Climbing prairie rose (Rosa setigera) COSEWIC assessment and status report addendum: chapter 9
Biology
General
Climbing prairie rose is an arching/climbing shrub of old fields and shrub meadows. Its long arching branches and recurved prickles allow it limited climbing ability over other shrubs, but often it is suppressed and ultimately shaded out as nearby shrub growth becomes dense. It is dioecious (Kevan et al., 1990), an unusual condition in roses. Fruit develops on the females and is likely dispersed by birds and small mammals. First year seedlings were not seen in the field surveys, but in a few old fields recently released from cultivation juvenile plants were observed near mature populations. Limited vegetative proliferation occurs from the tips of arching stems.
Reproduction
Flowers are visited by a diversity of pollinating insects, mostly bees and flies. Plants were found to be cryptically dioecious (i.e., male and female plants have morphologically similar flowers). Both males and females produce pollen, although the pollen on the female flowers was not functional in stimulating fruit production in other plants and male plants produce no fruit (Ambrose & Kevan, 1990; Kevan et al., 1990). Being functionally dioecious, isolated individuals are not able to produce fruit. The fruit is a hip, typical of roses, with a fleshing receptacle enclosing hairy achenes. Clonal reproduction is occasionally seen around older plants, in the form of new plantlets developing where the tips of branches touch the ground.
Survival
As a species of early successional or open communities, individuals can be short lived (perhaps 10-20 years) unless conditions are present which keep the habitat open. Where plants were found in the same location as the previous survey in the early 1980s the stems were relatively young indicating new growth from the crown, vegetative plantlets or locally dispersed seeds rather than persistent old stems. Where shrubby vegetation becomes dense this species is suppressed, fails to flower and dies out. In dense vegetation it also appears to be more prone to mildew. In 2000, mildewed flower buds were observed on this species in two dense shrub meadows with several individuals each; they failed to open and no fruit was produced.
Dispersal
The firm fleshy reddish-orange fruit, containing hard seeds, are likely dispersed by birds and mammals. When seed sources are nearby young plants have been observed in old fields in early stages of succession, leading to the conclusion that dispersal is effectively taking place. The rarity of this species in the states to the south and west reduces the likelihood of long distance dispersal into Ontario.
Nutrition and interspecific interactions
Pollinating insects and seed dispersers are important for fruit set and seed dispersal to new habitats. Flowers of both male and female plants produce pollen, gathered by pollinating insects, but no nectar. While the pollen of female flowers is non-functional for stimulating fruit production, it appears to provide a nutritional reward to the insects.
Invasive exotic shrubs are seen in some habitats (e.g., Elaeagnus umbellatus) and could become significant competitors. For this species of open habitats, natural succession can also reduce the suitability of sites.
Adaptability
Most populations occur in old fields and shrub meadows on heavy soils. A few also occur on sand (Pt. Pelee, Ojibway Prairie and LaSalle) and thin soil over limestone (Stone Road Alvar).
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