommon that her closest relative will have switched to a different roost that night," Carter said. "We're recreating a situation that vampire bats might face fairly often." Social bet hedging might exist in other species, including our own. Other studies have shown that baboons that lose a close relative to a predator will begin grooming more individuals in their group. There is also evidence that humans are happier with quality over quantity, yet people living in unpredictable social environments tend to value more friendships over a few stronger ones. "It would be particularly interesting to test the extent to which human collaborative or friendship networks are shaped by decisions to invest in relationship quantity or quality," the authors conclude. "The social bet-hedging hypothesis provides a new dimension to why animals form and maintain social groups" said Damien Farine, a former post-doctoral fellow at STRI who is now principal investigator at the Max Planck Institute for Ornithology and University of Konstanz in Germany, and co-author of the study. Funding for this study was from the Ford Foundation and a grant from the U.S. National Science Foundation, the American Society of Mammalogists, and the Animal Behavior Society. The Smithsonian Tropical Research Institute, headquartered in Panama City, Panama, is a part of the Smithsonian Institution. The Institute furthers the understanding of tropical nature and its importance to human welfare, trains students to conduct research in the tropics and promotes conservation by increasing public awareness of the beauty and importance of tropical ecosystems. STRI website: http://www. .
News Article | May 25, 2017
—It pays to share widely, because you never know when you might need a friend to go to bat for you. At least that’s the strategy employed by the common vampire bat, according to new research. A study published Tuesday in the journal Biology Letters found that female members of the species who had previously shared their meals with a greater number of non-relatives tended to fare better during hard times than those who invested in smaller social networks. These findings add to a growing body of evidence that humans are far from alone in forming friendships, that is, preferential associations with non-relatives, social bonds that appear to run deeper than straightforward tit-for-tat exchanges. The bat’s strategy, which the researchers call “social bet hedging,” may play a role in shaping cooperative behavior in other species, including our own. “Understanding how individuals make cooperative investments based on the returns in more ‘simple’ social bonds, like in food-sharing vampire bats can help us understand the foundations of more complex relationships like those among humans,” says lead author Gerald Carter, a postdoctoral researcher at the Smithsonian Tropical Research Institute in Panama. Dr. Carter describes Desmodus rotundus, the scientific name for blood-slurping bat native to Central America and South America, as “a great organism to study for insights into cooperative relationships.” Wild females and their young will often roost in groups of eight to 12 in caves or hollow trees, which they leave each night in search of a meal, one that typically dribbles from the bites they inflict on chickens, pigs, dogs, and other animals (human blood is rarely on the menu). Because their blood-only diet contains so little fat, the bats cannot store energy for very long: Those who go two or three nights without feeding starve to death. When a female bat fails to secure a meal for herself, as happens with about a third of juvenile bats and about 7 percent of adults each night, she will groom her roost-mates in the hopes that they will regurgitate some of their partially digested meal into her mouth. Help often comes from mothers, daughters, or other kin, but bats will also often share their food with unrelated individuals – their friends. In research conducted in Costa Rica in the 1970s and 1980s, biologist Jerry Wilkinson observed bats refusing to feed roost-mates that had previously snubbed them, and he quantified the costs and benefits of such sharing. These insights, combined with the relative ease with which researchers can replicate the conditions that promote this behavior, have made the bats a model species for studying what biologists call reciprocal altruism, a behavior in which one organism makes a sacrifice to help another, with the expectation that the favor will be repaid. “The most frequent assertion is that vampire bats are exhibiting tit-for-tat,” says Dr. Wilkinson, a professor at the University of Maryland and a co-author on this newest paper. “The more recent work that Gerry Carter did for his PhD under my supervision indicates that the bats are not engaging in strict tit-for-tat, but they are reciprocating over a longer time interval.” In 2015, Carter and Wilkinson found that the bats would sometimes appear to forgive roost-mates who declined to help because they didn’t have enough food to share, and bats who had previously been unable to help would be especially generous later on, almost as though they were compensating for past stinginess. In other words, each bat appears to navigate a complex social environment, one where she must to keep track of who snubbed her – and for what reason – while also working to repair relationships that have been strained. This most recent finding, based on a four-year study of about 30 captive bats, builds on this research. Some bats feed more non-relatives than others, and those who cultivated weaker ties with a larger number of friends would usually be fed as often as those who forged stronger bonds with a few friends. But when the researchers separated a bat from her primary donor, typically her mother or daughter, the benefits of having a bigger social network became apparent. Bats who had invested in quantity instead of quality had an easier time finding donors. Their friends helped them cope with the loss. “When I very first plotted the data, I was overwhelmed with surprise and joy that it looked exactly how I thought it should,” says Carter. “That is a very rare thing in science.” “I was surprised to see such clear evidence for the value of having backup partners. We’ve not seen that before,” says Joan Silk, an anthropologist at Arizona State University who has studied social relationships among baboons. “The great contribution of this paper is that it provides evidence about a completely new way in which having relationships matter,” Dr. Silk says. “It makes sense that if relationships are important for individuals, then strategies to deal with the loss of partners may also be very important.” Like female vampire bats and humans, female baboons are known to form close ties with non-relatives, and they tend to spend more time grooming more partners following the death of a female relative. Humans tend to report greater happiness from having a small number of close friends as opposed to a larger network of weaker ties, but in environments where friends are likely to leave, quantity matters more than quality. Among humans, baboons, and bats, these strategies likely operate outside of conscious awareness: pursuing and maintaining friendships does not require any deliberate calculation of the costs and benefits. “In many situations, our first impulse is often cooperative,” says Carter. “We feel emotionally compelled to help others,” he says, “because natural selection has done the calculations for us.” “You don’t ask your friends to exchange 25 minutes of emotional support for two dinners at your house,” he says. “That’s not how friendships work at all.”
