Smithsonian Tropical Research Institute Science Seminar 2005
by Eric Jackson
The Smithsonian Tropical Research Institute (STRI) is an outpost of academic excellence in an educationally underdeveloped country. This is not to deny that Panama has some towering intellectuals, nor is it to put on snotty airs of gringo superiority because the Smithsonian is, after all, a US government institution. But this is a community of scholars, most of them possessed of PhDs yet still driven to discover new things rather than to rest on their laurels as experts. And it’s too brilliant a collection of individuals to be merely American: scientists on the cutting edge of their fields come from many different countries to STRI, which is not afflicted by the insecurity which, for example, for the most part keeps foreigners off of the University of Panama faculty and tries to keep its best professors’ minds safely confined with departmental boxes.
Thinking outside the box is what brilliant people tend to do, and once a year STRI goes through a major cross-pollination otherwise known as its annual science seminar.
This year biologist Allen Herre, whose research down here includes the investigation of beneficial and detrimental cacao tree infections, organized the two-day event, which took place in the Tupper Auditorium on July 12 and 13. This reporter attended most of the presentations, but missed quite a few of them because other newsworthy things and pressing business exigencies intruded on those days. However, there was an abstract of all of the seminar talks that will be used to at least mention the presentations that were missed, because the full breadth of the topics considered is an important part of the story.
This year’s seminar started and ended by considering interactions between human beings and the tropical environment. The final presentation, by Mark Wishnie on an interdisciplinary study about reforesting Panama with native species of trees, is reported in the outdoors section of this issue of The Panama News. The seminar started out with a presentation by Dolores Piperno about her studies of plant microfossils and how they help us understand the ancient roots of human settlements, migrations and agricultural development in the tropical Americas.
This reporter missed Dr. Piperno’s presentation but was able to talk with her afterward, and the work she does is the subject of an article in the last issue of this publication. Essentially what she does is use microscopic fossilized bits of pollen, starch grains and phytoliths to examine the vegetation that has covered this region over the past 14,000 years, and from that draw inferences about the evolving relationships of people and the land and the origins of plant domestication and agriculture.
The next speaker, Rob Ewers, gave a very mathematical presentation on the relationships among economic development, market forces and deforestatation in the Amazon rainforest. The talk first analyzed the Environmental Kuznets Curve, a hypothesis that attempts to draw a relationship between Gross Domestic Product and environmental devastation, and then explained a different mathematical model that he’s developing which relates changes in world markets for soybeans, beef and tropical hardwoods with Amazonia’s deforestation rates. His conclusions were not optimistic for the future of Brazil’s forests.
Marine biologist David Kline then spoke of his research into coral diseases on reefs in Bocas del Toro and elsewhere. Noting a probably relationship between human activity and an 80 percent decline in Caribbean coral reefs over the past three decades, he said that the common notion that nitrates and phosphates washing into the sea is the main culprit behind the white band disease that devastates coral is overblown, and that the real problem is organic carbon, which feeds the pathogens that destroy coral.
Kline and his colleagues are looking at the genetics of corals to see which are vulnerable and which are resistant to diseases, and cataloguing the various bacteria that kill coral and tracing their etiologies. One of the things that’s also being examined is the possibility that antibiotics found in farm or human sewage may affect coral, either directly or indirectly by changing the mix of bacteria that interact with coral.
Entomologist Robert B. Srygley followed with a talk about his studies of butterfly migrations across Panama. Part of his work involves following the development of ever smaller flying machines, which are limited by their power supplies and thus give some insights into the energy that insects must consume during their migrations.
His work has involved following the migration of sulfur butterflies, taking butterfly censuses at Barro Colorado Island, and experiments with magnetic fields to determine whether migrating butterflies use some sort of internal magnetic compass. (And indeed, they found that butterflies are sensitive to magnetism and that probably explains how they find their way across Panama.) All of that research has led to new questions, about the relationship of El Niño phenomena and butterfly migrations, whether changes in environmental factors on the Atlantic side provoke mass flights, and whether migrations are responses to population pressures among insects.
