Wild Type in Pigeons, Columba livia

WILD TYPE by Frank Mosca

Pure Scottish Rock Dove:Columba livia Photographer unknown. If you do know whose work this is, please let me know and I'll be happy to credit it.

Let's face it: people make the rules. You'll never find a group of star-nosed moles sitting around discussing the differences between one population of earthworms and another. Yet, scientists discuss differences in populations of various animals and plants all the time. But how can one rationally discuss differences between populations unless one has a standard, i.e., a base line group to compare these differences to? For our purposes, this base line group will be known as the "wild-type".

The ancestor to our domestic pigeons is the wild species known as the rock-dove, rock-pigeon, or common pigeon. Its scientific name is Columba livia. This species is a wide ranging one found from Scotland to Iran and from northern Europe to northern Africa. When we look at it, what we find overall is a fairly standard dove-gray bird weighing about 8 oz. (227 g.) with two black bars on its wings and a black sub-terminal tail bar. Yet, in its vast range there are some obvious differences in its various population. Some show red orbital skin around the eyes rather than the more common dark skin. Some have a dark rump rather than a light one. The shade of blue also varies with some populations being darker than others. Some groups have youngsters with dark feet in the nest, some with light. There are also some minor differences in voice and size. So how do we decide which group is the one we'll use as are base line? Simple, we pick one. In biology, the base line group is the one which is first formally identified and described. In the case of the common pigeon, this is that population of pigeons found in western Europe. Here the common pigeon tends to have orange-red eyes, light rump and a fairly light blue color. It is this bird which is considered to be the wild-type. For our purposes in pigeon genetics, this bird is the median against which everything is judged.

Any mutation, or change, from this wild-type is compared to it and described. For example, the wild type pigeon has no crest. At some point in time, there was a mutation which caused the feathers of the rear of the neck or head to grow reversed. This mutation was described and given a genetic symbol (cr). When I say it was described, I don't simply mean that someone said a crest is a group of feathers which stand up in the back of the head. Rather, I mean that someone performed breeding tests to check how crest is inherited. It was found that if a crested bird was paired to a wild type bird that all the resulting young were non-crested. These young, called the F₁ generation, paired brother and sister produced both crested and non-crested young. Further testing indicated that crest was inherited as a simple (autosomal) recessive condition.

In like manner, Ash-red, a mutation (change) from wild-type was described. In this case, the mutation was found to be dominant to the wild type and also found to be sex-linked in its inheritance. But notice, everything is referred back to the wild-type. To all intents and purposes when we test domestic pigeons for color or structural changes from the wild-type, the bird we consider to be the standard tester is the blue bar homer. For most, not all, testings, this is considered to be the closest we can get to actually using the wild pigeon. Wild type also is used to simply mean the wild type condition for the factor we are testing. For example, suppose I want to test a black pigeon to see whether it is homozygous (carries two genes) or heterozygous (carries only one gene) for Spread. I simply need as my mate for this bird any non-spread pigeon. I don't care whether it's check, bar, barless. I don't care whether it's brown, blue or Ash-red. I simply want a bird which is wild-type (non-spread) at that particular spot on the chromosome where the mutation for spread would normally be found.

The important thing to remember about wild type is simply that it's the standard against which we judge everything. The genetic symbol for wild-type is (+). That's because we have no idea what goes into making the wild pigeon what it is. ONLY when there is a mutation from the normal wild type can we test. Some spots on the pigeon's chromosome seem to be more prone to mutation than others -- or the effect caused by a mutation there is more easily observed by us. The spot (locus) on the sex-chromosome where there has been a mutation to Almond is one such place. Here there are multiple alleles known. There might well be other spots on other chromosomes where there are also mutiple alleles, maybe even many more than in the Almond group, but such alleles may simply code for differences in blood type or the production of different enzymes in the bird's body. Things like this would seldom, if ever, be observed by the average fancier - and might easily escape notice in a laboratory setting as well.

So, recapping quickly. Wild type is the original type and is the standard against which we compare any mutation. If a mutation needs only one copy of itself in the bird's body to show its effects, we call it a dominant mutation. If it needs two copies of itself to show its effect, we call it a recessive mutation. So, we can say crest is a recessive mutation (to wild-type is always understood.) In like manner, Indigo is a dominant mutation (to wild type, again understood.) Wild type is ALWAYS our base line.

(Information I received in personal conversation on Sept. 26, 1997, with both Drew Lobenstein and Leon Stephens indicates there is a dominant crest mutation found as part of the geneotype of Jacobins. I've asked both men to please write up their findings. If the information is indeed accurate, then whoever first formally describes the mutation and its effect will have the honor of choosing the symbol which will represent it.)

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