Data from: Blood mercury levels of zebra finches are heritable: implications for the evolution of mercury resistance

Mercury is a ubiquitous metal contaminant that negatively impacts reproduction of wildlife and has many other sub-lethal effects. Songbirds are sensitive bioindicators of mercury toxicity and may suffer population declines as a result of mercury pollution. Current predictions of mercury accumulation and biomagnification often overlook possible genetic variation in mercury uptake and elimination within species and the potential for evolution in affected populations. We conducted a study of dietary mercury exposure in a model songbird species, maintaining a breeding population of zebra finches (Taeniopygia guttata) on standardized diets ranging from 0.0–2.4 μg/g methylmercury. We applied a quantitative genetics approach to examine patterns of variation and heritability of mercury accumulation within dietary treatments using a method of mixed effects modeling known as the 'animal model'. Significant variation in blood mercury accumulation existed within each treatment for birds exposed at the same dietary level; moreover, this variation was highly repeatable for individuals. We observed substantial genetic variation in blood mercury accumulation for birds exposed at intermediate dietary concentrations. Taken together, this is evidence that genetic variation for factors affecting blood mercury accumulation could be acted on by selection. If similar heritability for mercury accumulation exists in wild populations, selection could result in genetic differentiation for populations in contaminated locations, with possible consequences for mercury biomagnification in food webs.

汞（mercury）是一种广泛存在的金属污染物，会对野生动物的繁殖产生负面影响，同时还会引发诸多其他亚致死效应。鸣禽（songbirds）是汞毒性的敏感生物指示剂，可能因汞污染出现种群数量下降。当前针对汞富集与生物放大（biomagnification）的预测往往忽略了物种内个体在汞吸收与清除过程中可能存在的遗传变异，以及受影响种群的进化潜力。本研究以一种模式鸣禽物种为对象，探究其膳食汞暴露情况：我们维持了斑胸草雀（zebra finches，*Taeniopygia guttata*）的繁殖种群，为其提供浓度范围为0.0–2.4 μg/g的甲基汞（methylmercury）标准化日粮。我们采用定量遗传学（quantitative genetics）方法，并借助被称为“动物模型（animal model）”的混合效应建模手段，分析不同膳食处理组内汞富集的变异模式与遗传力。在同一膳食暴露水平的个体中，各处理组内的血液汞富集均存在显著变异；且该变异在个体间具有高度重复性。我们发现，处于中等膳食浓度暴露组的斑胸草雀，其血液汞富集存在显著的遗传变异。综合来看，上述结果表明，影响血液汞富集的相关因子的遗传变异可受到自然选择的作用。若野生种群中也存在类似的汞富集遗传力，则选择作用可能会导致污染区域的种群出现遗传分化，进而可能对食物网中的汞生物放大过程产生潜在影响。