News Article | May 3, 2017
The Amazon rainforest is a treasure trove of biodiversity, containing 10% of the planet’s species in its 6.7 million square kilometers. How it got to be that way has been fiercely disputed for decades. Now, a new study suggests that a large section of the forest was twice flooded by the Caribbean Sea more than 10 million years ago, creating a short-lived inland sea that jump-started the evolution of new species. But the new evidence still hasn’t convinced scientists on the other side of the debate. “It’s hard to imagine a process that would cover such a large forest with an ocean,” says lead author Carlos Jaramillo, a paleontologist at the Smithsonian Tropical Research Institute in Panama City who has been in both camps. Researchers generally agree that parts of the Amazon were once under water, but they don’t agree on where the water came from. Those in the “river camp” argue that freshwater streaming down from the rising Andes sliced up the land below, dividing plants and animals into isolated groups that later turned into new species. The fast-growing mountains also created microclimates at different elevations, sparking speciation and funneling new plants and animals into the Amazon basin. However, when marine microorganisms were discovered in Amazonian sediments in the 1990s, some scientists hypothesized that the forest was once inundated by an ocean, which created new species as forest dwellers quickly adapted to the flood. But proving either case—the river view or the ocean view—is tough. Rocks and fossils that could paint a definitive picture are exceedingly rare. So Jaramillo and his colleagues turned to a different kind of data: cores drilled into the jungle floor. Six centimeters wide and 600 meters deep, the cylindrical cores preserve a record of the region’s past environments in the form of pollen, fossils, and sediments, going back tens of millions of years. Jaramillo used two cores: one from eastern Colombia, drilled by an oil company, and one from northeastern Brazil, taken by the Brazilian Geology Survey in the 1980s. Jaramillo’s team went through the cores layer by layer. Most of the remains came from land-dwelling species. But in two thin layers, it found marine plankton and seashells. The Colombian core even contained a fossilized shark’s tooth and a mantis shrimp, both ocean dwellers. That was enough to convince Jaramillo, who was once firmly in the river camp, that the Caribbean Sea had reached down into the western Amazon of Brazil, Ecuador, and Peru twice: once 18 million years ago, and again 14 million years ago, he writes today in . “It’s a lost ecosystem,” he says. These seas didn’t last for long. In northwest Brazil, the first flood endured some 200,000 years, while the second lasted 400,000 years. Colombia, which is closer to the Caribbean, was inundated for a longer period, 900,000 and 3.7 million years, respectively. Those floods could have been caused by the growing Andes, Jaramillo says. The mountains would have pushed down the rest of the continent as they thrust upward, letting seawater flow in. But that water would have been quickly displaced as freshwater and sediments flowed down the peaks and rebuilt the basin. In geological time, these floods lasted a mere blink of the eye, Jaramillo says, “but it’s still a long time for a tree.” Even these relatively short events would have transformed the region. The new work “makes the case [for marine flooding] much stronger, and it makes the timing more definite,” says Carina Hoorn, a geologist and palynologist at the University of Amsterdam and Ikiam Regional University of Amazonia in Tena, Ecuador, who first proposed the marine flooding theory. But Paul Baker, a geologist at Duke University in Durham, North Carolina, and Yachay Tech in Urcuquí, Ecuador, is still a firm member of the river camp. “In [Colombia], I don’t have any problem with there being a marine incursion,” Baker says. But the Brazilian core troubles him, because marine-looking plankton has turned up in other ancient freshwater lakes in Europe, he says. More convincing to Baker would be a measurement of oxygen isotopes in the shells, which could reveal whether they grew in salt- or freshwater. Jaramillo says he’s already working on it. He’d also like to find more Amazonian fossils to study species that may have gone extinct during this dynamic time. For now, there’s only one thing Jaramillo, Hoorn, and Baker can all agree on: They will need to drill and study many more cores from across the region to solve the mystery of the Amazon’s biodiversity.
