Greater than the sum of its parts

Nov 17, 2015

It is rare for a new animal species to emerge in front of scientists’ eyes. But this seems to be happening in eastern North America.

LIKE some people who might rather not admit it, wolves faced with a scarcity of potential sexual partners are not beneath lowering their standards. It was desperation of this sort, biologists reckon, that led dwindling wolf populations in southern Ontario to begin, a century or two ago, breeding widely with dogs and coyotes. The clearance of forests for farming, together with the deliberate persecution which wolves often suffer at the hand of man, had made life tough for the species. That same forest clearance, though, both permitted coyotes to spread from their prairie homeland into areas hitherto exclusively lupine, and brought the dogs that accompanied the farmers into the mix.

Interbreeding between animal species usually leads to offspring less vigorous than either parent—if they survive at all. But the combination of wolf, coyote and dog DNA that resulted from this reproductive necessity generated an exception. The consequence has been booming numbers of an extraordinarily fit new animal (see picture) spreading through the eastern part of North America. Some call this creature the eastern coyote. Others, though, have dubbed it the “coywolf”. Whatever name it goes by, Roland Kays of North Carolina State University, in Raleigh, reckons it now numbers in the millions.

The mixing of genes that has created the coywolf has been more rapid, pervasive and transformational than many once thought. Javier Monzón, who worked until recently at Stony Brook University in New York state (he is now at Pepperdine University, in California) studied the genetic make-up of 437 of the animals, in ten north-eastern states plus Ontario. He worked out that, though coyote DNA dominates, a tenth of the average coywolf’s genetic material is dog and a quarter is wolf.

The DNA from both wolves and dogs (the latter mostly large breeds, like Doberman Pinschers and German Shepherds), brings big advantages, says Dr Kays. At 25kg or more, many coywolves have twice the heft of purebred coyotes. With larger jaws, more muscle and faster legs, individual coywolves can take down small deer. A pack of them can even kill a moose.

Coyotes dislike hunting in forests. Wolves prefer it. Interbreeding has produced an animal skilled at catching prey in both open terrain and densely wooded areas, says Dr Kays. And even their cries blend those of their ancestors. The first part of a howl resembles a wolf’s (with a deep pitch), but this then turns into a higher-pitched, coyote-like yipping.

The animal’s range has encompassed America’s entire north-east, urban areas included, for at least a decade, and is continuing to expand in the south-east following coywolves’ arrival there half a century ago. This is astonishing. Purebred coyotes never managed to establish themselves east of the prairies. Wolves were killed off in eastern forests long ago. But by combining their DNA, the two have given rise to an animal that is able to spread into a vast and otherwise uninhabitable territory. Indeed, coywolves are now living even in large cities, like Boston, Washington and New York. According to Chris Nagy of the Gotham Coyote Project, which studies them in New York, the Big Apple already has about 20, and numbers are rising.


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18 comments on “Greater than the sum of its parts

  • There is a similar situation with the American Ruddy Duck cross breeding with European ducks, with back-crossing and general mixing of the genes to have the hybrids progressively replace the original European species. Conservation measures are trying to prevent this.

    http://www.ncbi.nlm.nih.gov/pubmed/17257118
    The ruddy duck, Oxyura jamaicensis, was introduced to Great Britain in the mid-20th century and has recently spread to other Western European countries. In Spain, ruddy ducks hybridize with the globally endangered white-headed duck, Oxyura leucocephala. We assessed the effects of hybridization on the Spanish white-headed ducks, which constitute 25% of the global population of this species, using a panel of eight nuclear intron markers, 10 microsatellite loci, and mtDNA control region sequences. These data allowed parental individuals, F(1) hybrids, and the progeny of backcrossing to be reliably distinguished. We show that hybrids between the two species are fertile and produce viable offspring in backcrosses with both parental species. To date, however, we found no extensive introgression of ruddy duck genes into the Spanish white-headed duck population, probably due to the early implementation of an effective ruddy duck and hybrid control programme. We also show that genetic diversity in the expanding European ruddy duck population, which was founded by just seven individuals, exceeds that of the native Spanish white-headed duck population, which recently recovered from a severe bottleneck. Unless effective control of ruddy ducks is continued, genetic introgression will compromise the unique behavioural and ecological adaptations of white-headed ducks and consequently their survival as a genetically and evolutionary distinct species.



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  • I don’t think this is as a result of speciation; rather, it’s hybridisation.

    Nonetheless, it’s great stuff, and a perfect example of “the survival of the fittest”; but is that the fittest species or the fittest individuals? I think it’s probably both.

    I’ll probably get jumped on for saying that last, but I don’t give a toss, as long as I can learn from it.



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  • Stafford Gordon
    Nov 18, 2015 at 11:20 am

    I don’t think this is as a result of speciation; rather, it’s hybridisation.

    What we have, is speciation as far as a split into sub-species, then crossing and hybrids back crossing (back crossing is the hybrids breeding with the pure parent populations).
    This provides a large mix of genetic material in the hybrids in varying proportions from both sub-species, on which natural selection can then work.

