Smithsonian Science » plants

Transmitters unveil long-distance movements of orchid bees

John Barrat — Thu, 27 May 2010 17:42:51 +0000

In their daily search for food, blue-green orchid bees zip through increasingly scarce patches of tropical forest pollinating rare flowers. Now, for the first time ever, researchers at the Smithsonian Tropical Research Institute are able to track the routes of these creatures by gluing tiny transmitters to the backs of individual bees. The data they are collecting is yielding new insight into the role bees play in tropical forest ecosystems.

“When people disturb and destroy tropical forest they disrupt pollination systems,” says entomologist David Roubik, senior staff scientist at the Tropical Research Institute. “Now we can track orchid bees to get at the distances and spatial patterns involved in pollination—vital details which have completely eluded us in the past.”

The team trapped 17 iridescent blue-green orchid bees called Exaerete frontalis –a species common in the rainforest. “These bees easily carry a 300-milligram radio transmitter glued onto their backs,” says Martin Wikelski, director of the Max Planck Institute of Ornithology and a research associate at the Smithsonian. “By following the radio signals with a hand-held antenna, we have discovered that male orchid bees spend most of their time in small core areas, but will take off and visit areas farther away.

One male even crossed over the shipping lanes in the Panama Canal, flew 5 kilometres, and returned to Barro Colorado Island a few days later. Such long distance flights, the researchers say, support the claim that bees are major agents of gene flow, connecting widely-dsipersed orchids or other plants which they alone pollinate, over fragmented landscapes and for an extended time. This study proves that “bees are key evolutionary players in allowing orchids and other tropical plants to evolve into diverse taxa that are each spatially rare and thus require long-distance pollination,” the researchers write.

In the past, researchers have struggled to determine the distances that bees travel by following individuals marked with paint, or using radar, which doesn’t work well when trees are in the way. “Carrying a transmitter may reduce the distance that the bees travel. But even if the flight distances we record are the minimum distances that these orchid bees can fly, they are impressive, long-distance movements,” said Roland Kays, curator of mammals at the New York State Museum and a STRI research associate. “These data help to explain how the orchids these bees pollinate can be so rare.”

The Smithsonian Tropical Research Institute, the U.S. Environmental Protection Agency, the New York State Museum and the National Geographic Society all provided support for this study. Its co-authors are affiliated with the University of Arizona, Tucson, Cornell University, EcolSciences, Inc. and the New York State Museum.

A well-defended territory is what some female hummingbirds find most attractive in a mate

John Barrat — Wed, 31 Mar 2010 17:20:21 +0000

When it comes to attracting a mate, flowers and sweets often do the trick—even for one of the world’s smallest birds—the purple throated carib, a hummingbird species native to the mountainous islands of the Eastern Caribbean. Scientists recently discovered that it is in the best interest of male purple-throated caribs to defend and maintain a territory with a high density of nectar-producing flowers. Why? Because it is the quality of this territory—rather than flashy plumage or elaborate courtship displays—that attracts the most females.

Image right: A male purple-throated carib perches on a Caribbean heliconia plant. Click to enlarge. (Photo by John Kress)

John Kress, a botanist at the Smithsonian’s National Museum of Natural History, and Ethan Temeles, an ornithologist and biology professor at Amherst College in Massachusetts, have spent several years researching purple throated caribs (Eulampis jugularis) in the wild on the island of Dominica. What they observed was unique among all bird species: successful male caribs maintained and defended territories with nectar supplies that were two to five times greater than their daily needs and also isolated part of their crop for the exclusive feeding rights of visiting females. The key to this female-only feeding area was the presence of heliconia flowers.

“This is the first time such behavior has ever been observed in a bird species,” said Kress. “Not only is the male defending a huge territory from competing males, but he’s also defending a big chunk of it exclusively for females who he is trying to attract as potential mates. He is farming the nectar for these dual purposes.”

