Nomura Tetsuro
Department of Industrial Life Sciences, Faculty of Life Sciences, Kyoto Sangyo University, Kyoto 603-8555, Japan.
Animals (Basel). 2024 Jun 21;14(13):1844. doi: 10.3390/ani14131844.
Inbreeding is unavoidable in small populations. However, the deleterious effects of inbreeding on fitness-related traits (inbreeding depression) may not be an inevitable phenomenon, since deleterious recessive alleles causing inbreeding depression might be purged from populations through inbreeding and selection. Inbreeding purging has been of great interest in conservation biology and animal breeding, because populations manifesting lower inbreeding depression could be created even with a small number of breeding animals, if inbreeding purging exists. To date, many studies intending to detect inbreeding purging in captive and domesticated animal populations have been carried out using pedigree analysis. Ballou's ancestral inbreeding coefficient (FBAL-ANC) is one of the most widely used measurements to detect inbreeding purging, but the theoretical basis for FBAL-ANC has not been fully established. In most of the published works, estimates from stochastic simulation (gene-dropping simulation) have been used. In this report, the author provides a mathematical basis for FBAL-ANC and proposes a new estimate by hybridizing stochastic and deterministic computation processes. A stochastic simulation suggests that the proposed method could considerably reduce the variance of estimates, compared to ordinary gene-dropping simulation, in which whole gene transmissions in a pedigree are stochastically determined. The favorable property of the proposed method results from the bypass of a part of the stochastic process in the ordinary gene-dropping simulation. Using the proposed method, the reliability of the estimates of FBAL-ANC could be remarkably enhanced. The relationship between FBAL-ANC and other pedigree-based parameters is also discussed.
在小种群中，近亲繁殖是不可避免的。然而，近亲繁殖对与适应性相关性状的有害影响（近亲繁殖衰退）可能并非不可避免的现象，因为导致近亲繁殖衰退的有害隐性等位基因可能会通过近亲繁殖和选择从种群中清除。近亲繁殖清除在保护生物学和动物育种中备受关注，因为如果存在近亲繁殖清除现象，即使只有少量繁殖动物，也有可能培育出近亲繁殖衰退程度较低的种群。迄今为止，许多旨在检测圈养和家养动物种群中近亲繁殖清除现象的研究都采用了系谱分析。巴卢的祖先近亲繁殖系数（FBAL-ANC）是检测近亲繁殖清除最常用的指标之一，但其理论基础尚未完全确立。在大多数已发表的研究中，采用的是随机模拟（基因滴度模拟）的估计值。在本报告中，作者为FBAL-ANC提供了数学基础，并通过结合随机和确定性计算过程提出了一种新的估计方法。随机模拟表明，与普通基因滴度模拟相比，该方法能显著降低估计值的方差，在普通基因滴度模拟中，系谱中的全基因传递是随机确定的。该方法的良好特性源于绕过了普通基因滴度模拟中部分随机过程。使用该方法，FBAL-ANC估计值的可靠性可显著提高。同时还讨论了FBAL-ANC与其他基于系谱的参数之间的关系。