    Back-crossing, can also feed back small amounts new genetic material into the gene-pool of parent populations. (Humans with 4% of Neanderthal genes comes to mind)



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  • “Survival of the fittest” is not a good way of expressing mechanisms of evolution. Sometimes the most “fit” individual fails to reproduce due to chance (predation, disease, accident, or climatic extremes). In addition, the least “fit” individual might be successful. Which individuals survive to reproductive maturity and produce offspring is a stochastic process.

    Individuals of one species that can survive and reproduce more successfully than individuals of another closely related sympatric species and may eventually cause extinction of the less successful species (unless there is some character displacement that make the coexistence of the two species possible while sympatric).

    In plants, hybridization can in a few cases can produce a new species. However that type of speciation is rare in animals (such as seen in whiptail lizards that reproduce by parthenogenesis). Successful survival of hybrids between two different species depends on how close the two species are genetically. Horses crossed with donkeys produce mules that are more hardy than either parental types, however only one female mule was found to be fertile.



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  • You’re absolutely right cbrown, but I used the phrase in the full knowledge that it was coined by Herbert Spencer and Darwin disliked it; it is of course an excellent example of survival of the form that will leave the most copies of itself in successive generations. What I find astonishing is that it’s occurred over a very short period of time indeed, evolutionarily speaking.

    Although Black Caps have also evolved very quickly over the last fifty years or so, due partly to the use of garden bird feeders in the UK.

    Actually, the best way I know of describing it is as non random survival of randomly occurring self replicating information.

    Or something like that; you get my drift.



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  • Black Caps

    An article about these birds was posted moons ago; can’t remember – are they evolving, or adapting to warmer winters, hence hanging around for free seed?

    U.K. black caps (females have chestnut crowns) have a pleasant appearance and song (RSPB provides a sound clip), however, are there any other species suffering as a consequence of higher number B.C.s? Every bird fills some kind of niche.



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  • Environment and evolution are binary of course, but the introduction of garden feeders in the fifties added a direct human influence, in that, as with Darwin’s famous finches, which incidentally, are housed a few hundred yards away from where I live, the ones who inherited thin beaks could poke them through the mesh of the feeder and get at the goodies, which obviated the need for them to fly south to Spain in winter; and of course weather weirding or climate chaos are bringing pressures too.

    Apparently they’re found overwintering as far North as Finland now.



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  • I’ve never had a problem with survival of the fittest. It always meant if you are fit for the situation you are in you survive. The story invented for my children was a plant with a fault on its leaves that prevented full photo synthesis. All the other plants laughed at it because it was weak. As the climate changed, it got hotter and hotter with less cloud cover and the plants that had full green leaves soon began to suffer and the one with spots thrived.

    This gave them an insight into climate change and survival of the weakest (fittest). They said ‘shut up dad we are twenty and twenty two not three”.



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  • What I find astonishing is that it’s occurred over a very short period
    of time indeed, evolutionarily speaking.

    Stafford, as you probably know, Gould strongly supported the theory of punctuated equilibrium, an evolutionary process that could produce new species in relatively short periods of time. One requirement however was that these brief bursts of speciation occurred in very small populations. Would tat apply to Black Caps population size?



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  • “One requirement however was that these brief bursts of speciation occurred in very small populations. Would tat apply to Black Caps population size?” I don’t know cbrown.

    I’m not sure, but I think that theory has been discarded; if necessary, I’m certain someone here will correct me.

    As far as I can make out, it was a human intervention that helped trigger the changes; the introduction in the UK in the fifties of garden feeders; a kind of inadvertent form of breeding I suppose.

    However, strictly speaking, speciation only occurs when two communities of a single species have been seperated for so long, by for instance a mountain range or a stretch of sea, that mutational changes have become too great for any individuals within one group to mate with any in the other group; they’ve become different species.

    In the case of the coywolf the changes have come about by means of interbreeding between species; hybridisation happens all the time, it’s just not always picked up on, as in this instance.

    That’s my understand in any case.



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  • Stafford Gordon
    Nov 20, 2015 at 7:09 am

    However, strictly speaking, speciation only occurs when two communities of a single species have been seperated for so long,

    Speciation is frequently a slow (by human scales) continuous process, with diminishing fertility between divergent groups rather than a distict cut-off point.

    by for instance a mountain range or a stretch of sea, that mutational changes have become too great for any individuals within one group to mate with any in the other group; they’ve become different species.

    They do not necessarily have to wait for mutations to occur. Quite often there are numerous pre-existing mutations which are being selected against in a particular environment.
    If the environments change, different mutations will be selected against, with different repressed ones possibly eliminated from the separate populations.

    For example recessive mutations causing blindness, while fatal in surface dwelling fish, can persist and spread in cave fish populations, or those in the darkness of the deep ocean, where not developing eyes, is simply an energy saving matter rather than a severe disability.



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  • Alan4, I’m re-reading James Watson’s excellent and enjoyable book ‘DNA’, so the recessive gene is something that’s I’ve just been reminded of; and my word, as Ian Drury said, “There aint ‘alf been some clever bastards!”.

    What happened to Rosalind Franklin was tragic though.



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