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Image right: Didemnum vexillum, a sea squirt species believed to have originated near Japan that was recently discovered in Sitka, Alaska. (Photo courtesy USGS)

The grant is one of five regional grants totaling $2 million awarded by the National Sea Grant College program to prevent and control aquatic invasive species. “Invasive species in our waterways are threatening ecosystems from coast to coast — from tunicates on the West Coast and Australian spotted jellyfish on the East Coast to the round goby in our Great Lakes,” NOAA Sea Grant Director Leon Cammen said. “These grants will help to reduce the great ecological and economic costs of aquatic invasive species.”

This video shows D. vexillum tendrils hanging from a float in Orleans, Mass. (Courtesy USGS)

A non-native species, Didemnum vexillum, was discovered in Sitka, Alaska, earlier this year during a Marine Invasive Species Bioblitz organized by the Smithsonian Environmental Research Center, Alaska Department of Fish and Game, Alaska Sitka Tribe, University of Alaska, NOAA and San Francisco State University. A notorious fouling organism on boats, fishing nets, docks, and buoys, D. vexillum (also known as the carpet sea squirt) is of major concern because it grows rapidly and can completely cover aquaculture nets, shellfish beds and sensitive marine environments. Believed to have originated near Japan, the species spreads through both sexual reproduction and fragmentation, which aids in its ability to colonize new areas rapidly.

Image left: Sitka harbor, Alaska (Photo by Robert A. Estremo)

D. vexillum could have been introduced to Alaska through ballast water, fouled commercial and recreational boat hulls, relocating fouled piers and docks, fishing equipment and aquaculture gear. Now that it has been identified in Sitka, it is important to keep D. vexillum from spreading to other parts of Alaska. Several agencies are now working in conjunction with the Smithsonian to develop a rapid response plan for D. vexillum and efforts are underway to determine the extent of its distribution.

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Image left: A switchgrass moth adult (Photo by Paul Johnson)

In an recent article in the journal Zootaxa, researchers from the Smithsonian Institution, South Dakota State University and the University of Nebraska, for the first time described the immature stages of the insect species Blastobasis repartella, first described in scant detail from two male specimens of the adult moth collected in Denver, Colo., in 1910. The article re-describes the adult insect far more closely and discusses some aspects of its biology in relation to its host plant, switchgrass. Blastobasis repartella bores into the stems of switchgrass.

The insect has gain come to the attention of agricultural scientists because native grasses like switchgrass are being considered as candidates for the large-scale production of cellulosic ethanol, a next-generation biofuel.

Image right: David Adamski

Already in May 2004 at the Dakota Lakes Research Farm of South Dakota State University, professor Arvid Boe, a forage and biomass grass breeder, and postdoctoral research associate DoKyoung Lee estimated that up to 40 percent of new tillers of a few scattered plants of switchgrass were lost to the caterpillar of the switchgrass moth.

Paul Johnson, curator of SDSU’s Severin-McDaniel Insect Research Collection and a research associate in the Entomology Department of the Smithsonian’s National Museum of Natural History in Washington, D.C., collected adult moths using simple emergence traps in 2008, and estimated their population densities. SDSU scientists first suspected the stem-borer might be a new species. But David Adamski, entomologist with the USDA’s Agricultural Research Service, research associate at the Smithsonian, and a specialist in small moths, ultimately identified the insect.

Image left: Arvid Boe in a switchgrass plot maintained by South Dakota State University. (Image courtesy South Dakota State University)

Adamski is the lead author of the journal article. Professors Paul Johnson and Arvid Boe, both of South Dakota State University, are co-authors, along with J.D. Bradshaw of the University of Nebraska-Lincoln and Alan Pultyniewicz of Columbia, Md.

The journal article notes that while some Blastobasis species feed on various grasses, Blastobasis repartella “appears to be restricted to switchgrass.”

If farmers grow switchgrass as a biomass crop in the future, Johnson says, it is very likely that switchgrass moth populations will increase along with the acres devoted to the grass. This means it is very likely that agricultural producers will want researchers to develop insect control regimens to limit damage to energy crops.

Image right: Paul Johnson with insect traps in a field of switchgrass. (Image courtesy South Dakota State University)

The journal article notes that switchgrass larvae are presumably inactive during the coldest months. They were found to be active in South Dakota when plants were brought into the greenhouse in early spring and forced into early growth. In the field, mature larvae are commonly found actively feeding in late May.

Adults of Blastobasis repartella are nocturnal with a peak of activity during the pre-sunrise hours. In eastern South Dakota, adult activity occurs primarily from mid-July to mid-August. Seasonal peak adult activity related to reproductive behavior was measured by the frequency of arriving males (40–50 males per night and occasionally exceeding 75 males per night) at cages containing calling females.

There is no evidence to suggest the occurrence of a second generation or overlapping cohorts in either South Dakota or Illinois populations, the researchers say. This is consistent with the single per year growth of switchgrass and appears to correlate with geographic variations in growing season differences of switchgrass, Boe said.–Lance Nixon, South Dakota State University

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A 48 million-year-old fossilized leaf has revealed the oldest known evidence of a macabre part of nature – parasites taking control of their hosts to turn them into zombies.