Image left: A female purple-throated carib (Photo by Ethan Temeles)

Male and female purple throated caribs are alike in plumage, but males are considerably larger and have longer wings than females. Females, however, have bills that are 20 percent longer and 30 percent more curved than the bills of the males, meaning that they are physically able to feed from flowers that males cannot. This is also known as “sexual resource partitioning” and for the purple throated carib it applies to two species of Heliconia, a primarily neotropical genus of plants. Male caribs feed from the Caribbean heliconia (Heliconia caribaea), while females feed primarily from the lobster claw heliconia (Heliconia bihai).

This close correspondence between the physical traits of the two different heliconia flowers and the bill morphology of each sex of purple-throated carib strongly suggests that the process of coevolution (the evolution of two or more species that interact closely with one another, with each species adapting to changes in the other) is the cause of this fit between the birds and the flowers. Furthermore, this process is strongly reinforced by the fact that the different energy requirements of the male and female carib are uniquely matched by the energy rewards in the nectar of their respective heliconia flowers.

Image right: A male purple-throated carib sips nectar from a Caribbean heliconia plant. (Photo by Ethan Temeles)

The scientists report that a female’s choice of a male depends on the nectar supplies within his territory, which in turn depended on his prevention of nectar losses to competing male purple-throated caribs and other nectar feeding intruders.

“One of the most important aspects of maintaining an abundant nectar crop for the male carib is keeping intruders out,” Temeles said. “We found that males that were most successful at defending their territories from intruders also were the ones that were most successful at dominating neighboring males and at feeding on neighbors’ territories.”

The male’s reward for spending the time and energy in defending his territory was, of course, the attraction of potential mates. Temeles and Kress observed that the rates of female intrusions to feed on defended territories were highest in late morning and early afternoon, at times when the amount of nectar in undefended plants was lowest. “Once the females are in the territories they are allowed to “sip from the male’s wine cellar.” If she likes what she is sampling, then mating takes place,” Temeles said.

Kress and Temeles plan to extend their studies to other islands in the Eastern Caribbean to test how this plant-pollinator system has evolved in different regions and in different ecosystems. —Johnny Gibbons

Smithsonian ecologist John Parker discusses his work with invasive plants and white-tailed deer

John Barrat — Fri, 19 Mar 2010 18:48:59 +0000

Medieval book is important resource for how plants were once collected, treated and used

John Barrat — Thu, 04 Mar 2010 17:52:09 +0000

Among its treasures, the Bibliothèque de France in Paris holds a great many splendidly illustrated books on medieval herbs and medicines. One of these manuscripts is latinus 9333, which recently was reproduced in facsimile with a volume of study. Alain Touwaide, Historian of Sciences in the Department of Botany at the Smithsonain’s National Museum of Natural History, contributed three chapters in the study volume highlighting the history, importance and originality of the manuscript.

Latinus 9333 is the Latin translation of the so-called Tacuinum sanitatis, a medieval handbook on wellness written in Arabic by the 11th-century physician ibn Butlan. It deals with factors influencing human health: from the air, the environment and food, to physical exercise and sexual activity.

Image: The manuscript of Paris, Bibliothe`que nationale de France, latinus 9333: f. 36 verso: Ocimum basilicum L.; and f. 37 recto: Mandragora officinarum L.

In contrast to the Arabic original, several copies of the Latin version are illustrated. Characteristically, these illustrated Tacuinum sanitatis come from northern Italy and date to the 14th century. Their illustrations include scientific representations of plants and other substances used as medicines, as well as illustrations featuring other factors that influence human health. The illustraions offer snapshots of medieval daily life, environment and activities.

Such images are of particular importance to the history of botanical knowledge and illustration, Touwaide points out in the study volume. Plants are represented here in great detail, inserted into their environment, be it natural or human. Many of the images include human figures and illustrate the way plants were collected, treated, used, or were embued with cultural meanings. They constitute material of great interest for the study of the interaction between men and plants.

The manuscript encapsulates a knowledge and wisdom gained by trial and error over centuries, often going back to a much earlier period. The archeology of its text brings to light the odyssey of medicine and science in the Mediterranean and beyond, as latinus 9333 moved from Italy further north, where its Latin text was translated into German.

