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EXPLANATION OF FIGURE 3 The 5 X 5 Di-Allele Breeding Matrix Over generations, genetic diversity can decline in captive populations. Controlled breeding using marked broodstock, paired matings, equal sex ratios, and equal numbers from pedigreed family lots can reduce loss of variation. 1. Ten unrelated parents, five males (columns) and five females (rows) are bred using a 5 X 5 matrix - the "di-allele" cross (Kapuscinski et al. 1993). 2. Effective population size is 10. 3. Figure 3 illustrates a single locus, multi-allelic (10 unique. allele) system. Each unique allele is represented in the figure with a different color. 4. Each parent in this illustration is limited to two alleles that are homozygous. 5. 25 heterozygous F lots or genotypes are produced by the matings, resulting in all possible genotypes. 6. The breeding matrix produces half-sib maternal (within rows) and half-sib paternal (within columns) F1 family lots. 7. Breeding within family lots (brother/sister or full-sib matings (i.e., mating an Al male with an Al female) results in inbreed- ing in the F2 generation. See lower left illustration in Fig. 3. Inbreeding results in an increased frequency of homozygous genotypes and a decreased frequency of heterozygous genotypes. This results in an increased frequency of familial alleles and a loss of population alleles, with a loss of fitness in offspring because of increasing deleterious recessive alleles. 8. Breeding within a row or column produces half-sib matings (i.e., mating an Al male with an A2 female), that also results in inbreeding, but not to the extent of brother/sister matings. Homozygosity increases at a reduced rate when compared to full-sib matings. See lower center illustration of Figure 3. 9. Mating progeny from outside columns and rows prevents inbreeding. All F family lots are heterozygous and genetic diversity is maintained. See lower right illustration in Figure 3. 24 C7 • •