Population analysis of the Spaniel (English Springer) breed Genetic analysis of the Kennel Club pedigree records of the UK Spaniel (English Springer) 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. The analysis also calculates the average relationship (kinship) among all individuals of the breed born per year and is used to determine the level of inbreeding that might be expected if matings were made among randomly selected dogs from the population (the expected rate of inbreeding). Summary of results The analysis utilises the complete computerised pedigree records for the current UK Kennel Club registered Spaniel (English Springer) 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, followed by the yearly trend in number of animals registered (and 95% confidence interval). Breed: Spaniel (English Springer) Figure 1: Number of registrations by year of birth Trend of registrations over year of birth (1980-2014) = 260.98 per year (with a 95% confidence interval of 188.99 to 332.97). 2
Table 1: census statistics by year, 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 2612 1501 937 75 2 1 2.79 4.14 80.32 59.49 38.67 27.26 1981 5485 2004 1215 82 3 1 4.51 6.21 82.39 62.02 40.27 27.89 1982 6760 2142 1328 106 3 2 5.09 7.88 81.97 62.38 42.06 30.19 1983 6662 2156 1301 109 3 2 5.12 7.32 81.99 61.44 40.03 27.75 1984 6406 2095 1299 106 3 1 4.93 7.55 82.22 62.16 40.43 28.57 1985 6465 2000 1281 146 3 2 5.05 8.27 81.16 61.24 41.18 29.67 1986 6368 1966 1215 160 3 2 5.24 8.95 82.13 62.34 41.61 30.45 1987 5730 1745 1131 197 3 2 5.07 8.7 81.12 60.12 39.39 29.06 1988 5999 1708 1119 145 4 2 5.36 7.96 81.23 59.64 39.61 28.67 1989 10471 1895 1161 260 6 6 9.02 14.38 79.07 57.82 38.71 28.42 1990 10388 1798 1094 271 7 6 9.5 15.55 78.01 57.81 38.33 28.27 1991 9959 1704 1035 314 7 6 9.62 14.73 77.12 56.68 37.08 26.8 1992 10713 1818 1119 278 7 7 9.57 15.69 76.97 56.87 38.28 28.2 1993 10884 1818 1123 340 7 6 9.69 17.03 77.05 56.8 38.08 28.18 1994 11921 1981 1224 335 7 6 9.74 17.86 77.2 57.39 38.81 28.85 1995 12862 2115 1316 215 7 6 9.77 13.95 76.6 56.14 37.2 26.96 1996 14256 2349 1425 288 7 6 10 14.91 77.47 57.15 37.58 26.82 1997 14095 2316 1459 266 7 7 9.66 13.59 75.83 55.25 36.59 26.28 1998 12315 2028 1346 205 7 7 9.15 11.78 75.6 54.23 35.29 24.9 1999 12602 2028 1353 202 7 6 9.31 11.87 74.63 53.14 34.15 24.3 2000 11819 1955 1308 179 7 6 9.04 11.28 75.23 53.61 35.13 24.8 2001 11780 1955 1298 295 7 6 9.08 13.3 75.35 54.15 35.98 26.49 2002 12639 2105 1363 283 7 7 9.27 13.49 75.85 54.8 36.47 26.6 2003 13934 2258 1444 274 7 7 9.65 13.64 75.37 54.96 36.36 26.5 2004 14589 2339 1440 243 7 7 10.13 14.21 76.27 56.23 37.76 27.53 2005 15372 2481 1608 255 7 7 9.56 12.44 75.5 54.54 35.08 24.1 2006 15214 2429 1536 188 7 7 9.9 12.16 75.63 54.81 35.11 24.6 2007 14777 2368 1548 139 7 7 9.55 11.07 75.16 53.94 34.51 24.11 2008 14600 2316 1485 162 7 7 9.83 12.05 75.79 55.03 35.9 25.53 2009 12791 2045 1360 141 7 6 9.41 10.69 75.08 53.76 34.02 23.71 2010 13851 2224 1472 160 7 6 9.41 10.78 75.16 53.72 34.08 23.61 2011 12813 2086 1355 162 7 7 9.46 10.56 75.65 54.37 33.65 22.81 2012 12505 2002 1321 152 7 6 9.47 10.82 74.88 53.45 33.76 23.77 2013 11100 1779 1199 149 7 7 9.26 9.5 74.05 52.13 32.03 21.41 2014 10259 1643 1044 237 7 6 9.83 12.31 75.01 54.03 34.15 23.82 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) = 4.45 Figure 2: a plot of the annual mean observed inbreeding coefficient (showing loss of genetic diversity), and mean expected inbreeding coefficient (from random mating ) over the period 1980-2014. Expected inbreeding is staggered by the generation interval and, where >2000 animals are born in a single year, the 95% confidence interval is indicated. Figure 2: Annual mean observed and expected inbreeding coefficients 4
Estimated effective population size: the rate of inbreeding (slope or steepness of the observed inbreeding in Figure 2) 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 = 45.1 NB - this estimate is made using the rate of inbreeding over the whole period 1980-2014 5
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 compared with the trend in observed inbreeding in Figure 2. 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 5585 7006.6 10773 13226 12952 14551 12106 Total #sires 3942 3894 3741 4579 4520 4862 4171 Max #progeny 336 771 1310 1036 1011 670 515 Mean #progeny 7.0797 8.9964 14.398 14.442 14.327 14.964 14.51 Median #progeny 3 4 8 8 8 8 8 Mode #progeny 1 2 6 6 6 7 6 SD #progeny 16.396 23.44 40.652 32.448 32.699 29.783 25.465 Skew #progeny 10.773 16.204 19.874 15.151 14.676 10.602 8.9704 Total #dams 7715 7266 6915 8241 8024 8747 7522 Max #progeny 31 36 55 60 43 47 41 Mean #progeny 3.6174 4.8214 7.7893 8.0244 8.0708 8.3175 8.0461 Median #progeny 3 4 7 7 7 7 7 Mode #progeny 1 2 6 6 7 7 7 SD #progeny 3.0172 3.7935 5.1888 5.3193 5.1642 5.4293 4.9896 Skew #progeny 2.329 2.1406 2.0094 2.0602 1.7571 1.9029 1.6507 Rate of inbreeding 0.016775 0.009996 0.014283 0.014297 0.00777 0.009397 0.014666 Generation interval 3.9145 4.2962 4.5474 4.5178 4.6302 4.7306 4.5672 Effective pop size 29.807 50.02 35.006 34.971 64.353 53.207 34.092 6
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 very 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. 7
8 September 2015
Comments The rate of inbreeding in this breed has remained consistently steady and high over the whole period. This implies genetic variation is steadily being lost from the population. It appears that the extensive use of popular dogs as sires has eased a little (the tail of the blue distribution shortening 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. 9