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Virginia Tech Magazine's online feature, Hok-E-News, which is updated quarterly with Web-only content, gives Web-savvy readers more news and stories about some of the exciting things happening at the university today.
 Virginia Tech study reveals predation-evolution link
by Susan Trulove
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| The fossil record seems to indicate that the diversity of marine creatures increased and decreased over hundreds of millions of years in step with predator-prey encounters, Virginia Tech geoscientists report in the proceedings of the National Academy of Science online early edition the week of Sept. 10.
For decades, there has been a debate between paleontologists, biologists, and ecologists on the role of ecological interactions, such as predation, in the long-term patterns of animal evolution.
John Warren Huntley of Asheville, N.C., a postdoctoral scientist in the Department of Geosciences at Virginia Tech, and Geosciences Professor Micha Kowalewski of Blacksburg decided to look at the importance of ecology by surveying the literature for incidents of predation in marine invertebrates, such as clams and their relatives.
"Today, certain predators leave easy to identify marks on the shells of their prey, such as clean, round holes," said Huntley. "Such holes drilled by predators can also be found in fossil shells."
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Certain predators drill clean, round holes.
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The researchers also looked for repair scars on the shells of creatures that survived an attack.
The study was conducted by looking at studies which reported the frequency of drill holes and repair scars in fossil species from the last 550 million years.
First, Huntley and Kowalewski found that predation increased notably about 480 million years ago, some 50 million years earlier than previous studies have found. "The earlier studies were based on changes in morphology--predators with stronger claws and jaws and prey with more ornamented shells. We looked at the frequency of attacks, which increased about 50 million years before the changes in armor," said Huntley.
But the most notable discovery is the observation that the incidence of drill holes and repair scars are strikingly parallel to Sepkoski's diversity curve for marine invertebrates. This diversity curve, compiled by the late Jack Sepkoski of the University of Chicago, records the origination and extinction of marine animal genera through the last 540 million years (Phanerozoic). "There is a strong correlation between predation intensity and global marine biodiversity in the Phanerozoic," Huntley said.
In their article, "Strong Coupling of Predation Intensity and Diversity in the Phanerozoic Fossil Record," the researchers offer three rival hypotheses to explain the correlation. "It's the classic problem with interpreting a correlation," said Huntley. "You have to be careful when ascribing a cause. Let's say factors X and Y are correlated. A change in X could cause a change in Y, a change in Y could cause a change in X, or X and Y could both be controlled by another factor."
The first hypothesis is that predation intensity could be driving diversity. "In this case, ecological interactions would matter in evolution," said Huntley. "Organisms evolve over the long term in response to their enemies, and with increased predation intensity more species evolve."
The second hypothesis is that as biodiversity increased, by chance predators with more complex feeding strategies evolved. "Predatory techniques like drilling and peeling shells are more evolutionarily-derived than more primitive forms of predation like whole ingestion. In this scenario you would expect to evolve sophisticated forms of predation only when diversity is high," said Huntley.
And the third hypothesis is that something else is driving both predation and biodiversity. "Some periods have more sedimentary rocks, and therefore more fossils, preserved than others," said Huntley. "There is less diversity to be observed when there are fewer fossils to study. Perhaps this sampling bias affects our ability to find samples with high predation intensities as well."
"Now we will try to pick this apart," said Huntley. "We can test these hypotheses by examining relevant linkages between predation intensity and diversity in modern oceanic environments. Also, understanding the true nature of Sepkoski's curve will help us interpret our findings. Is it biological? Is it the product of uneven sampling?"
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Innovative civil engineering application developed at Virginia Tech promises cleaner waters
by Ana Constantinescu |
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| Streams, lakes, and bays may soon be cleaner thanks to an innovative approach to managing stormwater runoff being developed at Virginia Tech and funded by the U.S. Environmental Protection Agency (EPA).
A novel software application will help engineers and planners select the most efficient and site specific methods--called "Best Management Practices" (BMPs)--of controlling the amount of pollutants that enter the receiving waters through stormwater runoff.
Pollutants are washed off the roads, parking lots, or other surfaces by stormwater, and include toxic motor oil, pesticides, metals, bacteria, and trash. The Congressional Research Service reported in 2007 that up to 50 percent of water pollution problems in the United State are attributed to stormwater runoff.
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Trash accumulates after a heavy rain.
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| The application is the product of collaboration between faculty and researchers from Virginia Tech's Virginia Water Resources Research Center, the Center for Geospatial Information Technology in the Research Division, and the Via Department of Civil and Environmental Engineering in the College of Engineering.
The new BMPs selection approach, called Analytical Hierarchy Process (AHP), will factor in dozens of site-specific criteria such as soil types, land slopes, or maintenance accessibility before choosing the optimal BMPs for a particular location.
"This technique is expected to drastically reduce the BMP selection time and will also eliminate the human error from such a complex process," says Tamim Younos, water center associate director and research professor of water resources in the Department of Geography in the College of Natural Resources who serves as project coordinator. Other project leaders include Randy Dymond, CGIT co-director, and David Kibler, professor of civil and environmental engineering.
