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Assortative mating and fragmentation within dog breeds.

Björnerfeldt S, Hailer F, Nord M, Vilà C - BMC Evol. Biol. (2008)

Bottom Line: Pedigree analysis going three generations back in time confirmed that subgroups within poodles result from assortative mating imposed by breed standards as well as breeder preferences.The genetic structure observed in poodles is the result of local mating patterns, implying that breed fragmentation may be different in different countries.The same processes which have historically created dog breeds are still ongoing, and create further subdivision within current dog breeds.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Evolutionary Biology, Uppsala University, S-752 36 Uppsala, Sweden. Susanne.Bjornerfeldt@hgen.slu.se

ABSTRACT

Background: There are around 400 internationally recognized dog breeds in the world today, with a remarkable diversity in size, shape, color and behavior. Breeds are considered to be uniform groups with similar physical characteristics, shaped by selection rooted in human preferences. This has led to a large genetic difference between breeds and a large extent of linkage disequilibrium within breeds. These characteristics are important for association mapping of candidate genes for diseases and therefore make dogs ideal models for gene mapping of human disorders. However, genetic uniformity within breeds may not always be the case. We studied patterns of genetic diversity within 164 poodles and compared it to 133 dogs from eight other breeds.

Results: Our analyses revealed strong population structure within poodles, with differences among some poodle groups as pronounced as those among other well-recognized breeds. Pedigree analysis going three generations back in time confirmed that subgroups within poodles result from assortative mating imposed by breed standards as well as breeder preferences. Matings have not taken place at random or within traditionally identified size classes in poodles. Instead, a novel set of five poodle groups was identified, defined by combinations of size and color, which is not officially recognized by the kennel clubs. Patterns of genetic diversity in other breeds suggest that assortative mating leading to fragmentation may be a common feature within many dog breeds.

Conclusion: The genetic structure observed in poodles is the result of local mating patterns, implying that breed fragmentation may be different in different countries. Such pronounced structuring within dog breeds can increase the power of association mapping studies, but also represents a serious problem if ignored. In dog breeding, individuals are selected on the basis of morphology, behaviour, working or show purposes, as well as geographic population structure. The same processes which have historically created dog breeds are still ongoing, and create further subdivision within current dog breeds.

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Genetic similarity between poodle subgroups and eight other dog breeds. Neighbor-joining analysis of allelic composition at 27 microsatellite loci. Calculations are based on Nei's [25] standard genetic distances (DS), and numbers on branches correspond to bootstrap values from 1000 bootstrap resamplings across loci (only values above 50 are shown). Poodle 2, black and brown medium sized poodles; Poodle 3, black and brown miniature and toy poodles; Poodle 4, silver and white medium sized, miniature and toy poodles; Poodle 5, apricot medium sized, miniature and toy poodles.
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Figure 3: Genetic similarity between poodle subgroups and eight other dog breeds. Neighbor-joining analysis of allelic composition at 27 microsatellite loci. Calculations are based on Nei's [25] standard genetic distances (DS), and numbers on branches correspond to bootstrap values from 1000 bootstrap resamplings across loci (only values above 50 are shown). Poodle 2, black and brown medium sized poodles; Poodle 3, black and brown miniature and toy poodles; Poodle 4, silver and white medium sized, miniature and toy poodles; Poodle 5, apricot medium sized, miniature and toy poodles.

Mentions: These five groups of poodles were also genetically compared to 133 dogs from eight other breeds (Table 2). Standard poodles were as differentiated from smaller poodles as different breeds are from each other (pairwise FST = 0.150–0.517). For instance, the pairwise FST value between standard poodles and black and brown medium sized poodles was 0.265, larger than 40% of the comparisons between the five groups of poodles and the other 8 breeds included in this study. For example, the FST value between giant schnauzer and small white and silver poodles is just 0.170. A neighbor-joining analysis (Figure 3) based on another measure of genetic differentiation, Nei's [25] standard genetic distance (DS), shows standard poodles at the end of a long branch, indicating genetic uniqueness and separation from all other poodles.


Assortative mating and fragmentation within dog breeds.

