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Wolf's evening primrose recovery efforts
New population establishment
Oenothera wolfii in the greenhouse
Planting Oenothera wolfii
Oenothera hybrid zone
Left: Oenothera wolfii plants growing in the greenhouse (photo by ODA staff). Middle: Volunteers outplanting O. wolfii seedlings at new experimental population site south of Gold Beach (photo by Melissa Carr). Right: Putative hybrid between O. wolfii and O. glazioviana (photo by ODA staff). If downloading images from this website, please credit the photographer.

Project goal
To promote the recovery of Wolf's evening primrose by:
  • Investigating hybridization threats to the species
  • Providing basic biological and ecological information necessary for developing management, conservation, and recovery strategies
  • Developing seed germination and greenhouse cultivation methods
  • Creating two new populations on protected, publicly owned land

Project duration
1999-2005

Background
Wolf’s evening primrose (Oenothera wolfii), a rare member of the family Onagraceae, occurs in only sixteen known locations on the southern Oregon and northern California coast. This species currently faces many threats, including loss and degradation of habitat due to development, dune stabilization, road maintenance, and invasions of exotic species. Additionally, hybridization with the escaped garden ornamental, Oenothera glazioviana, may be undermining the genetic integrity of this rare species. In response to these threats, the ODA listed Wolf's evening primrose as threatened in 1995.

Summary
  • Hybridization study: In 2000, ODA staff, in partnership with U.S. Fish and Wildlife Service and Oregon State University, developed a research protocol to attempt to identify which coastal Oenothera populations were composed of "pure" O. wolfii, and which populations were of hybrid origin. Measurement of thirteen quantitative characteristics documented extensive morphological variation among populations, suggesting that hybridization and introgression between the rare Wolf’s evening primrose and the introduced exotic is a common occurrence.

  • Reproductive ecology, seed germination, and cultivation study: Starting in 1999, ODA staff investigated potential reproductive limitations facing Wolf’s evening primrose by looking at the mating system, seed production, and seed germination biology of this species. Wolf’s evening primrose flowers that were covered with pollinator exclusion bags produced ample fruits and seeds, indicating that this species is self-compatible. On average, an O. wolfii plant produced over 28,000 seeds. The seeds of this species germinate readily in the greenhouse, and do not appear to require pretreatment. Oenothera wolfii is also fairly easy to cultivate. Seed collected in 1999 was used to grow O. wolfii in the greenhouse, where it was determined that a 4-6 week cold period is needed for the plants to flower.

  • Creation of experimental populations: The Native Plant Conservation Program worked with many partners (Bureau of Land Management, U.S. Fish and Wildlife Service, Oregon State University, the Native Plant Society of Oregon, the Oregon Department of Transportation) on Wolf's evening primrose introduction efforts. Using seeds collected in the fall of 2002, O. wolfii plants were cultivated in the greenhouse the following summer. In the fall of 2003, two experimental populations of Wolf's evening primrose were outplanted on the southern Oregon coast on protected lands. Initial results are promising, with high transplant survival and reproduction rates.

Future work
Future monitoring is needed to assess the long-term success of experimental populations. Oregon populations need to be periodically assessed for signs of hybridization.

Reports
Oenothera wolfii 2003 reintroduction project report (pdf document, 1.25 MB)
 
 
For more information about this species, visit the Wolf's evening primrose plant profile.