Camera traps & radio collars reveal hoarding strategies of the South American agouti

John Barrat — Wed, 02 Dec 2009 14:53:22 +0000

Rabbit-sized with squirrel-like habits, the agouti of Central America is a hoarder and a robber. When not collecting fallen nuts and burying them in shallow holes, the agouti is adept at finding, stealing and re-hiding nuts buried by its neighbors. A single nut, in fact, might be hidden and stolen multiple times. The agouti’s method of seed dispersal and caching “is critically important for tropical trees, it gives seeds a much better chance for germination,” says Roland Kays, a mammalogist at the Smithsonian Tropical Research Institute in Panama, and curator at the New York State Museum in Albany.

Photo: An agouti on Barro Colorado Island with a palm nut.

Hoarding seeds is also important for the agouti, Kays says. “People may not realize it but in certain seasons food is scarce in the tropical jungle. Just as squirrels in North America hide acorns to survive snowy winters, agoutis hide nuts in the tropics to survive periods when little food is available.”

In a series of ongoing experiments on Barro Colorado Island in the Panama Canal, Kays and other researchers are using camera traps, radio collars and palm nuts with tracking transmitters attached to them to take a closer look at the nut-hoarding strategies of the agouti. “On the jungle floor there can be quite a lot of seed-cache thievery,” Kays explains. “We wanted to learn how the agouti’s methods of hiding seeds take into account such things as pilfering, scarcity of seeds and seed size.”

Video: An agouti wearing a radio collar hides seeds set out by researchers. Yellow string attached to the seeds make them easy for the scientists to locate on the forest floor. This video is composed of a series of camera-trap images.

The researchers found that where less food is available, agoutis spread their seed cashes more widely, making it harder for pilferers to find the nuts they hide. “To hide nuts further away from the tree where they are found requires more energy, yet an animal benefits when fewer of their caches are found by pilferers,” Kays says. “In lean areas competitors increase their foraging and the hoarders are left with no other choice but to spend more time in hiding seeds or lose them to thieves.”

Sequence also plays a role in seed dispersal the researcher found. In taking seeds from a tray laid on the ground by researchers, the agoutis hid the first seeds they removed closer to the tray than the seeds they took later on.
And finally the researchers learned larger seeds are hidden with more care than smaller seeds. “In terms of energy value, a larger seed is more valuable and worth the extra effort to hide it,” Kays explains.

“It is interesting that a rodent can be doing this,” Kays points out. “It is ingrained in the calculations of the daily life of an agouti to make these optimal decisions.”

The research paper “Scatter Hoarding of the Central American agouti: a test of optimal cache spacing theory,” can be found at the Web address: http://snurl.com/tek7x

Prehistoric pollination: Sawfly mouthparts fit tubular channels of gymnosperm cones

John Barrat — Fri, 06 Nov 2009 17:40:15 +0000

Scientific evidence shows that almost all of the earliest angiosperms (flowering plants) were pollinated by insects. Whether such a relationship existed between insects and early gymnosperm species (non-flowering plants with exposed seeds, such as conifers) has been widely disputed. Smithsonian scientists and colleagues, however, have recently found evidence that gymnosperm plants shared an intricate pollination relationship with scorpionfly insects 62 million years before flowering plants appear in fossil records. The team’s findings are published in the scientific journal Science, Friday, Nov. 6.

Illustration: Eurasian mid Mesozoic scorpionflies feeding on gymnosperm ovulate organs, each with tubular access to deeper-seated rewards such as nectar or pollination drops. (Illustration by Mary Parrish)

Conrad Labandeira, paleoentomologist at Smithsonian’s National Museum of Natural History, and team members examined both the specialized features of scorpionfly mouthparts and the unique reproductive features of coexisting gymnosperm plants. The proboscis (elongated tubular mouthparts) of these insects, which was up to 1.3 centimeters long, was either hairy or had ridges, and frequently had pads at the tip to suck up fluids, similar to the structure of modern hoverflies, moths and butterflies. The presumed gymnosperm hosts bore deep funnel-like or tubular channels, also up to 1.3 centimeters long, containing nectar-like pollen drops.

