Leonberger history suggests that they should not be a genetically diverse breed. Although they were formed as a hodgepodge of large continental dogs a little over a century ago, two World Wars devastated their numbers and possible rescue outcrosses are mostly undocumented.
The breed is believed to be the creation of one man, Heinrich Essig, who was a dog dealer and traveling salesman; his claimed formula was Landseer Newfoundland x Saint Bernard, followed by more Saint Bernards and a Pyrenean Mountain Dog with the goal being a large white dog that was fashionable at the time. After Essig’s death in 1889 his nephew had the inspiration to promote the breed as a lion-like mascot for the town of Leonberg and established the final conformation of the dogs as having a lion-like rough coat with reddish-brown coloration, a black mask and black sable accents. Like most breeds, the origin mythology is poorly documented and stud books were not kept in earnest on the breed for several decades after its establishment.
As a German breed, the Leonberger was severely affected by both World Wars: only 5 known breeding dogs survived the first war and only 8 pedigreed dogs emerged from the second. Two severe bottlenecks like this are not conducive to preserve genetic diversity within a closed population.
That is why I was surprised to find that the 5 Leonbergers which were DNA tested as part of a study analyzing the genetic composition of Alaskan Sled Dogs showed that they had excess heterozyosity compared to Hardy-Weinberg equilibrium. Of 141 breeds tested over 96 genetic marker sites, there were only 9 purebred breeds found to be surplus heterozygous and most of those are only marginally so.
Note, this is not a measure of gross diversity in the breed, it’s a measure of which way the breed is being pushed genetically, either toward more conformity and homozygosity or toward more diversity and heterozygosity.
Genetic rescue requires a push toward heterozygosity before reaching a new equilibrium with the new alleles.
Here is the actual data represented in the chart. The purposely out-crossed hybrid sled dogs were found to be 20% more diverse than equilibrium and the Leonberger was second only to the Puli with over 10% excess heterozyosity.
|Sled Dog – Sprinter||-0.20197|
|Cardigan Welsh Corgi||-0.05649|
|Grand Basset Griffon Vendeen||-0.02908|
I’ve only found one documented outcross on the Leonberger books: In 1954 a Leonberger stud Arko von Leonberg with a COI of 20% was bred to a Newfoundland dam Grisette von Bruckberg and one female from that litter, Alma von Rossbach, would cement herself into the Leonberger gene pool.
More recently European kennel clubs have registered Leonbergers with full breeding rights certificates “titre initial” (as opposed to a 3 generation provisional appendix registration “registre initial”) which are given after a number of criteria are met; typically an evaluation against the breed standard or significant show success, health testing, and perhaps even temperament evaluations. These dogs are believed to be pure-blooded Leonbergers instead of hybrid dogs which would normally take 3 generations to be admitted into the gene pool with full breeding rights and purebred status in registries that allow new blood. Sometimes they come with full pedigree and while the kennel club would void the known pedigree and perhaps calculate the COI of offspring as 0%, it’s not clear that either the registre initial or titre initial schemes are a source of new Leonberger blood.
Another possible source of Leonberger diversity lies in the history of Germany and the East after the wars. The Leonberger isn’t just a dog of the West and so it existed on both sides of the Iron Curtain. It is unknown and undocumented what sorts of possible crosses came into the breed during the Cold War before the reunification of Germany and the resumption of normal trade across Europe.
The last and least verifiable source of unexpected diversity would be intentional and unintentional pedigree fraud or error. It’s possible that some breeders when faced with a line that was not producing what they wanted or suffering from inbred disease or infertility decided to outcross, or an accidental litter proved sufficiently virtuous to register and the breeder either could not or did not choose to disclose this.
There’s also the possibility that I simply haven’t accounted for some factors which would have preserved heterozygosity in Leonbergers and that the bottlenecks did not have the expected effects on the gene pool. Certainly more questions than answers, but what an intriguing mystery it is.
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