GENETICS DEFINE A DOG
Using wolf-size photos, dog judge-geneticist explains how the dog in your life evolved from hybrids, cross-breeds and the intriguing influence of wolf or dingo!
WHAT IS THE DOG GENETICALLY?
HOW THE DOG IS DEFINED BY SPECIES
Fred Lanting, All-Breeds/Sieger/Schutzhund, SAAB Member
There is genetic confusion on breeds of dogs and dog-like animals due to the different use of words such as hybrid, cross-bred, varieties, and species.
Many dictionaries inadequately define hybrids as being “individuals produced by breeding (crossing) different races, varieties, species, etc.” Disagreements arise when we do not agree (even temporarily) on the same definition. If you include wolves and domestic dogs in the same grouping because there is no hindrance to one fertilizing the other and resulting in equally-fertile offspring, then I cannot agree to call the result a hybrid. No more than Chinese and Caucasian children are hybrids. A better term for either might be “mixed” (we use the term “mixed-breed” in speaking of dogs, but usually “mixed heritage” re humans).
Since canids mate and produce offspring which in turn are just as fertile, I feel it is wrong to call them hybrids. Dingoes, coyotes, wolves, and domestic dogs are all really breeds of Canis (dogs, canids). Their offspring should not be called hybrids, but rather “crosses” just as we would call a Cockapoo a “cross.”
In my experience, “hybrid” mostly has been used to refer to the offspring of two animals capable of producing live-viable offspring but which are usually sterile themselves because of different numbers of chromosomes.
These are usually the result of mating different species or sub-species, i.e. tiger x lion; horse x donkey; zebra x donkey; camel x llama; and possibly bovine x bison (not always sterile). My use of this definition is based on my training as a scientist but as I said, people discussing a subject must first agree on which definitions they will use during their conversation so this is my concept of “hybrid.”
Certainly, animals that most people consider as being different species (cat/dog, cow/horse, reptile/bird, etc.) cannot result in viable embryos if combined somehow, whether in a test-tube or in utero. Quoting a Wikipedia article, “the exact definition of the term ‘species’ is still controversial." Biologists have proposed a range of more precise definitions, but the definition used is a pragmatic choice that depends on the particularities of the species. Likewise, there is much confusion over definitions for “canine, canid, canis, hybrids, species, family, genus, breed, dog, wolf,” and related terms.
Thus, it behooves writers to set out at the beginning, just what they mean by key words in their discussions. I am as guilty as anyone in assuming that the readers will have the same definitions that I grew up with, or that I see in dictionaries and college texts. If you want to claim that a wolf and a dog are different species (and therefore any offspring would be hybrid), say so at the beginning. You will find very few to agree with you, but at least you likely will be understood in the rest of your treatise. Some of us have taken it for granted that readers would automatically agree with the observation that the ability of two animals bred together to produce fertile offspring is proof that they are of the same “kind.”
Let’s try to agree here on meanings or the terms I use. First, remember that “canid” means “dog-like” and is normally not capitalized. “Canis” or “canine” for practical purposes are almost interchangeable and mean “dog/wolf family member.” When Canis is used in the scientific name, it is capitalized, but the sub-types (lupus, familiaris, dingo, etc.) are not capitalized when part of that same name: Normally, members of a Canis sub-group can interbreed and produce viable and fertile offspring (crosses or crossbreeds).
Most people will agree on what a breed of dog is, yet some registries recognize four separate “breeds” of what others maintain is one single “breed”. Examples: the Belgian Shepherd has a variety of colors and coat types. Most registries split the Norfolk and Norwich Terriers into two breeds due to ears being either up or folded over. There are many such examples in the annals of dog registries.
I call my dog consulting/judging/writing business “All Things Canine.” In my lexicon, I often use the words canine and dog interchangeably, except when drawing attention to the slight differences between members or “breeds” of the canine world. When I talk about a canine breed, I refer to a collection of individuals that have resemblance and relative inbreeding (common ancestors). The reason I say “relative” is that if you go far enough back in the recorded or hypothetical pedigree, you will find they all came from the same pair (those that walked off Noah’s ark, if you will).
