Heterozygosity of the Yellowstone wolves.
Heterozygosity of the Yellowstone wolves.
复制标题
黄石狼的杂合性。
DOI：
10.1111/j.1365-294x.2010.04746.x
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发表时间：
2010
影响因子：
4.9
通讯作者：
Rosenberg,NoahA
中科院分区：
文献类型：
--
作者：
Jankovic,Ivana;vonHoldt,BridgettM;Rosenberg,NoahA
在最近的一项研究中，vonHoldt等人（2008）调查了黄石国家公园灰狼（Canis lupus）重新引入计划在保护种群遗传变异方面的成功。他们评估了狼种群遗传多样性的各个方面，这些狼起源于1995年和1996年引入的41位创始人，并且自重新引入以来一直保持遗传隔离。vonHoldt等人（2008）在1995-2004年的初始恢复期取样了大量个体，对每个个体进行了26个微卫星位点的基因分型。他们的分析包括平均观察杂合度和预期杂合度（分别为HO和HE）的估计，总体上表明，这种孤立的狼种群在避免近亲繁殖和维持遗传多样性方面是有效的。然而，他们的遗传变异分析的某些方面似乎有些不相容。使用Nei（1987）杂合度估计器（ĤE）计算的期望杂合度水平表明，自1997年引种完成后，遗传变异呈下降趋势（图1A）。作者认为，如果这种趋势继续下去，狼的适应性可能会因为近亲繁殖和适应性降低的负面影响而下降。奇怪的是，报道的ĤO显示了与ĤE相反的趋势（图1A），表明杂合子个体的比例增加，可能表明随着时间的推移近亲繁殖减少。然而，ĤO始终低于ĤE，这一结果可能暗示了近亲繁殖。在十年的研究中，行为观察记录了很少的近亲繁殖案例（vonHoldt et al. 2008），很可能是近亲繁殖以外的因素导致了ĤE和ĤO之间的差异。vonHoldt et al.（2008）的黄石狼数据集异常丰富，因为所有采样个体的初始种群祖先规模较小，缺乏来自外部移民的基因流，交配等级和物种繁殖成功率的高差异，以及近乎全面的种群抽样（考虑到年度普查规模，每年抽样的种群比例高达~ 86%）。近交和相关样本中等位基因频率估计的最新进展（如Weir 1996； Broman 2001； Bourgain等人2004；DeGiorgio和Rosenberg 2009）表明，样本中近亲的存在引入了ĤE的向下偏倚，这可能解释了vonHoldt等人（2008）观察到的不寻常的杂合性。因此，我们感兴趣的是确定ĤE中包含亲缘关系引起的偏差是否会影响vonHoldt等人（2008）关于狼遗传变异时间趋势的结论。
In a recent study, vonHoldt et al.(2008) examined the success of the grey wolf (Canis lupus) reintroduction program into Yellowstone National Park in preserving the genetic variation of the population. They evaluated a variety of aspects of genetic diversity in the wolf population, which originated from 41 founders introduced in 1995 and 1996, and which has remained genetically isolated since the reintroduction. In each of a large number of individuals sampled during the initial recovery period, 1995–2004, vonHoldt et al.(2008) genotyped 26 microsatellite loci. Their analyses, which included estimates of mean observed and expected heterozygosity (HO and HE, respectively), generally indicated that this isolated wolf population is effective at inbreeding avoidance and maintenance of genetic diversity. However, some aspects of their genetic variation analyses appeared to be somewhat incompatible. Levels of expected heterozygosity, calculated using Nei’s (1987) heterozygosity estimator (ĤE), identified a decreasing trend in genetic variation starting from 1997, after the introductions were complete (Figure 1A). The authors suggested that if this trend continues, wolf fitness might decrease due to the negative effects of inbreeding and reduced adaptability. Curiously, the reported ĤO showed the opposite trend to ĤE (Figure 1A), demonstrating increasing proportions of heterozygous individuals, potentially indicative of a reduction in inbreeding over time. ĤO was consistently lower than ĤE, however, a result that might be suggestive of inbreeding. As behavioral observations documented very few cases of inbreeding over the ten years of the study (vonHoldt et al. 2008), it is likely that factors other than inbreeding have contributed to the discrepancy between ĤE and ĤO.The Yellowstone wolf dataset of vonHoldt et al.(2008) was unusually enriched for close relatives, due to the small size of the founding population ancestral to all sampled individuals, the lack of gene flow from outside immigrants, the mating hierarchy and high variance of reproductive success in the species, and the near-comprehensive sampling of the population (considering annual census sizes, the per-year proportion of the population sampled was as high as~ 86%). Recent developments in the estimation of allele frequencies from inbred and related samples (eg Weir 1996; Broman 2001; Bourgain et al. 2004; DeGiorgio & Rosenberg 2009) have demonstrated that the presence of close relatives in a sample introduces a downward bias in ĤE, providing a possible explanation for the unusual heterozygosity observations of vonHoldt et al.(2008). We were therefore interested in determining whether accounting for the bias in ĤE caused by the inclusion of relatives would affect the conclusions of vonHoldt et al.(2008) regarding temporal trends in wolf genetic variation.