Kardos Marty, Allendorf Fred W, Luikart Gordon
Division of Biological Sciences, University of Montana, Missoula, MT 59812, USA.
Mol Ecol Resour. 2014 May;14(3):519-30. doi: 10.1111/1755-0998.12193. Epub 2013 Dec 8.
Heterozygosity-fitness correlations (HFCs) have been observed for several decades, but their causes are often elusive. Tests for identity disequilibrium (ID, correlated heterozygosity between loci) are commonly used to determine if inbreeding depression is a possible cause of HFCs. We used computer simulations to determine how often ID is detected when HFCs are caused by inbreeding depression. We also used ID in conjunction with HFCs to estimate the proportion of variation (r(2)) in fitness explained by the individual inbreeding coefficient (F). ID was not detected in a large proportion of populations with statistically significant HFCs (sample size = 120 individuals) unless the variance of F was high (σ(2)(F) ≥ 0.005) or many loci were used (100 microsatellites or 1000 SNPs). For example, with 25 microsatellites, ID was not detected in 49% of populations when HFCs were caused by six lethal equivalents and σ(2)(F) was typical of vertebrate populations (σ(2)(F) ≈ 0.002). Estimates of r(2) between survival and F based on ID and HFCs were imprecise unless ID was strong and highly statistically significant (P ≈ 0.01). These results suggest that failing to detect ID in HFC studies should not be taken as evidence that inbreeding depression is absent. The number of markers necessary to simultaneously detect HFC and ID depends strongly on σ(2)(F). Thus the mating system and demography of populations, which influence σ(2) (F), should be considered when designing HFC studies. ID should be used in conjunction with HFCs to estimate the correlation between fitness and F, because HFCs alone reveal little about the strength of inbreeding depression.
几十年来人们一直在观察杂合性与适合度的相关性（HFCs），但其成因往往难以捉摸。同一性不平衡检验（ID，基因座间的相关杂合性）通常用于确定近亲繁殖衰退是否是HFCs的一个可能原因。我们使用计算机模拟来确定当HFCs由近亲繁殖衰退引起时，ID被检测到的频率。我们还将ID与HFCs结合起来，以估计个体近亲繁殖系数（F）所解释的适合度变异比例（r(2)）。在很大一部分具有统计学显著HFCs的群体（样本量 = 120个个体）中未检测到ID，除非F的方差很高（σ(2)(F) ≥ 0.005）或使用了许多基因座（100个微卫星或1000个单核苷酸多态性）。例如，使用25个微卫星时，当HFCs由六个致死当量引起且σ(2)(F)是脊椎动物群体的典型值（σ(2)(F) ≈ 0.002）时，49%的群体中未检测到ID。基于ID和HFCs对生存与F之间的r(2)估计并不精确，除非ID很强且具有高度统计学显著性（P ≈ 0.01）。这些结果表明，在HFC研究中未能检测到ID不应被视为不存在近亲繁殖衰退的证据。同时检测HFC和ID所需的标记数量在很大程度上取决于σ(2)(F)。因此，在设计HFC研究时应考虑影响σ(2)(F)的群体交配系统和种群统计学特征。ID应与HFCs结合使用以估计适合度与F之间的相关性，因为仅HFCs几乎无法揭示近亲繁殖衰退的强度。
