The Biogeography ofPlantago ovataForssk. (Plantaginaceae)

Plantago ovataForssk. (Plantaginaceae) is a species that, in North America, inhabits desert and Mediterranean habitats of the southwest United States, northwest Mexico, and the Channel Islands of California and Mexico. In the Eastern Hemisphere,P. ovatainhabits desert regions ranging from the Canary Islands, across northern Africa to India. Previous authors have hypothesized thatP. ovatawas introduced to North America from Asia during the Miocene or introduced anthropogenically from Europe during the eighteenth century by Spanish settlers. We examined sequence data from the chloroplasttrnL‐trnF,trnS‐trnG, andpsbA‐trnHregions, the nuclear ribosomal internal transcribed spacer (ITS), and a putativeCYCLOIDEA‐like gene. Using a molecular clock based on an ITS calibration and a clock for plant chloroplast, we date a nonanthropogenic introduction event, from the Old World to North America, of ∼200,000–650,000 yr ago. On the basis of a morphological survey of 585 specimens from throughout the world range ofP. ovata, we suggest the recognition of four subspecific taxa. Phylogenetic analysis of chloroplast and ITS sequences supports this taxonomic treatment. Furthermore, morphological data and theCYCLOIDEA‐like gene sequences suggest the origin of North AmericanP. ovataas a result of hybridization between Old WorldP. ovatavarieties.