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Measuring Biodiversity and More: PLoS Biology Press Release

October 20, 2004

Biodiversity: measuring up to the loss

Species are disappearing faster than biologists can identify and document them. Mindful of this crisis, nearly 200 countries (under the Convention on Biological Diversity) agreed to staunch the loss of biodiversity by 2010. However, to meet this goal, biologists need reliable metrics to monitor global trends in biodiversity. In the open access journal, PLoS Biology, Stuart Butchart from Birdlife International, Cambridge, UK, and others from Conservation International, IUCN and the Institute of Zoology, London, describe a new way to generate such an index that can measure trends in extinction risk for complete classes of organisms, starting with the world's 10,000 bird species. Their "Red List Index" measures changes in overall extinction risk over time for all bird species worldwide and shows "a steady and continuing deterioration in the status of the world's birds between 1988 and 2004," with "particularly steep declines" in recent years for Asian birds-resulting from massive deforestation in Indonesia-and for seabirds such as albatrosses and petrels, which drown on the hooks of commercial long-line fisheries.

Butchart et al. focus on evaluating trends in changes in threat status (extinction risk) by tracking the shift of individual species between the categories developed by the World Conservation Union (IUCN) Red List. Species are placed in categories on the Red List ranging from extinct to "least concern," according to criteria that take into account their population size, population trends, and range size. Thousands of scientists from around the world feed these assessments, which have been widely used to measure the degree of degradation of biodiversity.

Butchart et al. argue that Red List Indices complement indicators based on population trends, because although the indices show coarser temporal resolution, they have much better geographic representation; they're based on nearly all species in a group worldwide rather than on a potentially biased subset. The Red List Index therefore provides a reliable baseline to track progress toward the 2010 target, not only for birds but for all groups of organisms.

Citation: Butchart SHM, Stattersfield AJ, Bennun LA, Shutes SM, Ak'§akaya HR, et al (2004) Measuring global trends in the status of biodiversity: Red List Indices for birds. PLoS Biol 2 (12): e383.

The published article will be accessible to your readers at: http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020383

Press-only preview of the article: http://www.plos.org/downloads/plbi-02-12-butchart.pdf

Related image for press use: http://www.plos.org/downloads/plbi-02-12-butchart.jpg

CONTACT:
Stuart Butchart
Birdlife International
Cambridge, UK
+1223-277-318
+1223-277-200 (fax)
stuart.butchart@birdlife.org


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A Clear View of Mycobacterial Infection

Fighting an infection might seem to be a battle between David and Goliath, given the relative sizes of bacterial infectious agents and the animals they infect. But on closer examination it is more often a chess match between two skilled opponents who have the uncanny ability to anticipate each other's moves. An example is provided by the interaction between Mycobacterium tuberculosis, which causes tuberculosis (TB), and its human host. One of the host's first moves against the mycobacterium is the formation of a granuloma, an aggregate of cells, which consists of macrophages and other defensive immune cells. Although granulomas are required for the elimination of the infection, Lalita Ramakrishnan and colleagues have now shown that the bacteria have a game plan of their own.

One problem in understanding the interaction between the mycobacterium and the host has been that it occurs deep in the lung of the infected animal. To overcome this limitation, Ramakrishnan and colleagues used zebrafish embryos, which are transparent and can be infected by a relative of the TB pathogen, M. marinum. This enables the researchers to watch cells as they are recruited into the granuloma.

By visualizing in zebrafish infections of a virulent strain of M. marinum and a strain missing a genetic region called RD1 - a region that is somehow involved in the virulence of the bacteria - Ramakrishnan and colleagues have observed that RD1 is actually required for granuloma formation and even recruits more macrophages to granulomas. This might seem an odd strategy, as macrophages are required for mycobacterial elimination. But in this ongoing chess match, the virulent mycobacterium exploits the host's defense-granuloma formation-by providing additional macrophages for the bacteria to infect.

The end game of the chess match remains unclear. While granulomas are required for protection against mycobacteria, they are not completely effective. Thus, these bacteria have developed a strategy to recruit the normally defensive cells of the host to their advantage, but it remains to be shown what tips the balance between the macrophages' ability to clear the infection and their unwitting participation in the development of TB.

Citation: Volkman HE, Clay H, Beery D, Change JCW, Sherman DR, et al (2004) Tuberculous granuloma formation is enhanced by a Mycobacterium virulence determinant. PLoS Biol 2 (11): e367.

The published article will be accessible to your readers at: http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020367

Press-only preview of the article: http://www.plos.org/downloads/plbi-02-11-ramakrishnan.pdf

Related image for press use: http://www.plos.org/downloads/plbi-02-11-ramakrishnan.jpg

CONTACT:
Lalita Ramakrishnan
University of Washington
Seattle, WA USA
+1-206-616-4286
+1-206-616-1575 (fax)
lalitar@u.washington.edu


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Predicting Infection Risk of Mosquito-Borne Disease

Malaria, which is transmitted by mosquitoes, remains one of the greatest threats to global health, infecting more people than ever before. Understanding how the risk of catching a mosquito-borne infection varies depending on the environment is an important step in planning and implementing effective control measures. The rate at which humans become infected is determined by how often they are bitten by mosquitoes and the proportion of mosquitoes that are infectious. It is often assumed that if the percentage of infectious mosquitoes increases, so will the rate at which humans get bitten. But in a new study published in the open access journal PLoS Biology, David Smith, Jonathan Dushoff, and F. Ellis McKenzie challenge this assumption. Using a mathematical model, the authors show that the rate at which humans are bitten and the proportion of infectious mosquitoes peak at different times and places, revealing that the standard metric of estimating the risk of infection -- the average number of times an infectious mosquito bites a person per day -- is flawed.

