Population analysis of the Leonberger breed Genetic analysis of the Kennel Club pedigree records of the UK Leonberger population has been carried out with the aim of estimating the rate of loss of genetic diversity within the breed and providing information to guide a future sustainable breeding strategy. The population statistics summarised provide a picture of trends in census size, the number of animals used for breeding, the rate of inbreeding and the estimated effective population size. The rate of inbreeding and estimated effective population size indicate the rate at which genetic diversity is being lost within the breed. However, the number of animals of this breed registered with the Kennel Club per year has not been consistently high enough to allow all intended features of the report to be presented. Summary of results The analysis utilises the complete computerised pedigree records for the current UK Kennel Club registered Leonberger population, and statistics were calculated for the period 1980-2014. 1
Figure 1: a plot of number of registrations by year of birth, indicative of any changing trend in popularity of the breed. Breed: Leonberger Figure 1: Number of registrations by year of birth 2
Table 1: census statistics by year where available, including sire use statistics. Table 1: by year (1980-2014), the number of registered puppies born, by the number of unique dams and sires; maximum, median, mode, mean and standard deviation of number of puppies per sire; and the percentage of all puppies born to the most prolific 50%, 25%, 10% and 5% of sires. year #born #dams #sires puppies per sire %puppies sired by most prolific sires max median mode mean sd 50% sires 25% sires 10% sires 5% sires 1980 1 1 1 1 1 1 1 0 n/a n/a n/a n/a 1981 7 2 2 6 3.5 1 3.5 3.54 n/a n/a n/a n/a 1982 2 2 2 1 1 1 1 0 n/a n/a n/a n/a 1983 13 4 4 8 2 1 3.25 3.3 n/a n/a n/a n/a 1984 1 1 1 1 1 1 1 0 n/a n/a n/a n/a 1985 11 3 3 7 3 1 3.67 3.06 n/a n/a n/a n/a 1986 19 4 3 11 7 1 6.33 5.03 n/a n/a n/a n/a 1987 15 2 2 8 7.5 7 7.5 0.71 n/a n/a n/a n/a 1988 14 2 2 10 7 4 7 4.24 n/a n/a n/a n/a 1989 41 9 7 18 5 2 5.86 5.87 n/a n/a n/a n/a 1990 12 6 6 5 1 1 2 1.67 n/a n/a n/a n/a 1991 42 9 7 14 7 1 6 5.13 n/a n/a n/a n/a 1992 74 12 11 19 7 1 6.73 6.15 91.89 59.46 25.68 25.68 1993 80 15 12 24 3 1 6.67 8.41 91.25 72.5 30 30 1994 94 14 10 29 6.5 1 9.4 9.71 85.11 68.09 30.85 30.85 1995 143 26 17 27 6 1 8.41 8.02 84.62 57.34 35.66 18.88 1996 221 31 19 42 8 1 11.63 12.06 89.14 64.71 34.39 19 1997 215 34 21 56 8 1 10.24 13.2 87.91 62.33 42.79 26.05 1998 245 40 30 32 8 1 8.17 8.14 83.27 59.59 34.69 24.9 1999 298 44 26 42 8 7 11.46 10.85 78.19 58.72 37.92 14.09 2000 263 38 29 26 9 1 9.07 6.33 77.19 46.01 25.48 9.89 2001 296 46 32 56 9 9 9.25 9.58 76.35 50.34 30.41 25 2002 340 53 36 28 8 1 9.44 8.15 83.82 57.06 29.12 16.18 2003 317 46 35 26 9 9 9.06 6.32 76.97 49.84 27.13 14.83 2004 360 62 45 39 6 1 8 7.95 86.67 58.33 34.17 17.78 2005 364 60 43 36 7 1 8.47 8.69 87.09 60.16 32.69 18.68 2006 444 72 43 34 8 1 10.33 8.39 81.08 54.95 26.13 14.64 2007 375 58 41 33 7 1 9.15 7.64 81.6 52.8 28.27 15.73 2008 473 72 42 43 9 1 11.26 10.29 82.88 58.56 28.96 17.97 2009 284 52 36 27 7 1 7.89 7 83.1 55.99 32.04 17.96 2010 407 68 46 36 7 1 8.85 7.6 79.61 54.3 31.45 15.97 2011 350 60 41 50 5 1 8.54 10.53 89.14 63.14 39.14 26.29 2012 300 56 45 21 4 1 6.67 6.17 87.33 59 30.33 13 2013 385 69 49 38 5 1 7.86 9.27 88.83 64.42 41.56 18.96 2014 354 48 33 54 8 6 10.73 9.94 77.97 53.39 29.1 22.88 3
