Population analysis of the Fox Terrier (Wire) breed Genetic analysis of the Kennel Club pedigree records of the UK Fox Terrier (Wire) 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 Fox Terrier (Wire) 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: Fox Terrier (Wire) Figure 1: Number of registrations by year of birth Trend of registrations over year of birth (1980-2014) = 0.54 per year (with a 95% confidence interval of -3.68 to 4.77). 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 188 146 79 22 2 1 2.38 2.69 79.26 55.32 32.98 22.34 1981 616 310 159 25 2 1 3.87 4.37 81.66 61.53 37.01 24.68 1982 658 292 152 35 3 1 4.33 5.17 83.43 62.31 38.15 26.14 1983 682 298 139 31 3 1 4.91 5.51 83.28 62.76 37.83 23.75 1984 779 316 133 45 3 1 5.86 7.36 85.11 63.41 39.15 27.6 1985 673 290 152 28 3 1 4.43 4.61 82.91 60.62 34.77 22.88 1986 651 277 129 43 3 2 5.05 5.99 84.18 61.75 37.48 23.96 1987 619 259 119 60 3 1 5.2 7.42 83.2 63.17 42.65 30.53 1988 648 240 127 31 3 1 5.1 5.51 82.41 61.11 37.04 22.22 1989 972 272 123 71 5 5 7.9 8.56 80.76 59.47 33.13 20.68 1990 839 226 115 31 6 6 7.3 5.75 78.19 52.92 28.25 16.81 1991 924 237 114 85 5 3 8.11 10.29 81.17 61.15 36.69 26.52 1992 728 181 92 59 5 5 7.91 8.61 80.63 61.4 34.34 23.08 1993 643 174 97 32 5 3 6.63 5.46 76.98 53.03 30.02 18.2 1994 687 185 101 44 5 5 6.8 7.35 79.18 58.81 36.39 23.14 1995 700 173 89 40 5 3 7.87 7.52 80.14 56.57 33.71 19.14 1996 607 161 90 31 5 4 6.74 5.75 78.58 54.04 29.49 20.1 1997 726 182 89 87 5 5 8.16 11.06 80.3 60.19 40.5 26.86 1998 632 171 87 34 5 4 7.26 7.11 80.85 57.44 33.86 20.73 1999 658 177 93 27 5 5 7.08 5.93 79.94 55.78 28.27 17.48 2000 628 167 80 94 5 1 7.85 12.24 83.92 66.24 43.95 32.01 2001 586 156 67 79 5 4 8.75 12.13 82.42 63.65 44.2 28.16 2002 692 176 75 41 5 5 9.23 8.18 81.65 57.95 30.92 18.06 2003 566 159 77 46 5 1 7.35 8.35 83.57 61.13 38.34 25.27 2004 793 209 97 78 5 1 8.18 10.07 82.6 61.03 38.97 25.09 2005 677 175 85 86 5 5 7.96 10.96 80.95 59.23 40.92 27.62 2006 658 173 87 35 5 1 7.56 7.3 82.22 58.36 34.04 19.45 2007 654 188 100 41 4 1 6.54 6.75 83.94 61.01 33.49 20.34 2008 795 208 114 29 4.5 4 6.97 6.32 80.63 59.5 30.31 18.87 2009 631 180 104 40 4.5 1 6.07 6.46 81.93 58.64 34.87 22.5 2010 664 180 110 28 4 1 6.04 5.8 80.57 59.49 34.19 21.08 2011 699 192 113 36 4 1 6.19 5.94 80.83 57.65 31.62 21.03 2012 618 164 100 34 5 1 6.18 6.01 81.23 58.25 33.01 20.71 2013 650 169 94 48 5 4 6.91 6.87 79.38 57.85 32.15 21.08 2014 612 150 83 30 5 4 7.37 5.86 76.63 51.96 28.59 16.83 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) = 3.61 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 = 42.1 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 584.6 712.6 764.2 664.6 653 683 648.6 Total #sires 377 373 282 254 228 278 286 Max #progeny 137 137 209 108 253 121 134 Mean #progeny 7.7374 9.5496 13.546 13.079 14.316 12.281 11.329 Median #progeny 3 4 7 8 6 6 6 Mode #progeny 1 1 4 5 4 1 1 SD #progeny 12.348 15.429 20.689 17.06 23.811 16.774 14.821 Skew #progeny 4.8484 4.3554 4.7045 3.1307 5.5449 2.901 3.6102 Total #dams 916 883 675 576 595 630 587 Max #progeny 17 26 29 24 27 24 26 Mean #progeny 3.1845 4.034 5.6593 5.7674 5.4857 5.419 5.5196 Median #progeny 2 3 5 5 5 4 5 Mode #progeny 1 1 4 4 4 1 1 SD #progeny 2.6051 3.1556 4.1567 4.129 3.9043 4.1031 3.971 Skew #progeny 1.8437 1.7592 1.9071 1.3865 1.3895 1.4791 1.2635 Rate of inbreeding 0.023995 0.01193 0.042592 0.001093 0.013224 0.021754 0.01685 Generation interval 3.4471 3.4062 3.5753 3.838 3.615 3.8388 3.52 Effective pop size 20.838 41.911 11.739 457.56 37.811 22.985 29.674 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
Comments The rate of inbreeding in this breed has remained relatively steady but high over the whole period. This implies genetic variation is steadily being lost from the population. There appears to be extensive use of popular dogs 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. 8