Contorted-pod evening-primrose (Camissonia contorta) COSEWIC assessment and status report: chapter 6
Biology
Little has been written about the biology of Camissonia contorta, apart from the taxonomic treatment Raven (1969) provides for the genus. The following information, unless otherwise cited, is based on unpublished field observations and garden experiments conducted by Matt Fairbarns.
Life cycle and reproduction
Camissonia contorta is a short-lived annual. In natural populations, germination begins in March or April and appears to end in May. Garden experiments demonstrated that current-year seeds are capable of germinating in mid-summer if watered. Despite frequent visits in 2003 and 2004, no seedlings were observed in the field later than May in either population 1 or 2.
Flowering begins in April and peaks in June. Raven (1969) describes Camissonia contorta as self-fertilizing but provides no supporting evidence. Camissonia contorta is a polyploid annual with small and inconspicuous flowers and such plants tend towards self-fertilization. On the other hand, it has perfect flowers and a relatively large stigmatic surface, features often associated with cross-fertilization. At one of the survey sites, a small beetle bearing abundant pollen on its body was observed crawling over the stigmatic surface of C. contorta, suggesting cross-pollination is possible. In fact, almost all angiosperm plants including many described as self-fertilizing, are capable of at least low levels of cross-fertilization. Based on this evidence, it appears that most flowers of Camissonia contorta are probably self-pollinated but cross-pollination occurs fairly regularly.
Seed dispersal begins in early May and most plants have shed their seed by late July. All of the Canadian populations have similar fecundity. Plants tend to produce between 3 and 10 capsules although some reproductive plants produce as few as 1 or as many as 17 capsules. Most capsules contain 10-20 ripe seeds at maturity.
Camissonia contorta, as a taprooted and usually short-lived annual, is incapable of clonal growth or asexual reproduction.
Plants continue to grow until they succumb to summer drought. Mortality normally occurs in June or July but summer rainfall events may trigger renewed vegetative growth, flowering and fruiting. In favorable years, a small proportion of plants may continue to flower until October, when cool weather appears to end growth.
Herbivory/predation
There was no information available on herbivory during the seedling stage. Light levels of foliar herbivory were noted in established plants but non-native herbivores appeared to be responsible; such observations are discussed in the section dealing with “Limiting Factors and Threats”.
Physiology
Camissonia contorta survives summer drought and winter cold by persisting as seeds.
Dispersal/migration
Seeds of Camissonia contorta lack any apparent adaptations to assist in long-distance dispersal. Observations of dehiscing fruit suggest that most seeds likely remain in the immediate vicinity (within 20 cm) of the parent plant. The species persists in the same location year after year, rather than forming source-sink populations or metapopulations. Seeds may be transported in sand during blow-out events, which may result in occasional dispersal for several metres. The short distances of seed dispersal and the strong tendency towards autogamy suggest that there is little potential for a rescue effect, even over the short distances between populations.
Interspecific interactions
There are no known interspecific interactions that increase the susceptibility of Camissonia contorta to extirpation in Canada.
Adaptability
Camissonia contorta is poorly adapted to moving sand, migration, as the plants are low and can be quickly are buried by shifting sand. Its tiny seeds lack abundant endosperm reserves (pers. obs.), so it is unlikely to establish if they are covered by more than a few millimetres of sand. The same limitations render the species susceptible to human disturbances that lead to shifting sand. Propagation experiments (pers. obs.) revealed that a high proportion of seeds germinate readily; however, seedling mortality was high. Transplanting has not been attempted. The species' reliance on a very deep taproot, the fact that it is an annual, and its specialized habitat requirements suggest that transplantation from horticultural sources would be unsuccessful.
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