Daniel Cressey reports in Nature
that the battle over the legal status of the grey wolf as an endangered species is still continuing in the United States, but he does not fail to mention another debate that is far more interesting, from a scientific standpoint.
The main question is whether the wolf that currently lives in the Western Great Lakes area merits a place on the list of endangered species. One group of conservation biologists claims that the wolf populations have recovered, and are therefore no longer endangered. Other conservationists however, claim that the wolves that are there now are not the same species as the wolves they have replaced.
The complication stems from differences in opinion of what constitutes a species. Traditionally, when two types of organisms cannot breed and create fertile offspring, they are considered two different species. This view is not held by all biologists. Some consider two types of organisms who do not usually interbreed as separate species, and there are other views as well.
Subspecies are considered part of the species, but the differences with the main species or other subspecies are more distinct than those typically found between varieties.
Modern genetics does not make it any easier to decide what constitutes a species. From a purely genetic standpoint, species don't make all that much more sense than races, since we now know that the lines between species are very blurry at best. The living world is much more a continuum of genetic material than a collection of distinct species. The view of the living world as a collection of distinct species is most likely a remnant of ancient creationist myths that claimed that some supernatural being created them separately and distinctly.
In the case of the wolf in the Western Great Lakes area, there are two species about which there is no discussion: the grey wolf (Canis lupus
) and the coyote (Canis latrans
). There more discussion about the eastern wolf, which may be a separate species (Canis lycaon
) or a subspecies of the grey wolf (Canis lupus lycaon
Wolves in the US were put on the list of endangered species in 1973 when their numbers had dropped to just a few hundred, after more than a century of hunting. Probably as a result of this measure, the population around the Great Lakes bounced back to about 4,000 individuals. They were removed from the endangered list in 2007 after the Fish & Wildlife Service had declared them a distinct population segment.
The American Humane Society did not agree and started a case that led a court in Columbia to return the Great Lakes wolves to the endangered species list on September 29, 2008.
The issue remains controversial, however.
Robert Wayne of the University of California, Los Angeles, and Jennifer Leonard, of Uppsala University in Sweden, published a genetic analysis on October 23 of last year showing that the wolves that current live in the Great Lakes area are largely a mix of the grey wolf (Canis lupus
), the coyote (Canis latrans
) and hybrids of these two.
According to them, only 31% of the wolves there today are the same species as the original population, the population they call the Great Lakes wolf. They had established the haplotype(1) of mitochondrial (2) DNA of 17 dead wolves of a hundred years ago, and compared that with the current populations. Therefore, their conclusion is that the Great Lakes wolf has not recovered and still belongs on the list of endangered species.
However, David Mech, a researcher with the US Geological Survey's Northern Prairie Wildlife Research Center in Jamestown, North Dakota, accuses Leonard and Wayne of "crying wolf" and he refutes their position in this week's Biology Letters.
"The Federal Government spends millions of dollars on the wolves when they could be used on other species," says Mech. "If the animal is recovered, as I believe the wolf is, the money could be better spent on other species." Mech's standpoint is that Leonard and Wayne used a small and incomplete set of historical samples and compared that to a subset of the current wolves in the Great Lakes area and that this has led to a bias in their analysis.
In turn, Leonard and Wayne, in the same issue of Biology Letters, accuse Mech of wishful thinking, and while they admit that most genetic studies of wild vertebrates can be questioned on sampling grounds, they also claim that their sampling method was solid, an
Mech says that Leonard and Wayne's survey missed Great Lakes wolves living there today. He also says that the study used a small and geographically incomplete set of historical samples to establish the genetic profile of the original wolf population, introducing a bias into their analysis.
Tyler Wheeldon, a masters student at Trent University in Ontario, Canada, has made his own analysis, which will also be published in Biology Letters. He used additional historical samples and now concludes that the population of wolves in the Great Lakes area is fairly similar to the situation in the 1900s and that it is therefore no longer endangered.
"Today we have a large top predator which is not coyote-like, which is what they wanted to restore," says Wheeldon. "If you have a recovered population that is filling the role of the wolf, we shouldn't worry if it's exactly what used to be there."
(1) A haplotype is a specific combination of gene(2) alleles(3). The haplotype can be used to identify specific populations of a species, because they will more closely resemble each other than populations of the same species that live in a more distant area.
(2) A gene is a piece of DNA that encodes a particular protein.
(3) An allele is a particular variation of a gene.
(4) Mitochondria are organelles (cell components) that produce energy (in the form of ATP) for the cell. They reproduce independently from the cell inside the cell, and contain their own genetic material (DNA).