Moss Landing Marine Laboratories, CA 95039, USA.
Mol Ecol. 2009 Dec;18(24):5074-85. doi: 10.1111/j.1365-294X.2009.04416.x. Epub 2009 Nov 13.
Genetic assignment methods provide an appealing approach for characterizing dispersal patterns on ecological time scales, but require sufficient genetic differentiation to accurately identify migrants and a large enough sample size of migrants to, for example, compare dispersal between sexes or age classes. We demonstrate that assignment methods can be rigorously used to characterize dispersal patterns in a marbled murrelet (Brachyramphus marmoratus) population from central California that numbers approximately 600 individuals and is only moderately differentiated (F(ST) approximately 0.03) from larger populations to the north. We used coalescent simulations to select a significance level that resulted in a low and approximately equal expected number of type I and II errors and then used this significance level to identify a population of origin for 589 individuals genotyped at 13 microsatellite loci. The proportion of migrants in central California was greatest during winter when 83% of individuals were classified as migrants compared to lower proportions during the breeding (6%) and post-breeding (8%) seasons. Dispersal was also biased toward young and female individuals, as is typical in birds. Migrants were rarely members of parent-offspring pairs, suggesting that they contributed few young to the central California population. A greater number of migrants than expected under equilibrium conditions, a lack of individuals with mixed ancestry, and a small number of potential source populations (two), likely allowed us to use assignment methods to rigorously characterize dispersal patterns for a population that was larger and less differentiated than typically thought required for the identification of migrants.
遗传分配方法为在生态时间尺度上描述扩散模式提供了一种有吸引力的方法，但需要足够的遗传分化来准确识别移民，并且需要足够大的移民样本量，例如，比较性别或年龄类别的扩散。我们证明，分配方法可以严格用于描述加利福尼亚中部约 600 只个体的大理石斑海雀（Brachyramphus marmoratus）种群的扩散模式，该种群与北部较大的种群仅适度分化（F（ST）约为 0.03）。我们使用合并模拟选择一个显著水平，该水平导致 I 型和 II 型错误的预期数量低且大致相等，然后使用该显著水平来确定在 13 个微卫星基因座上进行基因分型的 589 个个体的起源种群。在冬季，当 83％的个体被归类为移民时，加利福尼亚中部的移民比例最高，而在繁殖（6％）和繁殖后（8％）季节的比例较低。扩散也偏向于年轻和雌性个体，这在鸟类中很常见。很少有移民是亲代 - 后代对的成员，这表明它们对加利福尼亚中部的种群贡献很少。在平衡条件下，移民的数量比预期的要多，混合血统的个体数量较少，潜在的来源种群数量较少（两个），这可能使我们能够使用分配方法来严格描述一个比通常认为需要识别移民的种群更大且分化程度更低的种群的扩散模式。