The reproductive anatomy of the plants was typically gymnospermous, but show important modifications for insect attraction, similar to modern flowering plants. However the lineages of these plants and their scorpionfly pollinators became extinct during the mid-Cretaceous period (approximately 105 million years ago) just as flowering plants and their newly evolved pollinators, such as moths and butterflies, came on the scene.

Photos: Lichnomesopsyche gloriae (Mecoptera: Mesopsychidae), from the late Middle Jurassic of northeastern China, showing head and long, hairy proboscis. (Photos by Wenying Wu)

“This exciting discovery now answers the conclusions that paleobotanists were making recently regarding ‘strange’ structures occurring in the ovulate organs of some Mesozoic gymnospermous plants,” said Labandeira. “One such fructification of an extinct Early Cretaceous cheirolepidiaceous conifer family, Alvinia bohemica, is the best example of an anatomically complicated, jerry-rigged device to achieve insect pollination. There were contemporaneous, matching, elongate insect mouthparts, and other evidence, that indicate presence of a gymnosperm-based pollination mode from the deep past.”

The evolution of this type of elongated mouthpart among insects occurred at least five separate times during a 13-million-year span during the Middle Jurassic period. The pollinating relationship between modern pollinators and flowering plants was an independent evolutionary occurrence, separate from the scorpionfly and gymnosperm plants.

Mangroves research by Candy Feller, Smithsonian Environmental Research Center botanist

John Barrat — Mon, 05 Oct 2009 05:54:07 +0000

Salad science: Coaxing caterpillars to reveal the secrets of their leafy desires

admin — Tue, 15 Sep 2009 17:50:07 +0000

Hold your chef’s knife Emeril. You too Wolfgang and Rachael Ray. Insect ecologist Eric Lind is in the kitchen. Toss him a handful of poison ivy or kudzu and he’ll whip up fare fit for…a caterpillar.

Photo: A woolly bear caterpillar.

Lind is a postdoctoral research fellow in the Terrestrial Ecology Lab at the Smithsonian Environmental Research Center on the Chesapeake Bay. Along with his advisor, John Parker, he’s trying to figure out the taste buds of the woolly bear caterpillar (Pyrrharctia isabella), a common insect herbivore in the Mid-Atlantic. Lind and Parker want to know if these fuzzy eaters prefer to chomp invasive or native plants. It’s a question related to biodiversity.

Ecologists around the world are concerned with preserving native plants and trees. In the temperate forest surrounding SERC about two thirds of the understory ground cover is comprised of non-native plants. Lind and Parker want to know if these exotic plants have a competitive advantage over native plant species, because woolly bears and other herbivores find them distasteful.

Testing caterpillars’ taste buds is no simple task. Just like your local salad bar, plants in the wild come in different shapes, textures and flavors. Herbivores rely on each of these cues to tell them what to eat. Deciphering this code is Lind’s task. He’s examining 40 different plant species – half invasive, half native.

First he measures the physical and nutritional elements of the plants. Then he isolates and tests the flavor alone.

To do this, Lind follows one master recipe. He’s actually tasted it, multiple times. It is equal parts cellulose, wheat germ, and then the key ingredient: carefully-extracted plant essence. He tosses in a pinch of agar, pours in boiling water, mixes and viola: plant paste aux poison ivy. Or mile-a-minute weed. Or kudzu. You get the point.

For each plant-flavored paste, Lind also prepares a plain version, minus the plant essence. This is his control. He spreads the mixtures into long, thin, molds and lets them firm up until they look and feel something like a fruit rollup. Then, Lind chops each rollup into pieces about the size of a thumbnail, roughly the amount of food a woolly bear eats in a day.

Photo: Posion ivy

Now it is time for the hungry caterpillars to feast. Each woolly bear gets two carefully-weighed servings: one plant-flavored, one plain. They dine in the peace and quiet of a temperature-controlled incubator. When they’ve had their fill, Lind weighs the leftovers and records the data.

