Diversity and the UC Davis Diversity Test

 What is diversity and why do we care?

— by Rebekah Zurbrugg

Dozens of studies have been done on small populations both in the wild and in captivity to demonstrate the effect of loss of diversity on those populations.  Reproduction and health decline as the diversity of a population is lost, and eventually extinction occurs. Over 100 domestic species have gone extinct between 2000-2014.

How does this apply to dog breeds?   As a species, canines have a lot of genetic diversity.  However, we segregate our species by breed. Each breed in general has large numbers, but we also often apply selection pressures to (make breeding choices for) them that result in the loss of genetic diversity.  These pressures include popular sires, world wars, selection for type etc. As a breed’s diversity declines and more and more of the population becomes closely related, breed specific diseases tend to increase and eventually become fixed within the population.  Some of these populations reach critical levels of ill health, and an outcross to another breed must be done to continue the population.

So when we talk about diversity in dogs, what are we talking about?  In general when people talk about diversity, they are talking about two aspects: diversity within a single dog and diversity within the breed itself.

When we talk about diversity within the dog, we are assessing how much of the genetic material they inherited from their sire is exactly the same as the genetic material they inherited from their dam.  When a dog inherits too many of the same genes from both parents, we call them inbred. It’s well known that inbreeding can cause many issues in populations and therefore it is encouraged to breed for heterozygous, or outbred, dogs while selecting for type, temperament, health etc.  Another issue of inbred dogs would be that they are more likely to express any recessive diseases they may carry for, for which we cannot test.

What does diversity at the breedwide level mean?  Diversity in the breed means that the breed as a whole has lots of different genes.  The genes can be so simple as coat color, to as complicated as the immune system or cardiac structure.  When the genes begin to be depleted, often genes that code for illness then become more frequent. When this happens, those genetic flaws will be expressed more often.

All dogs will have some mutation in its genome.  The reason genetic diversity is desirable is that it dilutes the risk of disease by having more genetics in the population and in individual dogs.  As dogs become closer in genetics, the greater that risk is of expressing disease.

How does this apply to the Poodle breed?

Poodles are one breed, divided into three varieties in the United States.  The Standard Poodle variety suffered an intense and prolonged bottleneck in the mid century (read more here http://standardpoodleproject.com/).  Over time, the majority of Standard Poodles have become as related as half siblings (https://cgejournal.biomedcentral.com/articles/10.1186/s40575-015-0026-5).  Due to the bottleneck, several difficult and complex diseases seem to be fixed (or able to be produced by the majority of standard poodles) or on the rise within the variety, including sebaceous adenitis, Addison’s disease, IMTP/AIHA and more.  However, diversity within the variety does remain and needs redistributed in the population. This can be achieved both by breeding for less inbred litters and to distribute less common genetics throughout the variety.

Miniature poodles have been found to be in a much better situation as a variety, with great depth and breadth of genetic diversity.  As a variety, they appear to enjoy much more diversity and, as a result, health. Inbreeding seems to occur in families, but when a breeder runs in to health issues, there are plenty of other lines and diversity within the population to breed to.  They can focus solely on breeding for less inbred litters (while selecting for type, temperament, health etc), with less emphasis on variety-wide diversity, as long as popular sires remain less common.

Toy poodles are currently being analyzed at UC Davis Veterinary Genetics laboratory through funding provided by the Poodle Club of America Foundation.  It is predicted that the variety will be very similar to Miniature poodles in diversity.

Where do you get the testing done?

Individual testing can be purchased at the UC Davis Veterinary Genetics Laboratory here: https://www.vgl.ucdavis.edu/services/dog/CanineGeneticDiversity.php

All three varieties can use tools and predictive software to see how related potential mates are and for litter outcomes using the UC Davis VGL canine diversity testing data on www.betterbred.com. The tools will predict how inbred a litter will be, as well as how typical or atypical the puppies (and sire and dam) will be in reference to the tested population. 

If you have questions, there are facebook groups available to learn more:

Standard poodles: https://www.facebook.com/groups/434529336729485/

Miniature Poodles: https://www.facebook.com/groups/1958888467766761/

Toy Poodles: https://www.facebook.com/groups/1982058578676945/