Christy J.H.,Smithsonian Tropical Research Institute
Integrative and Comparative Biology | Year: 2011
Most semiterrestrial, intertidal and shallow subtidal brachyuran crabs that live in tropical and warm temperate estuaries, bays and protected coasts world-wide release their planktonic larvae near the times of nocturnal high tides on the larger amplitude tides in the biweekly or monthly cycles of tidal amplitude. Crab larvae usually emigrate quickly to the sea where they develop to return as postlarvae to settle in habitats suitable for their survival. Predators of larvae are more abundant where larvae are released than where they develop, suggesting that this migration from estuaries to the sea reduces predation on larvae. Crabs with larvae that are relatively well-protected by spines and cryptic colors do not emigrate and often lack strong reproductive cycles, lending support to this explanation. Adults control the timing of the release of larvae with respect to the biweekly and monthly cycles of tidal amplitude by controlling when they court and mate and females control when development begins by controlling when they ovulate and allow their eggs to be fertilized by stored sperm. By changing the time they breed, fiddler crabs (Uca terpsichores) compensate for the effects of spatial and temporal variation in incubation temperature on development rates so that embryos are ready to hatch at the appropriate time. Control of the diel and tidal timing of hatching and of release of larvae varies with where adults live. Females of the more terrestrial species often move from protected incubation sites, sometimes far from water, and they largely control the precise time, both, of hatching and of release of larvae. Females of intertidal species also may influence when embryos begin to hatch. Upon hatching, a chemical cue is released that stimulates the female to pump her abdomen, causing rapid hatching and release of all larvae in her clutch. Embryos, rather than females, largely control hatching in subtidal species, perhaps because females incubate their eggs where they release their larvae. Topics for further study include the mechanism whereby adults regulate the timing of breeding, the mechanisms by which females control development rates of embryos, the nature of communication between females and embryos that leads to precise and synchronous hatching by the number (often thousands) of embryos in a clutch, and the causes of selection for such precision. The timing of hatching and of release of larvae by cold-temperate, Arctic, and Antarctic species and by fully terrestrial and freshwater tropical species has received little attention. © The Author 2011. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved.
Riehl C.,Smithsonian Tropical Research Institute
Proceedings. Biological sciences / The Royal Society | Year: 2013
Cooperatively breeding animals live in social groups in which some individuals help to raise the offspring of others, often at the expense of their own reproduction. Kin selection--when individuals increase their inclusive fitness by aiding genetic relatives--is a powerful explanation for the evolution of cooperative breeding, particularly because most groups consist of family members. However, recent molecular studies have revealed that many cooperative groups also contain unrelated immigrants, and the processes responsible for the formation and maintenance of non-kin coalitions are receiving increasing attention. Here, I provide the first systematic review of group structure for all 213 species of cooperatively breeding birds for which data are available. Although the majority of species (55%) nest in nuclear family groups, cooperative breeding by unrelated individuals is more common than previously recognized: 30% nest in mixed groups of relatives and non-relatives, and 15% nest primarily with non-relatives. Obligate cooperative breeders are far more likely to breed with non-kin than are facultative cooperators, indicating that when constraints on independent breeding are sufficiently severe, the direct benefits of group membership can substitute for potential kin-selected benefits. I review three patterns of dispersal that give rise to social groups with low genetic relatedness, and I discuss the selective pressures that favour the formation of such groups. Although kin selection has undoubtedly been crucial to the origin of most avian social systems, direct benefits have subsequently come to play a predominant role in some societies, allowing cooperation to persist despite low genetic relatedness.
Wright S.J.,Smithsonian Tropical Research Institute
Annals of the New York Academy of Sciences | Year: 2010
Five anthropogenic drivers-land use change, wood extraction, hunting, atmospheric change, climate change-will largely determine the future of tropical forests. The geographic scope and intensity of these five drivers are in flux. Contemporary land use change includes deforestation (∼64,000 km2 yr-1 for the entire tropical forest biome) and natural forests regenerating on abandoned land (∼21,500 km2 yr-1 with just 29% of the biome evaluated). Commercial logging is shifting rapidly from Southeast Asia to Africa and South America, but local fuelwood consumption continues to constitute 71% of all wood production. Pantropical rates of net deforestation are declining even as secondary and logged forests increasingly replace old-growth forests. Hunters reduce frugivore, granivore and browser abundances in most forests. This alters seed dispersal, seed and seedling survival, and hence the species composition and spatial template of plant regeneration. Tropical governments have responded to these local threats by protecting 7% of all land for the strict conservation of nature - a commitment that is only matched poleward of 40°S and 70°N. Protected status often fails to stop hunters and is impotent against atmospheric and climate change. There are increasing reports of stark changes in the structure and dynamics of protected tropical forests. Four broad classes of mechanisms might contribute to these changes. Predictions are developed to distinguish among these mechanisms. © 2010 New York Academy of Sciences.