Lind’s data quickly piles up. When the feeding trials finish, he’ll begin the hard work of statistical analysis. Lind is careful not to make any predictions, “You can always convince yourself you see differences in the data. The question is whether or not they’re significant.” Caution-aside, Lind hopes this experiment will offer scientists a richer understanding of the relationship between exotic plants and the native herbivores that may or may not munch on them. —Tina Tennessen

New Acquisition: Namibian specimens come to the herbarium of the National Museum of Natural History

John Barrat — Thu, 03 Sep 2009 15:28:35 +0000

A collection of nearly 800 flowering plants was recently acquired by the Botany Department of the Smithsonian’s National Museum of Natural History from the National Botanical Research Institute in Windhoek, Namibia, Africa. The collection includes nearly 160 specimens from the Compositae, or sunflower family. “These specimens are especially welcome because we don’t have many collections from Namibia,” Smithsonian Curator Vicki Funk says. Compositae is the largest family of flowering plants in the world with nearly 25,000 recorded species and is the subject of a new book sponsored in part by the Smithsonian.

Photo: Compositae specimens from the Namibian collection.

How did the Smithsonian come to acquire this magnificent collection? Herbaria periodically skim their collections and when duplicates are found they are offered up to other institutions as gifts for exchange. Typically, based on the needs of their research collections, institutions trade specimens for other specimens. In this case, Esmerialda Klaassen, researcher at the National Botanical Research Institute, was interested in what books the Smithsonian might have to trade.

“We don’t have any plants they want because a lot of herbaria focus mainly on their own regional flora,” Funk explains. At the National Museum of Natural History “we try to maintain a global collection because we ask questions on a global scale.”

For the exchange, the Namibian herbarium chose two volumes of the plant encyclopedia, Families and Genera of Vascular Plants, by Klaus Kubitzki and Clemens Bayer. In return, the Smithsonian received four shipments of Namibian Compositae totaling 800 mounted specimens. This new acquisition adds to the Botany Department’s herbarium collection of some 5 million processed specimens that have been collected from around the world.

Photo: Sara Alexander, a George Mason University graduate student working at the Smithsonian’s National Museum of Natural History, looks over some of the recently acquired plant specimens from the National Botanical Research Institute in Namibia. (Photos by Vicki Funk)

Funk says that “Each piece of puzzle helps us figure out what’s going on globally, and such contributions make the Smithsonian collection that much richer.” More plants from Namibia are expected in exchange for additional books. Funk concluded that “This is a wonderful way to help our colleagues in other countries and at the same time acquire very interesting material for our herbarium.” —Jessica Porter

Fossils Show Prehistoric Global Warming

John Barrat — Fri, 22 May 2009 12:52:32 +0000

The Past as Prologue
For those who think that global warming is a 21st-century phenomenon, Scott Wing, a scientist at the Smithsonian’s National Museum of Natural History, has news about the past.

Wing headed an international team of scientists whose discovery of plant fossils in the Bighorn Basin of northwestern Wyoming helps document the consequences of a sudden global warming, called the Paleocene-Eocene Thermal Maximum (PETM), 55 million years ago.

Experts believe the PETM, which was caused by a massive release of carbon into the atmosphere, may be an analogue for what is happening today as humans burn increasing amounts of fossil fuel and release large amounts of carbon dioxide.

Plant Movement Signals Global Warming
For nearly 15 years, Wing and his team dug through sediments deposited during uplift of the Rocky Mountains, looking for fossils of the right age and condition. Their discoveries proved that warming caused major shifts in the distribution of plants, allowing southern-dwelling trees and shrubs, related to poinsettia, sumac, and paw-paw, to move some 1,000 miles north in less than 10,000 years. These subtropical invaders flourished for about 100,000 years in what we now know as Wyoming. As carbon dioxide levels dropped and temperatures cooled again, plants related to birches and bald cypress came to dominate the vegetation.

The study and interpretation of this fossil record helps other scientists project future changes in plant life that may result from global warming induced by human activity.