No phurkeys or turkants in our future
I was asked by my editor, presumably with tongue in cheek, if I would comment on the possibility that the farm-raised pheasants in Sharon that escaped during the October snowstorm might interbreed with wild turkeys and develop a new species. As ring necked pheasants are an Asiatic game bird and genetically far removed from the American turkey, I am sorry to say that “phurkeys” or “turkants” are an impossibility under the known laws of science.The ability of individuals to produce fertile offspring is fundamental to the definition of a species. It can take thousands of generations (perhaps 50,000 years) for a slow-maturing species like the Alaskan brown bear, for example, to evolve to the point where it is truly separate from its Asiatic relatives across the Bering Strait. If an Alaskan grizzly were to mate with a Russian bear today, the result would be another brown bear like its parents. Each bear population is now geographically isolated, and has been so in the 13,000 years since the connection between North America and Asia was severed. They are experiencing different genetic pressures and mutations and, given enough time, they will become reproductively incompatible and constitute different species. It will just take thousands more generations of isolation to bring this about.There are fewer than 400 northern right whales left in the wild. A separate right whale species exists in the Southern Hemisphere. Scientists estimate that the southern right whale has not interbred with the northern species for between 3 to 12 million years. There is also a North Pacific right whale that is more genetically similar to the southern species than its north Atlantic cousins, and this makes sense when you consider that the Arctic ice cap has until recent decades been an effective barrier to circumpolar movement. With global climate change this is no longer an absolute barrier to a viable northwest passage connecting Pacific and Atlantic waters. In fact, it has already happened.There was once a North Atlantic gray whale population, but it was hunted to extinction. There is an eastern North Pacific gray whale species, however, and one of these showed up in the Mediterranean Sea off Tel Aviv last year. An Arctic route is the most plausible explanation for how this animal reached Israel. We have evidence in our own state of a similarly epic journey of repopulation by an extirpated species, in the cougar that traveled in less than two years from the Black Hills of South Dakota to Milford, Conn., where it was struck and killed by a motorist. If a gray whale can make the journey, perhaps a North Pacific right whale will one day do the same, though it would not be able to breed with the resident species after eons of genetic isolation.Evolution can sometimes accelerate in isolated populations. This is the so-called island effect that produced dwarf mammoths in Siberia and Darwin’s finches in the Galapagos. On the other end of the evolutionary spectrum, habitat fragmentation can also lead to less genetic diversity. This is why conservation biologists are often concerned about maintaining local populations at the edges of their contiguous ranges, such as our own eastern timber rattlesnakes. When a den becomes isolated by habitat loss or poaching that prevents individuals from mating with snakes within a meta population, it loses genetic variation. This can create evolutionary bottlenecks, and in species with low numbers and poor reproductive success like the timber rattlesnake, it can accelerate the process toward extinction.Genetic diversity is just as important in wild plant and animal species as it is in those we have cultivated or domesticated for food. Lack of genetic variation in a species weakens resistance to pests and pathogens. A less diverse ecosystem without its full compliment of species occupying its available habitat niches will see some predominate and out compete others. Losing a key predator can lead to population explosions that ultimately degrade habitat, such as happens now in areas with high numbers of white-tailed deer. While the genetic differences between American wild turkeys and Asiatic pheasants make them unable to produce fertile offspring, those between coyotes and wolves in North America are still close enough that our eastern coyote picked up some wolf DNA as the animals expanded their range to occupy the predator niche once held in the northeast by wolves and cougars. They are already bigger and more gregarious than their western cousins and constitute a fertile hybrid. Someday, given time and habitat connectivity, they may replace the pure coyote strain that developed on the plains. Our descendants may be around to witness results of such speciation, though by then we might not recognize them as ours. Tim Abbott is program director of Housatonic Valley Association’s Litchfield Hills Greenprint. His blog is at greensleeves.typepad.com.