Harvard PhD candidate Margaret Crofoot then spoke about capuchin monkeys and the relations among their social groups, as studied on Barro Colorado Island. The monkeys live in variously sized groups whose territories overlap and who can but usually don’t get into some deadly rivalries. It’s not a matter of capuchin monkeys being tolerant of outsiders. They aren’t. But it seems that they don’t fight wars over the expected thing, the availability of food. That may be because different monkey groups seem to eat different diets. But certain jungle patches where foods that rival groups both eat is exceptionally plentiful and easy to pick do attract more competition.
Crofoot doesn’t think much of the idea that monkey groups might have distinctive cultures with dietary restrictions or preferences analogous to the Bushes hating and the Jacksons loving broccoli or beef being popular in Argentina but taboo in India. Although Barro Colorado Island is a forest fragment, she thinks that the behavior she has observed is not just limited to forest remnants.
William F. Laurance then spoke about some oil company funded work he has been doing in Gabon, where hunting pressure on forest animals is often severe but not so much in a large and well patrolled Shell Oil mineral extraction area. The oil company has also built roads to serve its drilling and extraction work, which Laurance compared to roads just outside the concession area.
It seems that just a little bit of hunting will make a number of forest game species stay away from roads, while they have no such fear of roads in places where hunters are excluded.
After the first day’s lunch break, this reporter had another story to report, so the following few presentations are noted from the abstract that STRI provided.
Scott A. Mangan talked about work he is doing on the symbiotic and other relationships between various tropical plants on the one hand and the ubiquitous arbuscular mycorrhizal fungi (which are found in the soil and the plants that grow in it) on the other. Basically the research has uncovered the wide diversity of these sorts of fungi, both as to their life cycles and as to how they affect various plants.
Bill Wcislo then presented his work with nocturnal bees and the implications this has for the study of evolution. He believes that non-genetic behavior can open the door for natural selection in traits such as perceptive abilities and neurology.
Barro Colorado is the most studied tropical forest there is, but in the following presentation Liza Comita noted that mostly people have looked at large saplings and adult trees, while her four years of studies on the island have concentrated on seedlings.
University of California mycologist Gregory S. Gilbert describe canopy tower work that he’s doing in Panama and Australia to look at symbiotic fungi that live in the foliage of trees. He noted that a lot of fungi aren’t too picky about host species, but that they will be present in young trees but not adults.
Nitrogen fixing is something that one ordinarily thinks of as happening in the soil, for example when one grows a crop of peas. But Princeton’s Alex Barron has been studying tropical legumes trees, and the chemical differences that their root nodules exhibit when they shoot up through recently disturbed forest patches as compared to those found on the roots of trees in more mature stands. It seems that the root nodules of these legume trees do fix nitrogen in trees, but not all the time. There appears to be a mechanism that turns this nitrogen fixing function on and off.
Next John Christy took the audience to the intertidal zone, where he looked at courting behavior of fiddler crabs and how these crabs, and limpets, synchronize their reproductive habits to minimize predation of their young.
The day’s presentations ended with Egbert Leigh’s lecture on what a worthy tropical forest ecology theory ought to do. That is, lend itself to mathematical models that will predict its total photosynthesis activity, the proportion between above ground and below ground plant activity, and things like forest height and story structure.
On the second day this reporter was back to catch Rick Condit’s comparison of 50-hectare forest plots around the world, and the mathematical models predicting demography, diversity and stability he is constructing from these studies. It’s a heady theoretical work, considering how different the various tropical forests around the planet can be. Two things that Condit has found is that the most diverse forests tend to have the lowest variation in tree mortality and that although they don’t do worse than more common varieties, rare species are not favored by nature.
Portuguese marine biologist Helena Fortunato then took the seminar back underwater to look at the natural history of gastropod “life history strategies” and how they diverge when a barrier separates populations. As in, for example, the isthmus of Panama drifting into place to separate the Carribbean Sea from the Eastern Pacific Ocean, thus cutting off populations of mollusk species, which the fossil record tells us then led to a period of many extinctions and much speciation, from which evolved new gastropods with different reproductive strategies.
