Department of Animal Science, Faculty of Agriculture, University of Zagreb, Zagreb, Croatia.
Institute of Methodology, Faculty of Economic Science, Kaposvár University, Kaposvár, Hungary.
Genet Sel Evol. 2020 Jul 8;52(1):39. doi: 10.1186/s12711-020-00557-3.
Accumulation of detrimental mutations in small populations leads to inbreeding depression of fitness traits and a higher frequency of genetic defects, thus increasing risk of extinction. Our objective was to quantify the magnitude of inbreeding depression for survival at birth, in a closed rabbit population under long-term selection.
We used an information theory-based approach and multi-model inference to estimate inbreeding depression and its purging with respect to the trait 'kit survival at birth' over a 25-year period in a closed population of Pannon White rabbits, by analysing 22,718 kindling records. Generalised linear mixed models based on the logit link function were applied, which take polygenic random effects into account.
Our results indicated that inbreeding depression occurred during the period 1992-1997, based on significant estimates of the z-standardised classical inbreeding coefficient z.F (CI - 0.12 to - 0.03) and of the new inbreeding coefficient of the litter z.F (CI - 0.13 to - 0.04) as well as a 59.2% reduction in contributing founders. Inbreeding depression disappeared during the periods 1997-2007 and 2007-2017. For the period 1992-1997, the best model resulted in a significantly negative standardised estimate of the new inbreeding coefficient of the litter and a significantly positive standardised estimate of Kalinowski's ancestral inbreeding coefficient of the litter (CI 0.01 to 0.17), which indicated purging of detrimental load. Kindling season and parity had effects on survival at birth that differed across the three periods of 1992-1997, 1997-2007 and 2007-2017.
Our results support the existence of inbreeding depression and its purging with respect to kit survival at birth in this Pannon White rabbit population. However, we were unable to exclude possible confounding from the effects of parity and potentially other environmental factors during the study period, thus our results need to be extended and confirmed in other populations.
小种群中有害突变的积累会导致适合度性状的近交衰退和遗传缺陷的频率增加，从而增加灭绝的风险。我们的目标是量化在长期选择下的封闭兔群中，出生时的生存这一性状的近交衰退的幅度。
我们使用基于信息理论的方法和多模型推断，通过分析 22718 次分娩记录，估计了一个封闭的 Pannon White 兔群在 25 年期间，与“出生时幼崽存活”性状相关的近交衰退及其净化程度。应用基于对数几率函数的广义线性混合模型，该模型考虑了多基因随机效应。
我们的结果表明，1992-1997 年期间发生了近交衰退，这是基于 z 标准化经典近交系数 z.F（CI-0.12 到-0.03）和 litter z.F 的新近交系数（CI-0.13 到-0.04）的显著估计以及贡献创始人减少了 59.2%得出的。1997-2007 年和 2007-2017 年期间，近交衰退消失了。对于 1992-1997 年期间，最佳模型导致 litter 的新近交系数的标准化估计显著为负，而 litter 的 Kalinowski 祖先近交系数的标准化估计显著为正（CI0.01 到 0.17），这表明有害负荷的净化。分娩季节和胎次对出生时的存活率有影响，但在 1992-1997 年、1997-2007 年和 2007-2017 年这三个时期有所不同。
我们的研究结果支持在这个 Pannon White 兔群中，出生时幼崽存活这一性状存在近交衰退及其净化。然而，我们无法排除在研究期间胎次和潜在其他环境因素的影响，因此我们的结果需要在其他种群中扩展和验证。