The distribution of humans and suitable habitat for mosquito larvae varies across the landscape. And the density of mosquito populations varies seasonally, rising and falling with changes in rainfall, temperature, and humidity. Temporal and spatial variations in mosquito populations affect the rate humans get bitten, the number of infectious mosquitoes, and the risk of infection. The mathematical model that Smith and colleagues developed predicts that human biting rate is highest shortly after mosquito population density peaks, typically either near breeding sites or where human density is highest. The proportion of infectious mosquitoes, on the other hand, reflects the age of the mosquito population: it peaks where older mosquitoes are found-farther from breeding sites-and when populations are declining. The combination of these factors results in, for example, the surprising prediction that the risk of infection can be lowest just outside an edge of town.

By mapping larval habitats against the local risk of mosquito-borne infections, Smith and colleagues conclude, epidemiological models can be developed to predict risk for local populations. Their results make the case that mathematical models can help public health officials calculate risk of infectious diseases in heterogeneous environments-that is, real world conditions-when vector ecology and the parameters of transmission are well characterized. Any plan to prevent and control the spread of mosquito-born infections would clearly benefit from paying attention to mosquito demography and behavior.

Citation: Smith DL, Dushoff J, McKenzie FE (2004) The risk of a mosquito-borne infection in a heterogeneous environment. PLoS Biol 2 (11): e368.

The published article will be accessible to your readers at: http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020368

Press-only preview of the article: http://www.plos.org/downloads/plbi-02-11-smith.pdf

Related image for press use: http://www.plos.org/downloads/plbi-02-11-smith.jpg

CONTACT:
David Smith
National Institutes of Health
Bethesda, MD USA
smitdave@helix.nih.gov


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THE FOLLOWING RESEARCH ARTICLES WILL ALSO BE PUBLISHED ONLINE:

Perception, Action, and Roelofs Effect: A Mere Illusion of Dissociation

Paul Dassonville and Jagdeep Bala challenge a prominent hypothesis that proposes the existence of two separate visual systems within the brain, one creating perception and the other guiding action.

Citation: Dassonville P, Jagdeep B (2004) Perception, action, and roelofs effect: a mere illusion of dissociation. PLoS Biol 2 (11): e364.

The published article will be accessible to your readers at: http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020364

Press-only preview of the article: http://www.plos.org/downloads/plbi-02-11-dassonville.pdf

CONTACT:
Paul Dassonville
University of Oregon
Eugene, OR USA
+1-541-346-4956
+1-541-346-4911 (fax)
prd@darkwing.uoregon.edu


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Motifs in Brain Networks

Analysis of characteristic patterns of connectivity in neuroanatomical datasets suggests that nervous systems evolved to maximize functional repertoires and support highly efficient integration of information.

Citation: Sporns O, Kotter R (2004) Motifs in brain networks. PLoS Biol 2 (11): e369.

The published article will be accessible to your readers at: http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020369

Press-only preview of the article: http://www.plos.org/downloads/plbi-02-11-sporns.pdf

CONTACT:
Olaf Sporns
Indiana University
Bloomington, IN USA
+1-812-855-2772
osporns@indiana.edu


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Representation of Attended Versus Remembered Locations in Prefrontal Cortex

Persistent activity of neurons in an area of the frontal lobe-the prefrontal cortex-is often proposed to underlie short-term memory. Mikhail Lebedev and colleagues provide an alternative explanation.

Citation: Lebedev M, Messinger A, Kralik J, Wise S (2004) Representation of attended versus remembered locations in prefrontal cortex. PLoS Biol 2 (11): e365.

The published article will be accessible to your readers at: http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020365

Press-only preview of the article: http://www.plos.org/downloads/plbi-02-11-lebedev.pdf

CONTACT:
Mikhail Lebedev
Duke University
Durham, NC USA
+1-919-684-1236
+1-919-668-0734 (fax)
lebedev@neuro.duke.edu


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Unanticipated Antigens: Translation Initiation at CUG with Leucine

Proteins have been identified for which a unique translational machinery makes use of unconventional start codons.

Citation: Schwab S, Shugart J, Horng T, Malarkannan S, Shastri N (2004) Unanticipated antigens: translation initiation at CUG with leucine. PLoS Biol 2 (11): e366.

The published article will be accessible to your readers at: http://www.plosbiology.org/plosonline/?request=get-document&doi=10.1371/journal.pbio.0020366

Press-only preview of the article: http://www.plos.org/downloads/plbi-02-11-shastri.pdf

CONTACT:
Nilabh Shastri
University of California
Berkeley, CA USA
+1-510-643-9197
+1-510-643-9230 (fax)
nshastri@socrates.berkeley.edu


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