Hedrick P W, Miller P S
Department of Zoology, Arizona State University, Tempe 85287.
EXS. 1994;68:187-204. doi: 10.1007/978-3-0348-8510-2_16.
In recent years, more detailed genetic information has become available for individuals of endangered species in captive breeding programs. There have been suggestions that this information be used to identify rare alleles, particularly those at the MHC, that can be subsequently selected for captive breeding programs. First, we summarize the current information on the MHC relevant to conservation genetics, so that such a possible breeding program is seen in a proper perspective. For example, very few specific alleles at the MHC have been identified as selectively advantageous, even though there has been substantial effort to find such alleles in humans and a few other organisms. Further, many of the balancing selection models suggested for MHC variation are based on heterozygotes in general having a higher fitness than homozygotes and not on specific selectively advantageous alleles. Because there is no detailed data on MHC variability in captive populations, we used transferrin data in Przewalski's horses to evaluate a breeding program to select for rare alleles. In this species, one individual, 1060, has been identified to have the transferrin allele J. We determine the effect on founder contribution of multiply mating 1060 to increase the number of copies of this allele. Since there were 485 individuals in the population at this time, this extra mating had little detrimental effect on the distribution of founder contributions and the number of founder equivalents. We then selected 65, an ancestor of 1060, which had a high likelihood of being the individual that passed on the J allele in the lineage of 1060. We examined the effect of increasing the number of copies of alleles of 65 at a time when the population had only 22 other individuals. In this case, even though the founder contributions were changed more, there was also little effect on the founder contributions and the number of founder equivalents. Overall, it appears that selection that results in a limited change in the number of copies of rare alleles may not always have an overall detrimental effect. However, because other pedigrees may have very different properties, it is essential to perform a detailed pedigree analysis of any such selective breeding program to determine its effect before such a selection program is implemented.
近年来，在圈养繁殖计划中，濒危物种个体可获得更详细的基因信息。有人建议利用这些信息来识别稀有等位基因，尤其是主要组织相容性复合体（MHC）上的那些等位基因，随后可将其用于圈养繁殖计划的选择。首先，我们总结了目前与保护遗传学相关的MHC信息，以便能从正确的角度看待这样一个可能的繁殖计划。例如，尽管在人类和其他一些生物体中已付出大量努力寻找此类等位基因，但在MHC上被确定为具有选择优势的特定等位基因却非常少。此外，许多针对MHC变异提出的平衡选择模型是基于杂合子通常比纯合子具有更高的适应性，而不是基于特定的具有选择优势的等位基因。由于没有关于圈养种群中MHC变异性的详细数据，我们使用普氏野马的转铁蛋白数据来评估一个选择稀有等位基因的繁殖计划。在这个物种中，已确定个体1060拥有转铁蛋白等位基因J。我们确定让1060多次交配以增加该等位基因拷贝数对奠基者贡献的影响。由于此时种群中有485个个体，这种额外的交配对奠基者贡献的分布和有效奠基者数量几乎没有不利影响。然后我们选择了65，它是1060的一个祖先，极有可能是在1060的谱系中传递J等位基因的个体。我们研究了在种群中仅有另外22个个体时增加65等位基因拷贝数的影响。在这种情况下，尽管奠基者贡献的变化更大，但对奠基者贡献和有效奠基者数量的影响仍然很小。总体而言，似乎导致稀有等位基因拷贝数有限变化的选择可能并不总是会产生整体不利影响。然而，由于其他谱系可能具有非常不同的特性，在实施任何此类选择育种计划之前，对其进行详细的谱系分析以确定其效果至关重要。