The discovery has been made by a research team led by David Hughes of the University of Exeter in England, who studies parasites that can take over the minds of their hosts; Conrad Labandeira from the Smithsonian’s National Museum of Natural History; and  Torsten Wappler, from the Steinmann Institute in Germany.

Image right: An ant killed by a fungal parasite is shown here biting into a leaf vein. The fungal growth can be clearly seen issuing from the ant’s head. (Photo by David P. Hughes)

All manner of animals are susceptible to the often deadly body invasion, but scientists have been trying to track down when and where such parasites evolved.

“There are various techniques, called a molecular clock approach, which we can use to estimate where and when they developed and fossils are an important source of information to calibrate such clocks,” Hughes says.

“This leaf shows clear signs of one well documented form of zombie-parasite, a fungus which infects ants and then manipulates their behavior.”

The fungus, called Ophiocordyceps unilateralis, appears to take over the mind of infected ants – causing them to leave their colonies and head for a leaf which provides the ideal conditions for the parasite to reproduce.

Image left and below: This 48-million-year-old leaf fossil from Messel clearly bears the tell-tale scars of ants that have been infected with the mind-controlling fungal parasite. (Photo by Torsten Wappler)

When the ant gets there it goes into a ‘death grip’– biting down very hard on the major vein of a leaf. This means that when the ant dies, its body stays put so the fungus has time to grow and release its spores to infect other ants.

The death grip bite leaves a very distinct scar on the leaves. This prompted Hughes, Labandeira and Wappler to search for potential evidence of the fungus at work by studying the fossilized remains of leaves.

After studying leaf fossils from the Messel Pit, a site on the eastern side of the Rhine Rift Valley in Hesse, Germany, they found clear evidence of the death grip bite in a 48 million-year-old leaf specimen.

“The evidence we found mirrors very closely the type of leaf scars that we find today, showing that the parasite has been working in the same way for a very long time,” Hughes explains.

“This is, as far as we know, the oldest evidence of parasites manipulating the behaviour of their hosts and it shows this parasitic association with ants is relatively ancient and not a recent development.

“Hopefully we can now find more fossilised evidence of parasitic manipulation. This will help us shed further light on the origins of this association so we can get a better idea of how it has evolved and spread.”

The paper, Ancient death-grip leaf scars reveal ant-fungal parasitism, was published in a recent edition of Royal Society journal Biology Letters. –Research News, University of Exeter

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Right and below: T. flexuosa growing on power lines in Panama (Photos courtesy Gerhard Zotz)

Recently, botanists Gerhard Zotz of the Smithsonian Tropical Research Institute and Stefan Wester of the University of Oldenburg in Germany decided to take a closer look at these high-wire bromeliads. They were interested to find out how the growth and survival rates of these plants on electrical cables compared to the growth and survival of plants of the same species growing in trees–their natural environment.

During a two-year study the pair surveyed some 1,400 T. flexuosa specimens living on 1250 meters of electrical cable, as well as nearby plants of the same species growing on tree limbs. The cables were 8.25 millimeters in diameter and consisted of multiple aluminum wires woven around a single steel cable, giving them a rough surface upon which the seeds and plants can cling. Before their study the scientists observed that most of the cable-growing T. flexuosa lived on cables near roads, leading them to theorize that the dust kicked-up by cars and other vehicles provided adequate nutrients for the plants to flourish.

Although the high-wire T. flexuosa appeared to be thriving, Zotz and Wester found the cables were actually a hostile environment for the plants. T. flexuosa on power lines grew slowly, suffered a high mortality rate and were not very successful in establishing new recruits. On electric cables the death of established plants greatly exceeded the recruitment of new plants from seeds.

For these bromeliads the primary problem with cable-life, the scientists found, is a lack of water. While individuals growing on both cables and trees utilize rainwater, the zero water-absorbing properties of an aluminum cable combined with greater exposure to the sun and wind, make cable life for bromeliads highly risky. Even though dust from cars should provide an abundance of nutrients to the cable-living bromeliads, lack of water prevented them from taking advantage of this benefit.

In addition, the scientists found that even though the cables had a rough surface, the plants had a difficult time anchoring themselves to the cable. Many of the plants disappeared during the course of the study, dislodged from the cables by wind and other natural forces.

The study, the first to examine the growth and survival of electric-cable growing bromeliads, was published recently in the Journal of Tropical Ecology. –John Barrat

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Flowers are usually associated with butterflies, but not the Dutchman’s Pipe (Aristolochia grandiflora). This deciduous vine, native to Brazil, has large flowers that emit an odor of decaying flesh, which attracts flies and beetles. The insects then have to navigate the twists and turns of the flowers throat, which is covered with hairs that trap the insects inside. It is only when an insect removes the pollen sack that the hairs collapse, releasing the insect which will likely be fooled by another pelican flower into pollinating it.

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“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.

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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

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