Björnerfeldt S, Hailer F, Nord M, Vilà C - BMC Evol. Biol. (2008)

Genetic similarity between poodle subgroups and eight other dog breeds. Neighbor-joining analysis of allelic composition at 27 microsatellite loci. Calculations are based on Nei's [25] standard genetic distances (DS), and numbers on branches correspond to bootstrap values from 1000 bootstrap resamplings across loci (only values above 50 are shown). Poodle 2, black and brown medium sized poodles; Poodle 3, black and brown miniature and toy poodles; Poodle 4, silver and white medium sized, miniature and toy poodles; Poodle 5, apricot medium sized, miniature and toy poodles.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2266708&req=5

Figure 3: Genetic similarity between poodle subgroups and eight other dog breeds. Neighbor-joining analysis of allelic composition at 27 microsatellite loci. Calculations are based on Nei's [25] standard genetic distances (DS), and numbers on branches correspond to bootstrap values from 1000 bootstrap resamplings across loci (only values above 50 are shown). Poodle 2, black and brown medium sized poodles; Poodle 3, black and brown miniature and toy poodles; Poodle 4, silver and white medium sized, miniature and toy poodles; Poodle 5, apricot medium sized, miniature and toy poodles.
Mentions: These five groups of poodles were also genetically compared to 133 dogs from eight other breeds (Table 2). Standard poodles were as differentiated from smaller poodles as different breeds are from each other (pairwise FST = 0.150–0.517). For instance, the pairwise FST value between standard poodles and black and brown medium sized poodles was 0.265, larger than 40% of the comparisons between the five groups of poodles and the other 8 breeds included in this study. For example, the FST value between giant schnauzer and small white and silver poodles is just 0.170. A neighbor-joining analysis (Figure 3) based on another measure of genetic differentiation, Nei's [25] standard genetic distance (DS), shows standard poodles at the end of a long branch, indicating genetic uniqueness and separation from all other poodles.

Bottom Line: Pedigree analysis going three generations back in time confirmed that subgroups within poodles result from assortative mating imposed by breed standards as well as breeder preferences.The genetic structure observed in poodles is the result of local mating patterns, implying that breed fragmentation may be different in different countries.The same processes which have historically created dog breeds are still ongoing, and create further subdivision within current dog breeds.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Evolutionary Biology, Uppsala University, S-752 36 Uppsala, Sweden. Susanne.Bjornerfeldt@hgen.slu.se

ABSTRACT

Background: There are around 400 internationally recognized dog breeds in the world today, with a remarkable diversity in size, shape, color and behavior. Breeds are considered to be uniform groups with similar physical characteristics, shaped by selection rooted in human preferences. This has led to a large genetic difference between breeds and a large extent of linkage disequilibrium within breeds. These characteristics are important for association mapping of candidate genes for diseases and therefore make dogs ideal models for gene mapping of human disorders. However, genetic uniformity within breeds may not always be the case. We studied patterns of genetic diversity within 164 poodles and compared it to 133 dogs from eight other breeds.

Results: Our analyses revealed strong population structure within poodles, with differences among some poodle groups as pronounced as those among other well-recognized breeds. Pedigree analysis going three generations back in time confirmed that subgroups within poodles result from assortative mating imposed by breed standards as well as breeder preferences. Matings have not taken place at random or within traditionally identified size classes in poodles. Instead, a novel set of five poodle groups was identified, defined by combinations of size and color, which is not officially recognized by the kennel clubs. Patterns of genetic diversity in other breeds suggest that assortative mating leading to fragmentation may be a common feature within many dog breeds.

Conclusion: The genetic structure observed in poodles is the result of local mating patterns, implying that breed fragmentation may be different in different countries. Such pronounced structuring within dog breeds can increase the power of association mapping studies, but also represents a serious problem if ignored. In dog breeding, individuals are selected on the basis of morphology, behaviour, working or show purposes, as well as geographic population structure. The same processes which have historically created dog breeds are still ongoing, and create further subdivision within current dog breeds.

Show MeSH
Related in: MedlinePlus