Contorted-pod evening-primrose (Camissonia contorta) COSEWIC assessment and status report: chapter 3

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Species Information

Name and classification

Macoun originally identified specimens of Camissonia contorta collected in BC in the late 1880’s as Oenothera strigulosa (Fischer and Meyer) Torrey and A. Gray. All three of his specimens have been annotated as Camissonia contorta by reliable taxonomists.

Most contemporary taxonomists recognize Camissonia contorta ias a distinct taxon and there are no infraspecific taxa recognized in Canadawith nosubspecies or varieties. Camissonia pubens (S. Wats.) Raven is a closely-related species that is occasionally treated as C. contorta var. pubens Kearney. Camissonia. pubens is restricted to California and Nevada.

Morphological description

Camissonia contorta (Figure 1) is a slender, usually diminutive annual herb, occasionally growing to 40 cm long, arising from a slender taproot. Its stem is wiry, usually branched, peeling below and often sprawling. The stem bears coarse, spreading hairs and the plant may be glandular-hairy in the inflorescence. Its leaves are linear to narrowly elliptic, 5-30 mm long and entire to remotely toothed. The flowers are arranged in a leafy-bracted, nodding, terminal raceme. The flowers are borne on a short stalk or are unstalked. Each flower consists of a hypanthium 1.5-2.0 mm long that bears four sepals, four petals, eight anthers and an inferior ovary. The sepals are 2.5-4.0 mm long and are reflexed at maturity. The petals are 3-5 mm long and yellow, fading to red. The stamens are noticeably unequal, the longer set nearly twice the length of the shorter. The ovary is 4-chambered and matures into a linear, 2-4 cm long capsule scarcely 1 mm thick. The unstalked capsule is cylindrical and swollen about the seeds and varies from nearly straight to arching almost into a coil. There is 1 row of seeds per chamber and the seeds are 0.7 – 0.9 mm long, shiny and minutely pitted (Douglas and Meidinger 1999). The stems, leaves and capsules are often deep red, particularly in unshaded environments.

Figure 1. Camissonia contorta; flower, fruit and general plant habit (Illustrated by Jeanne R. Janish with permission from University of Washington Press).

Genetic description

The genus Camissonia has a base chromosome number of x=7. Aneuploidy is almost unknown in Camissonia, but occurs in other genera in the Onagraceae. Camissonia contorta is the only hexaploid species in the section Camissonia (n=21), based on chromosome counts from 40 populations, including specimens from two locations in British Columbia. This species may form sterile hybrids with the diploid C. campestris and the tetraploid C. strigulosa (neither of which occur in Canada) and may be an allopolyploid derived from hybridization between these two taxa. Alternatively, it may have arisen from the fertilization of unreduced gametes in a tetraploid species such as C. strigulosa (autopolyploidy). There is no evidence of intergradation between C. contorta and any other species throughout its range (Raven 1969).