The University of Arizona’s Andre J. Riveros followed with another insect navigation tale, this one about the ways that leaf cutter ants get around and experiments in things one might do to make an ant get lost. It seems that leaf cutter ants wander back and forth in their explorations going out from the nest, but have the ability to find their way directly back, even though on the forest floor they can’t generally see where they are going. It seems that if a precocious little boy develops some ethical aversions to roasting leaf cutter ants with a magnifying class, he might divert his cruelty to more subtle methods of torture by making the critters get lost using a magnetic field. But as it seems that leaf cutter ants combine vision, magnetism and chemical scent trails to navigate, the closer to the nest the magnetic disruption is tried the less effective it will be because the other means of the ant finding its way home will kick in.
Carlos Jaramillo followed with a discussion of deep history. As in many millions of years deep, with his studies of pollen and spore diversity going back 120 million years to the dawn of angiosperms, and then looking at the changes in flora back to the time of the dinosaurs as seen by the microscopic fossil record in a coal mine in Colombia and from core samples taken during explorations for oil. The oldest tropical rainforest he has found is about 60 million years old, and he has been able to observe great biological events such as the species migrations that followed the drifting into place of the isthmian land bridge between the Americas, periods of global warming and ice ages, and times of great plant diversity and relatively monotonous uniformity. “How little we know about the modern tropics,” Jaramillo noted, “and can you imagine the paleotropics?”
“For all at last returns to the sea,” wrote biologist Rachel Carson, who is widely considered the founder of environmental journalism. And Steven V. Vollmer did get us back in the water with a report on his studies of speciation and hybridization of Caribbean staghorn coral. Noting that coral reefs lend themselves to the study of evolution, he added that in the Caribbean you can observe massive coral spawnings of several species at a time and that some of the results are hybrids rather than newly evolved species.
Using genetic studies, Vollmer noted that one of the three Caribbean staghorn coral species isn’t really a species at all, but rather a hybrid of the other two. The situation lends itself to the study of gene flow between species, which in addition to random mutations and possible other factors contributes to evolutionary processes.
But Jim Dalling got the audience back on solid ground with his talk on seed persistence as a mechanism that recruits which trees pioneer gaps in the forest canopy. He said that he had found a living croton seed at Barro Colorado that had been in the soil for more than 40 years, but that we know relatively little about seed persistence in the forest. One thing that he’s exploring is the role that certain fungi in the soil play in keeping living seeds from germinating. Might it be that when a gap opens, the fungi can’t take the changed conditions and disappear, leaving the seed to sprout?
After the second day’s lunch break, Christopher Dick spoke of some “forbidden research.” No, he isn’t sending his lab assistant Igor onto the Tupper Center roof with a lightning rod on rainy season afternoons. He’s talking about work he has been doing with Biff Bermingham and Dave Roubik about the related evolutionary processes of the long tongued Euglossini orchid bees, and the Stanhopeinae subtribe of orchids, which comprise nearly 200 of some 675 species or orchids that are exclusively pollinated by one or more of the many euglossine species. Dick’s, Bermingham’s and Roubik’s inquiry not only crosses the boundary between entomology and botany, but also gets into molecular biology, genetics and evolution, and that sort of far-reaching inquiry is problematic for certain university departments that like to divide research turf into neat little boxes.
The interdisciplinary research is looking at the possibility of a “molecular clock” that predicts the divergent nucleotide progress of species descended from a common ancestor over time, somewhat akin to the way that linguists believe they can estimate how long two related languages branched off by seeing how many new or foreign words, usages and pronunciations have been adopted.
In their work the scientists have found that the euglossine bees of Panama are similar to those of Western Ecuador and that those of the Amazon Basin also share similarities among themselves, which suggests that the Andes are a boundary that affects these bees’ evolutionary processes. Among the bees, widespread gene flow and recent speciation events. On the other hand, the “molecular clock” would indicate that the orchids date back to before the Andes arose, but after the advent of euglossine bees. It seems that the bees may be responsible for orchid diversity, by pollinating rare species.
The next speaker, Hermógenes Fernández-Marín of the University of Puerto Rico’s biology department, discussed his studies of the evolution of nest building among fungus-farming ants, and the ways that the Atta colombica leaf-cutter ants use antibiotics produces in their metapleural glands to control blights on their fungus crops. It seems that the ants don’t use the antibiotics to prevent diseases, which just as in the case when humans overuse penicillin would lead to antibiotic-resistant pathogens, but apply their medicines more sparingly to treat infections.
