The promotion of responsible and sustainable trade in biological resources is widely proposed as one solution to mitigate currently high levels of global biodiversity loss. Various molecular identification methods have been proposed as appropriate tools for monitoring global supply chains of commercialized animals and plants. We demonstrate the efficacy of target capture genomic barcoding in identifying and establishing the geographic origin of samples traded as Anacyclus pyrethrum, a medicinal plant assessed as globally vulnerable in the IUCN Red List. Samples collected from national and international supply chains were identified through target capture sequencing of 443 low-copy nuclear makers and compared to results derived from genome skimming of plastome, standard plastid barcoding regions and ITS. Both target capture and genome skimming provided approximately 3.4 million reads per sample, but target capture largely outperformed standard plant DNA barcodes and entire plastid genome sequences. Despite the difficulty of distinguishing among closely related species and infraspecific taxa of Anacyclus using conventional taxonomic methods, we succeeded in identifying 89 of 110 analysed samples to subspecies level without ambiguity through target capture. Furthermore, we were able to discern the geographical origin of Anacyclus samples collected in Moroccan, Indian and Sri Lankan markets, differentiating between plant materials originally harvested from diverse populations in Algeria and Morocco. With a recent drop in the cost of analysing samples, target capture offers the potential to routinely identify commercialized plant species and determine their geographic origin. It promises to play an important role in monitoring and regulation of plant species in trade, supporting biodiversity conservation efforts, and in ensuring that plant products are unadulterated, contributing to consumer protection.
Retracing pathways of historical species introductions is fundamental to understanding the factors involved in the successful colonization and spread, centuries after a species’ establishment in an introduced range. Numerous plants are thought to have been introduced to regions outside their native ranges by European voyagers and early colonists making transoceanic journeys; however, records are scare to document this. We use genotyping-by-sequencing and genotype-likelihood methods on the selfing, global weed, Plantago major, collected from 50 populations worldwide to test hypotheses that the plant was brought to new regions during colonial times. We further investigate how patterns in genomic diversity facilitate the success of this global weed. Although genomic differentiation among populations is found to be low, we identify six unique ecotypes showing very little sign of admixture. Three of the most prevalent of these ecotypes present in the native range gave rise to introduced populations in the Americas, Africa, Australia and New Zealand, indicating that more than one successful ecotype colonized and spread. The distribution of ecotypes is found to have links to colonial history, and ecotypes are further found to be restricted by latitude. Dispersal of multiple successful ecotypes and prior adaptation in the native range to latitudinally dependent environmental factors (such as climate) are likely reasons for the success of this prolific, global weed. Genomic signatures can provide new perspectives on the drivers behind the historic introductions and the successful colonization of introduced species in an era of global change.