Traditionally, the selection of BMPs has been done only by proficient stormwater experts guided by little more than vaguely written regulations, experience and intuition. "They rely heavily on past knowledge, tradition, or even personal preference for particular methods of controlling stormwater runoff," explains Kevin Young, research associate at CGIT.
Young adds that all too often personal bias has led to "cookie-cutter" solutions to very complex stormwater management needs, resulting in poor control of the pollutants.
A widely used, conventional BMP is to build detention ponds near commercial or residential areas, regardless of the actual construction site needs and conditions. "The stormwater is directed to a detention pond where gravity takes over, depositing sediment and some pollutants onto the bottom," says Younos. "The pond overflow which still may contain dissolved pollutants reaches streams, rivers and lakes, and possibly groundwater."
Other types of BMPs are trenches and porous pavement that allow the stormwater to infiltrate into the ground, vegetated wetlands and sand filters that help sift the pollutants, or proprietary stormwater technologies such as hydrodynamic separators.
The new tool will be pilot-tested on Town of Blacksburg's stormwater system and the local Stroubles Creek watershed. The AHP software will be used by the research team to select BMPs within the watershed contributing runoff to Stroubles Creek, the town's main receiving water body. Two existing computer models will then be used to simulate how efficient the selected BMPs are at removing the stormwater runoff pollutants.
"The best part about conducting a pilot test on Blacksburg is that the town will be able to implement our recommendations," says Younos. "We are very pleased by the town's enthusiasm and support for this project." Other stakeholders include the New River Planning District Commission, Virginia Department of Environmental Quality, and Virginia Department of Conservation and Recreation.
Young discussed the principles of this novel approach to managing stormwater runoff in his master's thesis, under the guidance of the late professor G. V. Loganathan.
The software will be free to use by all interested engineers and planners, localities, and BMP-review authorities and will be applicable in other states with geographic and climatic environments similar to Virginia.
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Disease-free mosquito bred to disease-carrier can have all disease-free progeny
by Susan Trulove
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A decade ago, scientists announced the ability to introduce foreign genes into the mosquito genome. A year ago, scientists announced the successful use of an artificial gene that prevented a virus from replicating within mosquitoes. But how does one apply what can be done with a small number of mosquitoes in a lab to the tens of millions of mosquitoes that spread disease worldwide?
Researchers from Virginia Tech and the University of California Irvine have demonstrated the ability to express a foreign gene exclusively in the female mosquito germline, a necessary prerequisite to future genetic control strategies in mosquitoes where all progeny of lab and wild mosquitoes will have the gene that blocks virus replication--or whatever trait has been introduced into the lab mosquitoes.
Until now, if lab-grown mosquitoes that are unable to support virus replication were to mate with wild, disease-vector mosquitoes, only half of their off-spring would have the anti-virus gene. Researchers have been working on how to skew the outcome so that all off-spring lack the ability to spread disease. However, these experiments have been hampered by the inability to express foreign genes in the mosquito germ cells.
"We needed to gain access to the cells in the reproductive germline to change the way traits are inherited," said Zach Adelman, assistant professor of entomology and a member of the Vector-Borne Infectious Disease Research Group at Virginia Tech.
Adelman discussed what the research breakthrough means for the future control of diseases spread by mosquitoes in his talk, "Dengue Viruses and Mosquitoes, Scourge of the Developing World: Can Genetic Control Make a Difference?" presented July 19 at the 2007 Biotechnology Education Conference at the Inn at Virginia Tech, hosted by the Fralin Biotechnology Center at Virginia Tech.
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The research appeared in the June 12, 2007, Proceedings of the National Academy of Sciences (PNAS), in the article, "Nanos gene control DNA mediates developmentally-regulated transposition in the yellow fever mosquito Aedes aegypti," by Adelman, assistant professor of entomology at Virginia Tech, and UC Irvine colleagues Nijole Jasinskiene, Sedef Onal, Jennifer Juhn, Aurora Ashikyan, Michael Salampessy, Todd MacCauley, and Anthony A. James.
Working with Aedes aegypti, the mosquito that carries yellow fever and dengue fever viruses, the researchers are working to create a "gene-drive system" by using instructions copied from the nanos (nos) gene, which is essential for germline formation. "Think of the nanos instructions as a key to a room," Adelman said.
Using the nanos "key," the researcher team successfully achieved germline-specific expression of Mos1, an enzyme isolated from the housefly that is a transposable element (TE)--a piece of genetic material that moves around. Mos1 can also move anything attached to it and can duplicate itself and whatever is attached to it, such as a gene that directs the dengue virus to stop replication.
"The research reported in PNAS shows that we can access the female germline and we can perform experiments in the germline," said Adelman. "The nanos control sequences show promise as a part of a TE-based gene drive system," he said.
Adelman was also a member of the team that genetically modified Aedes aegypti so that it was resistant to dengue virus type 2 and showed that the virus was unable to replicate. That research, reported in PNAS on March 14, 2006, also took advantage of the Mos1 transformation system. The anti-viral gene was activated in the mosquito gut following a blood meal. The research was a collaboration of researchers at Colorado State University and UC Irvine, lead by Alexander W.E. Franz at Colorado State. Adelman, who joined the Virginia Tech faculty two years ago, was previously at UC Irvine.
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