Susan Laurance then elevated the discussion to the skies and treetops of Amazonia north of Manaus, where she has been studying the specifics of how forest fragmentation leads to the decline of bird populations. The adverse effects of destroying development that leaves little islands of green where once there were vast unbroken forests have been known and studied for nearly three decades now.
But it’s not as simple as one might presume. What happens is that ranchers will cut down an area around a forest fragment, but after a few years of overgrazing abandon the land, creating a ring of secondary growth scrub around the forest fragment, in which some birds thrive. Thus she found that over time in fragments she studied, 37 species of birds declined but 10 increased. And it seems that the “edge effect” that has been noted is not merely one phenomenon. The edge between a forest and a cow pasture, for example, is a barrier for some birds and not so much for others, but the edge created by a road through the forest is a different sort of boundary across which some birds are afraid to fly while others have no problem.
In the next presentation Andy Jones considered the dispersal of the jacaranda tree. This species is much favored for its pretty purple flowers and the shade it creates by people who retire to farms in the Interior. It’s also favored by nature when a gap occurs in the forest canopy and gives it the light it craves.
Jacarada seeds have this thin translucent envelope that can catch the wind and allow them in a few cases to sail quite far away. This material surrounding the seed itself is also a good source of mitochondrial DNA, through which the seed can be traced back along its maternal line. And thus while it is difficult to impossible to track the precise dispersal of a jacaranda tree’s seed dispersal in a tropical forest, one can collect seeds, do DNA analyses on them and determine whether that seed is related to a particular tree. That’s the sort of work that Jones has been doing on Barro Colorado Island.
And what does one find about the relationships among jacaranda trees on Barro Colorado Island? One thing is that while seeds usually don’t travel very far from the mothers, the pollen tends to travel a lot farther from the fathers.
German botanist Bettina Engelbrecht then presented her work on the effects of drought in a tropical forest. She started by noting that the most pervasive patterns of plant dispersal in tropical forests are according to moisture, whether by rainfall or water availability in the soil. Thus it would be expected that changes in these conditions, for example due to El Niño events or changing climatic trends, would affect the vegetation mixtures in the forests. It’s easy enough to generalize that species diversity goes up with increasing rainfall and down with the increasing length of the dry season, but a good broad prediction model is far away, given that the mix of plants in a diverse tropical forest includes not only the complex relationships among these plants, but also with animals and physical forces and so on that will affect the ways that plants are distributed, their health and their abilities to compete for things like water and sunlight with their neighbors.
To be able to begin to predict what something like a longer dry season might do to a tropical forest, one must know the resistance of various plant species to drought. This is what Engelbrecht is studying. She’s looking at the drought resistant characteristics of different plants, and also studying Barro Colorado’s vegetation in light of climatic and topographical characteristics that make moisture more or less available in the island’s various ecological niches.
The seminar concluded with Mark Wishnie’s presentation, covered in more detail in our outdoors section, on a multidisciplinary study about reforestation in Panama using native species.
So what, beyond shop talk among people who are mainly in various branches of biology, does such a seminar accomplish?
First, we should not denigrate the exchange of information and ideas across narrow fields of research, nor the stimulation and encouragement that such events can have on a community of scholars.
Maybe even more important, even though The Panama News was the only Panamanian communications medium present and not nearly enough scientists, students and interested lay people not directly connected with STRI were in attendance, these sorts of exchanges still indirectly shed light among a population both in Panama and in the United States that’s largely ignorant of and often hostile to science. Yes, if a tanker accident fouls their beach with goo they may want to know whether something can be done, if they retire to the countryside they may want to know which things to plant where and if they come down with some disease they will hope for a cure, but so many people who maintain at least that much interest still reject whatever information that might suggest they change the way they’re doing things, pay more attention to astrology than astronomy and vote for politicians who dismiss spending on scientific research as frivolous.
The people who spoke at the STRI science seminar, like so many other worthy scholars in many different fields, are on civilization’s front line against the advance of a new dark age. It’s a story that doesn’t pass muster by the “if it bleeds it leads” standard of journalism, but it is most newsworthy.