For example: geographic isolation and environment created the differences that evolved between the Tibetan Mastiff, Saluki, Malamute, and Dingo. As trade routes and human migration expanded, more breeds and intermediate variations arose. Meanwhile, wild canines, mostly because of greater geographic isolation, evolved and crossed much less than their domesticated counterparts.
Thus we have slight differences in coat color variation between Arctic wolf, Malamute, sable German Shepherd Dog, and others that more resemble wolves and each other than do the phenotypically distant breeds. By the way, the effect of geographic isolation and limited travel still can be seen in the minor differences that have evolved between such similar breeds as Malinois, Tervuren, Laekenois, Groenendael, Briard, GSD, Beauceron, and Dutch Shepherd.
The English translations of the Bible use the word “kind” when stating that the animals were created in groups or types. It says that they reproduce “after their own kind,” meaning that monkeys and men do not have offspring together, nor do hyenas and harriers. One of the reasons that different “kinds” (we most often use the word “species”) are incompatible is that they have different numbers of chromosomes and thus greatly different numbers and types of genes. Rather like crossing a boat with a car and expecting it to run down the highway.
Wolf, Dingo, Coyote, Golden Jackal, Ethiopian Wolf, and domestic dog are estimated to have diverged around 3 to 4 million years ago. All of these canids have 78 chromosomes (some reports make the Golden Jackal an exception) and thus are able to “cross” and produce fertile offspring. Some people call that hybridizing, and others of us reserve the term hybrid for animals that cannot reproduce themselves in next-generation matings.
In the next paragraphs you will see two or three Latin words naming and categorizing the animal. The first part is the generic name, the genus of the animal. The second part is either called the specific name or species. Many scientists believe that other members of the greater “dog-like family” diverged 7 to 10 million years ago. Whatever the cause, they are less closely related and cannot hybridize with the wolf-like canids/canines. For example, the red fox has 38 chromosomes, the raccoon “dog” has 42 chromosomes, and the Fennec fox has 64 chromosomes, and therefore cannot crossbreed and produce offspring. Nor can the South American canids or the bat-eared foxes. It appears that any extra chromosomes (left over, unpaired during sex-cell division) are a lethal situation.
A puzzle seems to be that the Yellow or Golden Jackal (Canis aureus) has 74 chromosomes, yet produces offspring when mating with 78-chromosome canids.
Incidentally, although the African Wild “Dog” (Lycaon pictus) also has 78 chromosomes, it is entirely separate from the Wolf/Canis group and existed well before the evolution (diversification) of our tame companions. It is therefore considered distinct enough to be placed in its own genus.
As new analysis methods improve, the taxonomy of various species may be tossed from one genus to another. So it’s a good idea to check on Canidae family data periodically if you’d like to keep up with changes. For example, the Ethiopian Wolf or Simien jackal (Canis simensis), once thought to be in a different genus, is a true member of the dog/wolf community.
Scientific names often were applied to an animal before anyone knew of its ability to cross-breed, or what its chromosome number was. Most animals historically classified in the genus Canis can interbreed to produce fertile offspring, with apparently a couple of exceptions: the side-striped jackal, Canis adustus and black-backed jackal, Canis mesomelas. Mitochondrial DNA analyses display a large sequence divergence in black-backed jackals even from other jackal species. Although these latter two jackals theoretically could interbreed with each other to produce fertile offspring, it appears they cannot hybridize successfully with the rest of the genus Canis. Perhaps it would be less confusing to the lay public and the student if they were not called “Canis.” Scientists often reclassify and rename for the sake of greater accuracy, but sometimes this process is extremely slow and inefficient.
I live in a sparsely-settled area of Alabama near the Tennessee River and in the first years we were here, we had a neighbor about a mile away who made his living trapping and fishing. He sold pelts to furriers by mail. In the first years, the red wolf was often-enough found in his leg-traps, even though the field guides erroneously claimed that they were extinct except for a small part of Texas near the Mexican border. Now, I believe they are truly gone from this area, having been replaced by coyotes and civilization. (One report had it that about 250 red wolves remained in the U.S. but I’ll not take that as a reliable count.) As a scientist, I diligently examined my neighbor’s animals before and after skinning, and carefully observed differences in them both alive and not.