Generation interval: the mean average age (in years) of parents at the birth of offspring which themselves go on to reproduce. Mean generation interval (years) = 3.48 Estimated effective population size: the rate of inbreeding is used to estimate the effective population size of the breed. The effective population size is the number of breeding animals in an idealised, hypothetical population that would be expected to show the same rate of loss of genetic diversity (rate of inbreeding) as the breed in question. It may be thought of as the size of the gene pool of the breed. Below an effective population size of 100 (inbreeding rate of 0.50% per generation) the rate of loss of genetic diversity in a breed/population increases dramatically (Food & Agriculture Organisation of the United Nations, Monitoring animal genetic resources and criteria for prioritization of breeds, 1992). An effective population size of below 50 (inbreeding rate of 1.0% per generation) indicates the future of the breed many be considered to be at risk (Food & Agriculture Organisation of the United Nations, Breeding strategies for sustainable management of animal genetic resources, 2010). Where the rate of inbreeding is negative (implying increasing genetic diversity in the breed), effective population size is denoted n/a. Estimated effective population size = 759.4 NB - this estimate is made using the rate of inbreeding over the whole period 1980-2014 4
Table 2: a breakdown of census statistics, sire and dam usage and indicators of the rate of loss of genetic diversity over 5 year periods (1980-4, 1985-9, 1990-4, 1995-9, 2000-4, 2005-9, 2010-14). Rate of inbreeding and estimated effective population size for each 5-year block can be observed. Table 2: by 5-year blocks, the mean number of registrations; for sires the total number used, maximum, mean, median, mode, standard deviation and skewness (indicative of the size of the tail on the distribution) of number of progeny per sire; for dams the total number used, maximum, mean, median, mode, standard deviation and skewness of number of progeny per dam; rate of inbreeding per generation (as a decimal, multiply by 100 to obtain as a percentage); mean generation interval; and estimated effective population size. years 1980-1984 1985-1989 1990-1994 1995-1999 2000-2004 2005-2009 2010-2014 mean #registrations 4.8 20 60.4 224.4 315.2 388 359.2 Total #sires 8 10 32 79 110 136 144 Max #progeny 8 28 67 135 104 79 136 Mean #progeny 2.875 9.9 9.4063 14.19 14.318 14.257 12.465 Median #progeny 1 7.5 2 8 9 8 7 Mode #progeny 1 1 1 1 1 1 1 SD #progeny 2.949 8.7743 14.066 23.491 16.221 17.11 18.455 Skew #progeny 1.0233 0.79943 2.5224 3.1437 2.1276 1.7852 3.4122 Total #dams 8 15 49 126 188 236 231 Max #progeny 8 17 26 33 29 33 35 Mean #progeny 2.875 6.6 6.1429 8.881 8.3777 8.2161 7.7706 Median #progeny 1 6 5 8 8 8 6 Mode #progeny 1 1 1 1 1 1 1 SD #progeny 2.949 4.4689 6.069 6.9543 6.2446 6.2173 6.9797 Skew #progeny 1.0233 0.73602 1.5711 1.2749 0.99139 0.97344 1.4998 Rate of inbreeding 0.040864 0.042108-0.01412 0.006725 0.021882-0.02162-0.02054 Generation interval 1.537 3.9112 3.7088 3.4629 3.8063 3.6483 4.4563 Effective pop size 12.236 11.874 n/a 74.348 22.85 n/a n/a 5
Figure 3: a histogram ( tally distribution) of number of progeny per sire and dam over each of the seven 5-year blocks above. A longer tail on the distribution of progeny per sire is indicative of popular sires (few sires with a large number of offspring, known to be a major contributor to a high rate of inbreeding). Figure 3: Distribution of progeny per sire (blue) and per dam (red) over 5-year blocks (1980-4 top, 2010-14 bottom). Vertical axis is a logarithmic scale. 6
Comments As can be seen from figure 1, the number of animals of this breed registered with the Kennel Club has risen in recent years. This increase in numbers is likely to have been accomplished with use of migrant animals for breeding. The small initial population size and influence of migrant animals mean there may be large fluctuations in the rate of inbreeding and effective population size. There appears to be evidence of popular dogs used as sires in this breed (the 'tail' of the blue distribution in figure 3). It should be noted that, while animals imported from overseas may appear completely unrelated, this is not always the case. Often the pedigree available to the Kennel Club is limited in the number of generations, hampering the ability to detect true, albeit distant, relationships. 7