Plantago ovata Forssk. (Plantaginaceae) is a winter annual species which, 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. ovata inhabits desert regions ranging from the Canary Islands, across
northern Africa to western India. The wide disjunction between P. ovata in the western
and eastern hemispheres poses an interesting question as to the origin and biogeography
of the species. Previous authors have hypothesized that P. ovata was introduced to North
America over the Bering land bridge, from Asia, during the Miocene, or introduced
anthropogenically from Europe during the 18th century by Spanish settlers. In this study
we examined sequence data from the chloroplast trnL-trnF, trnS-trnG and psbA-trnH
regions, the nuclear ribosomal internal transcribed spacer (ITS) and a region 5' of the
TCP region of a CYCLOIDEA gene. Using a molecular clock based on an ITS calibration
within the Plantago genus, and a clock for plant chloroplast, we date a non-anthropogenic
introduction event, from the Old World to North America, approximately
200,000-650,000 years ago. This is consistent with a Pleistocene origin, and does not
support a Miocene origin of the disjunction. Based on a morphological survey of 552
specimens, from throughout the world range of P. ovata, we suggest the recognition of
four subspecific taxa. Molecular phylogenetic analysis of chloroplast DNA and nuclear
ribosomal DNA ITS sequences support this taxonomic treatment. Furthermore,
phylogenetic sequences of the CYCLOIDEA gene support the morphological data. Both
suggest the origin of North American P. ovata as a result of hybridization between Old
World P. ovata varieties. This event provides further evidence that hybridization may
serve as a predictor of invasiveness in plants. / Graduation date: 2005
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/29677 |
| Date | 09 March 2005 |
| Creators | Meyers, Stephen C. |
| Contributors | Liston, Aaron |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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