Many of the sites you will find in computer-Internet searches are erroneous. One of the better ones is: http://www.naturalworlds.org/wolf/moretopics/canid_list.asp Even there, you must be careful because while it lists many Canidae (plural of “canid”), readers might not realize that this is the Family name that includes more than one Genus. Subdivisions of the genus “Canis” (not quite the same as “canid”) create even more confusion because most listings, such as the following, neglect to tell you that some of them can interbreed, some can’t.
You may also see variants on spelling, and may come across distinctions such as “Family Canidae,” “Subfamily Caninae,” and “Tribe Canini.” Don’t worry about these; this is just another way to classify wolves and dogs that are fully capable of producing fertile mixed-“tribe” offspring.
Here is an example of how biologists categorize living creatures. Remember that at each indentation, I am giving only one example (in parentheses); you can go off on any number of other branches, the number of choices increasing as you go down the list.
Family (Canidae or Canids)
Species (C. lupus, C. familiaris, C. rufus, C. latrans)
Breeds (artificial, environment-caused, or man-made differences)
The exact definition of the last couple of categories is quite “fuzzy.” Some scientists commonly add here a discussion of varieties, sub-varieties, clades, and sub-species. Breeders may want to add Linebreeding (bloodlines). The whole attempt at building such trees or chains is based on similarities such as physical attributes and similarity of DNA sequences, where available.
Again, allow me to caution you to define your terms because they may have different meanings for different people.
List Of Canidae Species
Additional references : Foxes, Wolves, Jackals, and Dogs (1990)
Canines: (78 chromosomes in the first six listed)
Domestic dog - Canis familiaris or Canis lupus familiaris
Gray (Grey) Wolf - Canis lupus lupus (North America, Greenland, Europe, Asia)
Dingo - Canis familiaris dingo; (Australia, Asia)
Coyote - Canis latrans (North America)
Red Wolf - Canis rufus (North America) Some claim it is descended from grey wolf & coyote.
Simien Jackal - Canis simensis (Africa)
Golden (or Yellow) Jackal - Canis aureus; 74 chromosomes (Africa, Europe, Asia)
Side-Striped Jackal - Canis adustus (Africa) Probably would be better if not called “Canis.”
Black-Backed Jackal - Canis mesomelas (Africa) Probably would be better if not called “Canis.”
Dhole - Cuon alpinus (Asia)
Maned Wolf - Chrysocyon brachyurus (South America)
African Wild Dog - Lycaon pictus (Africa)
Red Fox - Red Fox - Vulpes vulpes (North America, Europe, Asia, Australia, North Africa)
Swift (Kit) Fox- Vulpes velox (North America)
Fennec Fox - Vulpes zerda or Fennecus zerda (North Africa)
Bengal Fox - Vulpes bengalensis (Asia)
Blanford’s Fox - Vulpes cana (West and South Asia)
Cape Fox - Vulpes chama (Africa)
Corsac Fox - Vulpes corsac (Asia)
Tibetan Fox - Vulpes ferrilata (Asia)
Pale Fox - Vulpes pallida (North Africa)
Ruppell’s Fox- Vulpes ruppelli (North Africa)
Gray (Grey) Fox - Urocyon cinereoargenteus (North America)
Island Gray (Grey) Fox - Urocyon littoralis (Islands of Santa Catalina, San Clemente, etc. off California coast)
Arctic Fox - Alopex lagopus (North America, Greenland, Europe, Asia)
Bat-Eared Fox - Otocyon megalotis (Africa)
Culpeo - Pseudoalopex culpaeus or Dusicyon culpaeus (South America)
Azara’s Zorro - Pseudalopex gymnocercus or Dusicyon gymnocercus (South America)
Sechuran Zorro - Pseudalopex sechurae or Dusicyon sechurae (South America)
Hoary Zorro - Pseudalopex vetulus or Dusicyon vetulus (South America)
Gray (Grey) Zorro - Pseudalopex griseous or Dusicyon griseous (South America)
Small Eared Zorro - Atelocynus microtis or Dusicyon microtis (South America)
Crab-Eating Zorro - Cerdocyon thous (South America)
Raccoon Dog - Nyctereutes procynoides (Europe, Asia)
Bush Dog - Speothos venaticus (South America)
The Book, Canids (2004) includes these that are now considered extinct:
Falkland Island Fox - Dusicyon australis (Falkland Islands)
Darwin’s Fox - Pseudalopex fulvipes (South America)
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