Turner B.L.,Smithsonian Tropical Research Institute
Applied and Environmental Microbiology | Year: 2010
Extracellular enzymes synthesized by soil microbes play a central role in the biogeochemical cycling of nutrients in the environment. The pH optima of eight hydrolytic enzymes involved in the cycles of carbon, nitrogen, phosphorus, and sulfur, were assessed in a series of tropical forest soils of contrasting pH values from the Republic of Panama. Assays were conducted using 4-methylumbelliferone-linked fluorogenic substrates in modified universal buffer. Optimum pH values differed markedly among enzymes and soils. Enzymes were grouped into three classes based on their pH optima: (i) enzymes with acidic pH optima that were consistent among soils (cellobiohydrolase, β-xylanase, and arylsulfatase), (ii) enzymes with acidic pH optima that varied systematically with soil pH, with the most acidic pH optima in the most acidic soils (α-glucosidase, β-glucosidase, and N-acetyl-β- glucosaminidase), and (iii) enzymes with an optimum pH in either the acid range or the alkaline range depending on soil pH (phosphomonoesterase and phosphodiesterase). The optimum pH values of phosphomonoesterase were consistent among soils, being 4 to 5 for acid phosphomonoesterase and 10 to 11 for alkaline phosphomonoesterase. In contrast, the optimum pH for phosphodiesterase activity varied systematically with soil pH, with the most acidic pH optima (3.0) in the most acidic soils and the most alkaline pH optima (pH 10) in near-neutral soils. Arylsulfatase activity had a very acidic optimum pH in all soils (pH ≤3.0) irrespective of soil pH. The differences in pH optima may be linked to the origins of the enzymes and/or the degree of stabilization on solid surfaces. The results have important implications for the interpretation of hydrolytic enzyme assays using fluorogenic substrates. © 2010, American Society for Microbiology.
Leigh Jr. E.G.,Smithsonian Tropical Research Institute
Journal of Evolutionary Biology | Year: 2010
Many thought Darwinian natural selection could not explain altruism. This error led Wynne-Edwards to explain sustainable exploitation in animals by selection against overexploiting groups. Williams riposted that selection among groups rarely overrides within-group selection. Hamilton showed that altruism can evolve through kin selection. How strongly does group selection influence evolution? Following Price, Hamilton showed how levels of selection interact: group selection prevails if Hamilton's rule applies. Several showed that group selection drove some major evolutionary transitions. Following Hamilton's lead, Queller extended Hamilton's rule, replacing genealogical relatedness by the regression on an actor's genotypic altruism of interacting neighbours' phenotypic altruism. Price's theorem shows the generality of Hamilton's rule. All instances of group selection can be viewed as increasing inclusive fitness of autosomal genomes. Nonetheless, to grasp fully how cooperation and altruism evolve, most biologists need more concrete concepts like kin selection, group selection and selection among individuals for their common good. © 2009 European Society for Evolutionary Biology.
Leigh E.G.,Smithsonian Tropical Research Institute
Journal of Evolutionary Biology | Year: 2010
Like altruism, mutualism, cooperation between species, evolves only by enhancing all participants' inclusive fitness. Mutualism evolves most readily between members of different kingdoms, which pool complementary abilities for mutual benefit: some of these mutualisms represent major evolutionary innovations. Mutualism cannot persist if cheating annihilates its benefits. In long-term mutualisms, symbioses, at least one party associates with the other nearly all its life. Usually, a larger host harbours smaller symbionts. Cheating is restrained by vertical transmission, as in Buchnera; partner fidelity, as among bull-thorn acacias and protective ants; test-based choice of symbionts, as bobtail squid choose bioluminescent bacteria; or sanctioning nonperforming symbionts, as legumes punish nonperforming nitrogen-fixing bacteria. Mutualisms involving brief exchanges, as among plants and seed-dispersers, however, persist despite abundant cheating. Both symbioses and brief-exchange mutualisms have transformed whole ecosystems. These mutualisms may be steps towards ecosystems which, like Adam Smith's ideal economy, serve their members' common good. No claim to original US government works. Journal compilation © 2010 European Society for Evolutionary Biology.