Assigning African elephant DNA to geographic region of origin: Applications to the ivory trade
Assigning African elephant DNA to geographic region of origin: Applications to the ivory trade
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DOI：
10.1073/pnas.0403170101
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发表时间：
2004-10-12
影响因子：
11.1
通讯作者：
Stephens, M
中科院分区：
文献类型：
--
作者：
Wasser, SK;Shedlock, AM;Stephens, M
非洲象牙非法贸易的卷土重来将大象置于新的危险之中。通过能够核实象牙的地理来源，可以极大地改善对这种贸易的监管。我们开发了一种遗传和统计相结合的方法来确定偷猎象牙的来源，以满足这一需求。我们的统计方法利用一种平滑方法来估计整个非洲大象范围内16个微卫星座位的地理特定等位基因频率，使用来自28个地点的森林大象(Loxodonta Africana Cyc1otis)和草原大象(Loxodonta Africana Africana)的315个组织和84个粪便样本。这些地理上特定的等位基因频率估计被用来推断DNA样本的地理来源，例如可以从未知来源的象牙中获得。我们证明，在这种情况下，我们的方法缓解了与标准分配方法相关的几个问题，并且我们的方法的绝对精度很高。在整个大陆范围内，50%的样本位于500公里以内，80%位于实际原产地932公里以内。精度因区域而异(精度中位数：西非135公里；中部萨凡纳286公里；中部森林411公里；南部697公里)。在某些情况下，等位基因频率在小的地理区域上差异很大，使得更精细的区分成为可能，并表明从我们研究中没有代表的地点收集样本可以进一步提高分辨率。
Resurgence of illicit trade in African elephant ivory is placing the elephant at renewed risk. Regulation of this trade could be vastly improved by the ability to verify the geographic origin of tusks. We address this need by developing a combined genetic and statistical method to determine the origin of poached ivory. Our statistical approach exploits a smoothing method to estimate geographic-specific allele frequencies over the entire African elephants' range for 16 microsatellite loci, using 315 tissue and 84 scat samples from forest (Loxodonta africana cyc1otis) and savannah (Loxodonta africana africana) elephants at 28 locations. These geographic-specific allele frequency estimates are used to infer the geographic origin of DNA samples, such as could be obtained from tusks of unknown origin. We demonstrate that our method alleviates several problems associated with standard assignment methods in this context, and the absolute accuracy of our method is high. Continent-wide, 50% of samples were located within 500 km, and 80% within 932 km of their actual place of origin. Accuracy varied by region (median accuracies: West Africa, 135 km; Central Savannah, 286 km; Central Forest, 411 km; South, 535 km; and East, 697 km). in some cases, allele frequencies vary considerably over small geographic regions, making much finer discriminations possible and suggesting that resolution could be further improved by collection of samples from locations not represented in our study.