New DNA studies verify existence of three right whale species

02/16/05

For the first time, two types of genetic material--both nuclear and mitochondrial DNA--have been used to verify a new species designation of great whale, according to the Wildlife Conservation Society and other groups in The Royal Society's Proceedings: Biological Sciences. According to the recent study conducted by researchers at WCS, the American Museum of Natural History, Fordham University, and University of Maryland, the North Pacific right whale has been confirmed as genetically distinct from both the North Atlantic and Southern right whale, a designation with important implications for conservation efforts.

"In 2001, we compared mitochondrial DNA samples from individual whales from different ocean basins and found that the North Pacific right whales merited their own species name," said Dr. Howard Rosenbaum, researcher for WCS and the American Museum of Natural History. "Our recent analysis using both mitochondrial and nuclear DNA has produced even stronger support for this taxonomic revision, proving that both types of genetic material can be used in tandem to test and revise species classifications and subsequently redirect conservation efforts for those populations most in need."

Traditionally, mitochondrial DNA has been the preferred marker for descriptions of the genetic diversity within populations and for comparisons between different populations, in large part due to the rapid rate of sequence divergence in genetic sequences. The recent study, which used both mitochondrial and nuclear introns containing single nucleotide polymorphisms, more popularly known as SNPs, to complement one another, found that both kinds of markers support the listing of the North Pacific right whale (changed from the North Pacific population of Eubalaena glacialis to Eubalaena japonica, the North Pacific Right Whale) as its own taxon. The analysis included samples from individual North Atlantic right whales, southern right whales, and North Pacific right whales.

The study's lead author Carl Gaines, identified diagnostic nucleotide characters in the nuclear DNA for each of the three right whale species, adding to number of diagnostic mitochondrial DNA markers already reported by previous studies. For the North Pacific right whale, a total of 14 diagnostic markers were added to the existing three mitochondrial markers. Together, the datasets combined along with other analytical procedures provided researchers with the most definitive evidence for North Pacific right whales as a species. This combination of evidence was recently recommended as necessary for changing species designations for whales and dolphins by a US government convened workshop.

The agreement of both types of nuclear material in determining the status of North Pacific right whales coincides with a number of recent sightings of these rare cetaceans in the Bering Sea, where researchers working for the National Oceanic and Atmospheric Administration increased the record of known individuals from 13 to at least 25 individual animals. The survey team also spotted mother and calf pairs, an indication that this population may be increasing its numbers.

Rosenbaum added, "In addition to recent sightings and acoustical studies on the species greatly aiding in this species conservation, our genetic findings will help to support and inform additional management efforts to better protect the North Pacific right whale, one the most endangered of all great whale species."

Reaching some 50 feet in length and weighing up to 100 tons, right whales were once abundant along all land masses in the world's temperate latitudes. Right whales were among the first whale species to be hunted commercially, largely due to the fact that the animals were slow swimmers and would often float after being killed. Whalers termed them the "right" whales to hunt, soon exterminating the whales from many parts of the globe. Right whales were finally given full protection by the International Whaling Commission in 1935, but recovery for all populations has been slow at best. Hunting of right whales in the North Pacific by commercial whaling vessels continued into the 1970s causing them to nearly go extinct in this ocean basin. All species remain classified as either endangered or vulnerable according to the World Conservation Union (IUCN).

Source: Eurekalert & others

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