Whitehead Andrew, Anderson Susan L, Kuivila Kathryn M, Roach Jennifer L, May Bernie
Bodega Marine Laboratory, University of California-Davis, PO Box 247, 2099 Westside Road, Bodega Bay, CA 94923-0247, USA.
Mol Ecol. 2003 Oct;12(10):2817-33. doi: 10.1046/j.1365-294x.2003.01933.x.
Exposure to contaminants can affect survivorship, recruitment, reproductive success, mutation rates and migration, and may play a significant role in the partitioning of genetic variation among exposed and nonexposed populations. However, the application of molecular population genetic data to evaluate such influences has been uncommon and often flawed. We tested whether patterns of genetic variation among native fish populations (Sacramento sucker, Catostomus occidentalis) in the Central Valley of California were consistent with long-term pesticide exposure history, or primarily with expectations based on biogeography. Field sampling was designed to rigorously test for both geographical and contamination influences. Fine-scale structure of these interconnected populations was detected with both amplified fragment length polymorphisms (AFLP) and microsatellite markers, and patterns of variation elucidated by the two marker systems were highly concordant. Analyses indicated that biogeographical hypotheses described the data set better than hypotheses relating to common historical pesticide exposure. Downstream populations had higher genetic diversity than upstream populations, regardless of exposure history, and genetic distances showed that populations from the same river system tended to cluster together. Relatedness among populations reflected primarily directions of gene flow, rather than convergence among contaminant-exposed populations. Watershed geography accounted for significant partitioning of genetic variation among populations, whereas contaminant exposure history did not. Genetic patterns indicating contaminant-induced selection, increased mutation rates or recent bottlenecks were weak or absent. We stress the importance of testing contaminant-induced genetic change hypotheses within a biogeographical context. Strategic application of molecular markers for analysis of fine-scale structure, and for evaluating contaminant impacts on gene pools, is discussed.
接触污染物会影响生物的生存、补充、繁殖成功率、突变率和迁移，并可能在暴露和未暴露种群之间的遗传变异分配中发挥重要作用。然而，应用分子群体遗传学数据来评估此类影响并不常见，而且往往存在缺陷。我们测试了加利福尼亚中央谷地本地鱼类种群（萨克拉门托吸口鱼，Catostomus occidentalis）的遗传变异模式是否与长期农药暴露历史一致，或者主要是否符合基于生物地理学的预期。实地采样旨在严格测试地理和污染的影响。利用扩增片段长度多态性（AFLP）和微卫星标记检测了这些相互连接种群的精细结构，并且两种标记系统所阐明的变异模式高度一致。分析表明，生物地理学假设比与共同历史农药暴露相关的假设能更好地描述数据集。无论暴露历史如何，下游种群的遗传多样性都高于上游种群，并且遗传距离表明来自同一河流系统的种群倾向于聚集在一起。种群之间的亲缘关系主要反映了基因流动的方向，而不是暴露于污染物的种群之间的趋同。流域地理因素导致了种群间遗传变异的显著分配，而污染物暴露历史则没有。表明污染物诱导选择、突变率增加或近期瓶颈效应的遗传模式很微弱或不存在。我们强调在生物地理学背景下测试污染物诱导的遗传变化假设的重要性。讨论了分子标记在分析精细结构以及评估污染物对基因库影响方面的战略应用。
