南美古柯(Erythroxylumcoca和E.novogranatense)已成为许多安第斯和亚马逊社区的基石作物至少8000年。然而,在过去的半个世纪里,全球对其生物碱可卡因的需求推动了这种植物的集约化农业,并将其置于武装冲突和森林砍伐的中心。为了监测古柯种植园不断变化的景观,联合国毒品和犯罪问题办公室收集其种植地区的年度数据。然而,由于鉴定方面的限制,试图划定不同品种种植的地区的尝试失败了。在没有鲜花的情况下,识别依赖于叶片形态,然而,这在分类学中的反映程度尚不确定。这里,我们分析了古柯及其四个最接近的野生近亲(“古柯进化枝”)的当前命名系统的一致性,使用形态计量学,系统基因组学,分子钟,和人口基因组学。我们包括古柯最接近的野生亲戚E.gracilipes和E.caparactarum的带有名称的标本。342个数字化植物标本室标本的形态计量学表明,叶片的形状和大小无法可靠地区分物种和品种。然而,统计分析表明,某些品种的更圆和更倒卵形的叶子可能与古柯微妙的驯化综合症有关。我们的系统发育数据表明,广泛的基因流涉及E.gracilipes,结合形态计量学,支持E.gracilipes保留为单一物种。为古柯进化枝建立强大的进化分类框架将有助于开发具有成本效益的基因分型方法,以支持可靠的鉴定。
South American coca (Erythroxylum coca and E. novogranatense) has been a keystone crop for many Andean and Amazonian communities for at least 8,000 years. However, over the last half-century, global demand for its alkaloid cocaine has driven intensive agriculture of this plant and placed it in the center of armed conflict and deforestation. To monitor the changing landscape of coca plantations, the United Nations Office on Drugs and Crime collects annual data on their areas of cultivation. However, attempts to delineate areas in which different varieties are grown have failed due to limitations around identification. In the absence of flowers, identification relies on leaf morphology, yet the extent to which this is reflected in taxonomy is uncertain. Here, we analyze the consistency of the current naming system of coca and its four closest wild relatives (the \"coca clade\"), using
morphometrics, phylogenomics, molecular clocks, and population genomics. We include name-bearing type specimens of coca\'s closest wild relatives E. gracilipes and E. cataractarum.
Morphometrics of 342 digitized herbarium specimens show that leaf shape and size fail to reliably discriminate between species and varieties. However, the statistical analyses illuminate that rounder and more obovate leaves of certain varieties could be associated with the subtle domestication syndrome of coca. Our phylogenomic data indicate extensive gene flow involving E. gracilipes which, combined with
morphometrics, supports E. gracilipes being retained as a single species. Establishing a robust evolutionary-taxonomic framework for the coca clade will facilitate the development of cost-effective genotyping methods to support reliable identification.