Note: forwarded message attached.
Do you Yahoo!?
vote.yahoo.com - Register online to vote today!
--- Begin Message ---Researchers Use DNA to Track Illegal Ivory Trade
Scientific American, September 28, 2004
Scientists have developed a new technique that can trace DNA from African elephants to within a few hundred kilometers of its geographic origin. Applying the method to DNA taken from illegally traded ivory could help limit the poaching of these endangered animals for their tusks. The work is described in a report published online today by the Proceedings of the National Academy of Sciences.
Samuel Wasser of the University of Washington and his colleagues started by collecting DNA from nearly 400 elephants at 28 reference sites across Africa. They extracted some DNA from tissue samples, but they also sampled dung, which is faster and less stressful for the animals, according to Wasser. The geographic variation of specific DNA markers was then mapped separately for savanna and forest elephants, which appear to be two separate species.
Conventional tracing techniques can only show which reference sites a new DNA sample matches best, Wasser says, but �chances are it didn't come from any of those locations.� He and his team developed new statistical methods that generate a swarm of likely locations. For a sample taken from one of the reference sites, all of the likely origins were close by. Even when the reference DNA from that site was excluded, the possibilities clustered within a few hundred kilometers of the actual origin. Wasser hopes that the results will stimulate people to collect more reference samples, especially in the forests of central Africa, to improve the technique's precision.
Once a map is created, tracing a single ivory sample costs about $100, plus labor. Wasser's team is currently analyzing a 6.5-metric-ton cache of ivory seized two years ago in Singapore. Knowing where that ivory came from should focus both legal and political efforts to prevent further poaching in the area of origin.
More importantly, Wasser says, the technique should clarify how policy changes affect poaching. In 1989, after the number of African elephants had declined from 1.3 million to 600,000 in less than a decade, the Convention on International Trade in Endangered Species (CITES) banned all international trade in ivory. CITES has recently allowed the resumption of some trade from southern Africa, where the elephant population is relatively healthy, and may make further changes when it meets in Thailand next month. Critics worry that smugglers can bring tusks into southern Africa from other regions. When they do, the new DNA-based methods should be able to help track them down. --Don Monroe
� 1996-2004 Scientific American, Inc. All rights reserved.
Geneticists Say Africa's Elephants Belong to Two Species, Not One
August 24, 2001
Biologists have long recognized morphological differences between Africa's forest-dwelling elephants and those that inhabit the savanna. But they have always considered the two types to be members of the same threatened species. The results of a genetic study described today in the journal Science, however, indicate that the elephants form distinct groups and thus merit recognition as separate species. The new findings could impact Africa�s elephant conservation efforts.
Stephen J. O�Brien of the National Cancer Institute and his colleagues analyzed DNA obtained from 195 free-ranging elephants from across Africa, as well as DNA from seven Asian elephants (which were already considered a separate species). Focusing on sequences from four nuclear genes, the team found differences between forest and savanna elephants amounting to more than half that seen between African and Asian elephants. They also detected very little evidence of interbreeding between the two African types. On that basis, the researchers propose reassigning the forest elephants from the species Loxodonta africana to Loxodonta cyclotis.
Distinguishing the forest and savanna elephants in this way could have important implications for conservation management of the two groups. Forest elephants, which are concentrated in politically unstable countries, face particularly intense pressure from human activities. "Given the rapid depletion of both forest and savanna elephant numbers in the past century and the ongoing destruction of their habitats, the conservation implications of recognition and species-level management of these distinct taxa are considerable," the authors write --Kate Wong
Experienced Female Elephants Ensure Family Survival
April 20, 2001
Matronly elephants hold the key to their family's well-being, according to a study published today in Science. These females guard the clan's social knowledge, which is essential for successful breeding.
The wisdom these gray elders possess is the ability to distinguish friend from foe among other elephant families, which they encounter about 25 times a year in the Amboseli Elephant Research Project area in Kenya. This skill is important because other elephants can harass calves or start disputes, disrupting the family.
The team of researchers, based in the U.K. and Kenya, used high-powered hi-fi equipment to replay recorded calls from other elephants and test whether matriarchs could distinguish them from their kin's calls. They then observed if, in response to the calls, the elephants huddled together and smelled the air to figure out who was coming. These tests indicated that families with older matriarchs were better at identifying who was approaching.
The results were impressive: families with matriarchs 55 years old or older were several thousand times more likely to bunch together defensively when hearing the calls of families they rarely encountered. Families with younger matriarchs (around 35 years old) were only 1.4 times more likely to bunch together in the same setting. Families led by older matriarchs also turned out to have more offspring per female per year throughout the study. This led the scientists to propose that an inability to distinguish friend from foe can leave a family on the defensive during times when they could be reproducing.
"We believe this to be the first statistical link between social knowledge and reproductive success in any species," Karen McComb, lead author of the study, explains. "The results highlight the disproportionate effect the hunting and poaching of mature animals might have for elephant populations." --Harald Franzen
--- End Message ---
_______________________________________________ Ugandanet mailing list [EMAIL PROTECTED] http://kym.net/mailman/listinfo/ugandanet % UGANDANET is generously hosted by INFOCOM http://www.infocom.co.ug/
