Athrey N R Giridhar, Leberg Paul L, Klerks Paul L
Department of Biology, University of Louisiana at Lafayette, Louisiana 70504, USA.
Environ Toxicol Chem. 2007 Sep;26(9):1916-21. doi: 10.1897/06-589R.1.
Populations exposed to environmental contaminants can undergo intense selection pressures, which in turn can lead to a loss of genetic variation. We assessed this loss of genetic variation in the least killifish Heterandria formosa for laboratory populations that had undergone eight generations of selection for an increased resistance to cadmium. Using microsatellite markers, we compared genetic variation between three selection and three control laboratory populations and between these laboratory populations and the source population. Heterozygosity was lower in each selection population than it was in its paired control population, with this difference being statistically significant in two of the three comparisons. This is evidence that adaptation to environmental contaminants can result in an overall loss of genetic variation. Furthermore, the laboratory populations had much lower heterozygosity than did the source population. The latter loss of genetic variation, probably a result of random drift, did not prevent the laboratory populations from showing a strong response to the selection for cadmium resistance. The loss of genetic variation resulting from maintaining populations in the laboratory demonstrates that it is important to maintain a large population size for such populations and that the potential for loss of genetic variation in laboratory populations is taken into consideration in ecotoxicology when extrapolating from laboratory to natural populations.
接触环境污染物的种群可能会承受强烈的选择压力，这反过来又可能导致遗传变异的丧失。我们评估了在实验室种群中，经过八代镉抗性增强选择的细纹鳉（Heterandria formosa）的遗传变异丧失情况。我们使用微卫星标记，比较了三个选择实验室种群和三个对照实验室种群之间以及这些实验室种群与源种群之间的遗传变异。每个选择种群的杂合度都低于其配对的对照种群，在三个比较中的两个比较中，这种差异具有统计学意义。这证明了对环境污染物的适应会导致遗传变异的总体丧失。此外，实验室种群的杂合度远低于源种群。后一种遗传变异的丧失可能是随机漂变的结果，但这并没有阻止实验室种群对镉抗性选择表现出强烈反应。在实验室中维持种群导致的遗传变异丧失表明，对于此类种群而言，维持较大的种群规模很重要，并且在从实验室种群推断到自然种群时，生态毒理学研究应考虑实验室种群遗传变异丧失的可能性。
