Travel tales of a worldwide weed: genomic signatures reveal colonial
trade routes and prior adaptation are key to the success of
Plantago major
Abstract
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.